BREEDING BIOLOGY AND ECOLOGY OF THE

BREEDING BIOLOGY AND ECOLOGY OF THE SEABIRDS OF JOHNSTON ATOLL, CENTRAL PACIFIC OCEAN: results of a long-term monitoring project 1984-2003

Report submitted to Project Manager for Chemical Stockpile Demilitarization Aberdeen Proving Ground, Maryland

December 2003 Elizabeth A. Schreiber, Ph.D. Bird Department, MRC 116 National Museum of Natural History Smithsonian Institution, Washington, DC 20560 PH 703768-6726 FAX 703768-9010 [email protected]

Johnston Atoll Seabirds 2003 - Schreiber

TABLE OF CONTENTS

SUMMARY

4

INTRODUCTION

7

HISTORICAL DATA

10

OBJECTNES

17

METHODS

19

RESULTS AND DISCUSSION

22

Counts Potential JACADS Effects on Birds Reproductive Success and Survival of Tropicbirds Growth Rates of Chicks Adult Mass and Egg Mass Solid Waste Management Units EL Nifio Effects Delayed Timing of Nesting in 1991 Historical Mortality from LORAN-C Tower Estimating Nest Success Migration Artificial Nest Sites Description of Nesting Habitat Vegetation Control, Modification, & Planting Runway Vegetation Clearing Heavy Metal Analyses Lagoon Monitoring for Seabird Feeding Activity

24 25 27 46 48 50 50 56 57 58 59 61 63 66 67 69 70 78

INDNIDUAL SPECIES ACCOUNTS Bulwer's Petrel Wedge-tailed Shearwater Christmas Shearwater Red-tailed Tropicbird White-tailed Tropicbird Masked Booby Brown Booby Red-footed Booby

78 79 81 82 94 95 97 \03 2


Great Frigatebird Sooty Tern Brown Noddy Black Noddy White Tern Gray-backed Tern Blue-gray Noddy

',"-,,-

110

115 119 121 124 126 128

CONCLUSIONS: the future of Johnston Atoll birds

128

BIBLIOGRAPHY

133

TABLES AND FIGURES

142

APPENDIX A: Reconunendations for closure procedures to benefit seabirds. APPENDIX B: Analysis of survival in Red-tailed Tropicbirds nesting upwind and downwind ofthe JACADS incinerator (Schreiber et a!. 2001). APPENDIX C: Testing life history predictions in a long-lived seabird: a population matrix approach with improved parameter estimation. (Doherty et a!., 2004)

3


BREEDING BIOLOGY AND ECOLOGY OF THE SEABIRDS OF JOHNSTON ATOLL, CENTRAL PACIFIC OCEAN:

results of a long-term monitoring project: 1984-2003

SUMMARY This year, 2003, brings to a conclusion 20 years of detailed study of the Johnston Atoll avifauna. The study was carried out to mpnitor the breeding biology and ecology of the seabirds of Johnston Atoll in order to determine ifthere were any effects on them from the Johnston Atoll Chemical Agent Disposal System (JACADS). JACADS is now closed down and the final clean-up is underway. Culminating this milestone, and documented by very thorough, consistent and detailed monitoring, is the fact that the incineration process did not cause any problems to the birds of Johnston Atoll. In fact, throughout the incineration of chemical weapons, population levels (a frequently used indicator of a species' health) of all thirteen nesting species increased dramatically. Additionally, this study has not only made Johnston Atoll one of the best studied seabird colonies in the world, it has revealed many previously unknown facts about the breeding biology of seabirds. It has also corrected many misconceptions and incorrect information about seabird biology that are in the old literature. This last year of monitoring has seen a continuation of the normal, high reproductive success of all thirteen breeding species on Johnston Atoll (see descriptions under species accounts below). During the beginning of the year, the 2002 El Nino was still affecting some of the species but by June the event was over. This event had particularly strong effects on the birds during 2002 and 4


early 2003, and nesting populations were down in several species. This is a normal response for seabirds during an EI Nino; fewer than normal numbers of birds attempt to breed. But during 2003 as the event dissipated, the nesting population again increased. Some nesting habitat was lost during 2002 and 2003 on Sand and North Islands where buildings and bunkers were removed. Bushes that had supported about 50 red-footed booby (Sula sula) nest sites around the buildings on Sand Island were destroyed during building demolition. Bushes around the buildings on North Island were undisturbed during demolition, but were basically destroyed by the end of the year. The buildings had protected one side of the bushes and provided extra rain water runoff from the roof. Once the birds could nest on both sides of the bushes and the extra rain water was lost, the bushes could not survive the density of nesting boobies. More bird habitat will be lost on Johnston Island during 2004 as areas of bushes are used to store demolished buildings which are then to be covered with coral sand. In recent years Bristle-thighed Curlews (Numenius tahitiensis) have caused a large loss of

tropicbird eggs on Johnston Island. Bristle-thighs have learned to sneak in and steal an egg any time it is exposed (as when adults change over incubation duties or fight over a territory). They took an estimated 150 tropicbird eggs during 2003. The curlews, and Ruddy Turnstones (Arenaria interpres), have been eating tern eggs on the Atoll for years. Curlew egg predation, added to the continuing nest site loss for tropicbirds owing to red-footed boobies and great frigatebirds (Fregata minor), has reduced the potential nesting population of tropic birds on the atoll by about 35-40% over the years, much more so than any human impact. None of the species nesting on Johnston Atoll is considered endangered or threatened. Most are pan-tropical nesters, occurring in tropical waters throughout the world. All these species have reproductive lives of 20 - 30 years (Schreiber and Burger 2001, Appendix B). The 5


high nest success during the operation of JACADS illustrates that activities of this type can be compatible with preserving wildlife when undertaken with proper precautions and concern. The bird populations of Johnston Atoll serve as a sensitive indicator to the continuing health of the environment of the Atoll and the surrounding ocean. Seabirds are a top-level carnivore, similar to man, and are susceptible to the same perturbations in the environment as is man. Birds, being smaller however, are more sensitive and can serve as a warning indicator for man. These studies have shown no effect of the JACADS operation on bird populations, other than the loss of a few nest sites. In comparisons between birds nesting downwind of the plant and those nesting in a control site, there are no differences in any of the parameters monitored (egg size, nest success, adult mass, growth rates of young, recruitment rates of young, survival of adults: see Appendix B this report and Schreiber et al. 2001). With the amount of banding accomplished over the years of this study, and subsequent band recoveries of birds from year to year (to determine recruitment and survival rates), the detailed counts of the numbers of nesting birds and estimates of nest success, we have documented the longterm population dynamics of the seabirds on Johnston Atoll. The birds of Johnston Atoll have been well protected from introduced predators and from man, and have had concomitant high nest success rates since this study began in 1984. With the JACADS mission complete and the military closing down operation on the Atoll, the birds will have the atoll to themselves in the future. We do not expect any change in the normal high reproductive success or in survival rates. Population levels may continue to increase and more species may eventually begin nesting on Johnston Island itself.

6


INTRODUCTION During 2003 we continued to monitor the ecology, breeding biology and nesting success 0

of the seabird populations of Johnston Atoll (16 45'N, 1690 31'W). This study was carried out in order to determine if the operation of the JACADS project (Johnston Atoll Chemical Agent Disposal System) and the human population of the Atoll had any affect on the bird populations. Marine birds (a top level predator) serve as a very sensitive, highly visible indicator of the health ofthe marine environment as well as to their land based environment. This report for 2003 is a summary of 20 years of research on the birds of Johnston Atoll in relation to the construction, operation and closure ofthe JACADS project. We made three visits to the Atoll during 2003: in March, June and August. Construction for JACADS began in 1986 and limited operation of the plant began during 1991. Incineration of chemical weapons was completed during December 2000. By the end of 2003, final clean-up for the project was essentially complete. Part of the clean-up included demolishing the buildings along scientific row that were part ofthe nuclear missile testing program during the 1960's, returning the area to a natural state. The incinerator site itself is reduced to a small amount of clean rubble buried under an approximately 8 foot high mound of coral rubble. Throughout the incineration process and during the closure process there have been no measurable effects on the birds as a result of plant operation. Birds nesting downwind of the plant exhibit the same nest success, same chick growth rates, same adult masses, same recruitment rates, and same survival rates as do birds nesting elsewhere on the Atoll in

7


Old site of JACADS incinerator building along south side of Johnston Island. September 2003. A 7 foot high cap of coral sand covers some clean rubble from the building demolition.

upwind areas. The human population on the Atoll has caused no measurable decrease in numbers of nesting birds or in fledging success of young, in fact, the nesting populations of all species increased in numbers over this twenty year period (population size is a common endpoint monitored by the EPA to determine environmental health.). Humans not only represented a source of potential physical disturbance to nesting birds, but the increased dumping of organic sewage and waste in the local waters could have harmed the birds' food source, fish and squid. This does not appear to have affected the birds either given their growing populations and high nest success. The main human disturbance to birds between 1984 and 2003 was the demolition of over 1300 tropicbird nest sites on Johnston Island owing to: I) JACADS construction activities (about 200 ncsts), 2) clearing the LE-2 area for clean-up of plutonium (about 200 nests), 3) clearing vegetation from the airfield fringes (about 700 nests), and 4) destruction of the trees and bushes in the HO Site during cleanup ofthat site (200 nests). Birds that lose their nest site do not readii y re·· g

Johnston Atoll Seabirds 2003 - Scbreiber

nest elsewhere so the loss of a nest site frequently represents the loss of that pair to the breeding population (see discussion under the tropicbird species account below). During 1997 the number of birds flying over the runway became a cause for concern and clearing of vegetation along the runway north side was begun in December. About 75-90 nest sites were destroyed at that time to lessen the air-strike hazard During 1998-99 about 650-700 nest sites were destroyed when more vegetation along the runway was cleared away to prevent birds from nesting there (See discussion under Runway Vegetation Clearing below). At the same time, nesting and roosting red-footed boobies and great frigatebirds have destroyt;ld 90% of the nesting habitat used by tropicbirds on North and Sand Islands. These two islands lost a total of over 1200-1400 tropicbird nest sites. Our studies concentrated primarily on the Pelecaniform species nesting on the Atoll because they can be caught, banded in large numbers and recaptured to track individuals from year to year with no effect on nesting success. Only by knowing what individual birds are doing can the longterm effects of any potential perturbation be determined. We have monitored egg size, adult mass, growth and development of chicks, marked individual nest sites, individually banded adults and chicks, and estimated each species' population size and fledging success as closely as possible. Over the years we estimated the number of nests of other species using the Atoll. Die-offs of young or adults, a change in growth rates of young, changes in adult masses and changes in numbers of birds nesting or fledging from year to year can all be indicators of a perturbation occurring to bird populations. Between 1985 and 1990, the human population of the Atoll quadrupled and over the past 20 years, the nesting populations of tropic birds, brown boobies, red-footed boobies and several other species followed suit (Table I; Figs. 31, 34 - 36) further illustrating that birds and man can co-exist 9


when the proper precautions are taken.

HISTORICAL DATA Two highly modified natural islands (Johnston and Sand), and two entirely man-made islands (North and East) compose the land mass of Johnston Atoll. President Calvin Coolidge declared the Atoll a National Wildlife Refuge in 1926 and its wildlife, especially the bird populations, have been protected since that time. Excellent historical data on wildlife exist for the Atoll from Biological Survey Reports for 1923 and from the Pacific Ocean Biological Survey Reports (POBSP) of the Smithsonian Institution, whose personnel occupied Sand Island continuously from 1963 through 1968 (Amerson and Shelton 1976). Since then several less extensive studies have been carried out on the birds: I) B. Harrington on sooty terns from 18 March - 3 June 1971, and 2) A. Binion Amerson from 6 - 12 November 1973 (Amerson and Shelton 1976). In the early 1980's Fish and Wildlife Service FWS) personnel made a few visits to the Atoll and recorded incidental observations of the birds. Some of these visits were during October when nesting is greatly reduced, thus the data don't reflect real popUlations of the Atoll. We include counts ofthe above visits for reference (Table la). From 1986 through 2003 the FWS (Hawaiian Islands National Wildlife Refuge) had a refuge manager stationed on the Atollwith the help of funding from the Department of Defense. Through the years the different refuge managers carried out different monitoring protocols. Their data may be obtained from the Hawaii office of the U. S. Fish and Wildlife Service.

Following are documentary photographs of Johnston and the outlying islands.

10


Johnston Island, looking west from roof of JOe bnilding down runway. 2001. Much of the island is hard packed coral sand road bed which will take many years to grow plants.

Johnston Island from JOe roof looking to NW. 2001. Most bushes or trees on the island have tropicbirds nesting under them and many have white terns nesting on the limbs. 11


Johnston Island from JOC roof to North. 2001. Ballpark and area to the right will be buried under rubble and covered with coral sand. Approximately 50 tropicbird nest sites are being destroyed.

Bunkers on west end of Johnston Island. June 2003. Once, used for storage of nerve gas munitions, now filled with rubble from JACADS deconstruction. This rubble will help keep the bunkers from eventually caving in on top and becoming a trap for birds. 12


Johnston Island from the air terminal toward the pool (to north, north-west). June 2003. Bush-tree habitat along north side of runway (part of the original island) is used heavily by tropicbirds, white terns, and black noddies for nesting. These buildings are on the rise that is the original part of Jl before dredging.

Johnston Island from JOC roof toward southeast end. 2001. Pluchea bushes to left, used heavily by tropicbirds. Casurina (introduced species) is little used by birds: a few tropicbirds, white terns and black noddies nest in them. Photo shows large area of runway and road (some blacktop, some hard packed coral sand. Coral saqd road areas will not grow bushes that are useful for bird habitat for 10-IS years.

13


Bushes on southeast end of Johnston Island are heavily used by tropicbirds for nesting. Extensive road surfaces are hard packed coral sand and will not grow usefnl bird habitat vegetation for many years. June 2003. Much of the vegetation is introduced and not good bird habitat (Casurina equisetijolia, Leucaena leucocephala [koa haole]).

Pluchea bushes on west end of island in old "Red Hat" area support hundreds of tropicbird nests. Extensive road surfaces in this area halted growth of vegetation. It will be many years before useful bird habitat vegetation can grow on these roads.

14


East Island showing flat, treeless habitat with thick grass. Jnne 2003. Used for nesting by brown boobies, masked boobies, sooty terns, and brown noddies primarily; all ground nesters. In the past, roosting by red-footed boobies and frigatebirds killed any bushes.

North Islaud, showing combination of flat sparse-grass habitat and some bushes. June 2003. B.ushes are being killed by nesting red-footed boobies and roosting frigatebirds. Lack of bushes probably limits the nesting population of both species. 15

Johnston Atoll Seabirds 2003 . Schreiber

Sand Island, east end. June 2003. Part ofthe original Johnston Atoll before dredging, with sand dune hill rising about 40 feet Grassy habitat is used by brown boobies, sooty terns, brown noddies aud frigatebirds for nesting (frigatebirds normally nest in bushes but on Johnston Atoll there are too few bushes).

Sand Island, west end. June 2003. Mostly grassy habitat Bushes were destroyed by nesting and roosting red-footed boobies and great frigatebirds causing the loss of 600-800 tropicbird nest sites. Buried building rubble is to the right. [6


OBJECTIVES The objectives of this study were to gather the necessary data on the birds breeding on Johnston Atoll in order to monitor the stability and health of the populations in conjunction with: 1) the construction and operation of the JACADS incinerator, potential leaks and smokestack emissions, 2) disturbance to the birds from the large increase in personnel using the islands of the Atoll, its waters and beaches, and 3) increased dumping of waste in the surrounding water.

The monitoring consisted of documenting and closely tracking any changes in the ecology, breeding biology and population sizes of the nesting seabird species. The study was designed to monitor all possible parameters in the birds that might be affected by JACADS, and to do the monitoring from year to year in a very consistent manner so that data were comparable among years. Since 1984 we documented breeding biology parameters ofthe birds, made comparisons of nesting success among years, and determined where and when any perturbation occurred to the population and its affects on the species involved. This long-term data base provides a very sensitive and effective monitoring system of the bird populations in relation to human activities on the Atoll. To study these parameters we gathered data on the breeding biology, ecology and survival of several species nesting on the Atoll and compared these data each year to our data from previous years, in addition to comparing them to data gathered on the same species elsewhere in the world. We have primarily studied the pelecaniform species since they: I) nest in small enough numbers to be very accurately monitored, 17


2) can be caught to be weighed and measured with minimal disturbance to the colony, and 3) can easily be recaptured to study nest site fidelity, recruitment rates, etc. Accurate monitoring of procellariiform (shearwater and petrel) and tern population sizes presents problems which make these species less desirable for a thorough monitoring program and particularly for the scope of this program: 1) some species nest in numbers too large to band and recapture so we do not know what individuals are doing and 2) adults of several ofthe species cannot be caught at a nest site so that we cannot tell what individuals are doing, what nest success for individuals pairs is, and how this may vary from year to year. We did estimate numbers of nesting birds ofthese species present on the Atoll during each visit. Fish and Wildlife Service personnel resident on the atoll made estimates of nesting numbers of some species in some years, but there is no consistent twenty-year record as different refuge managers pursued different objectives. The data gathered on the pelecaniform species (to a lesser extent on frigatebirds that nest in small numbers) ~ere as follows: 1) estimates of the total number of birds using the AtolL 2) numbers of breeding birds. 3) numbers of roosting birds. 4) estimate of number of nests receiving an egg. 5) estimate of number of young raised to fledgling age. 6) growth rates of young of red-tailed tropicbirds were measured annually (1984-2000). 7) rates and causes of mortality of young. 8) effects of human disturbance: actual destruction of nest sites, disturbance of nesting areas by human disturbance, etc. 18


9) monitoring of several parameters for red-tailed tropicbirds in two sites, one downwind of the incinerator and an upwind area or control site for comparison. Parameters measured are adult survival, fledging success, adult mass, egg mass and size, and recruitment rates of young. The information collected in this study from 1984 through 2003 provided the data necessary to monitor for any effects of the JACADS project on the birds on the Atoll. These data were gathered during two to three visits to the Atoll each year.

,

METHODS On each of our visits during the year we estimated total populations of each species of bird present, roosting and nesting. Estimates of population sizes for all species are summarized in Table IS for 2003. The previous pages of Table I are estimates of the previous years population sizes for comparison. Data on numbers of procellariiformes and terns are included in the table where available, but these populations are not as closely monitored and population estimates may only be within 10-20%. However, they constitute a good indication of the trends in those populations over the years. For three of the pelecaniform species (red-tailed tropicbirds, brown boobies, and red-footed boobies) we put a semi-permanent nest marker (Schreiber & Schreiber 1986) at a sample of nest sites. This enabled us to associate an individual pair of birds with the nest site and to do growth measurements on chicks too young to band. These markers were left in place from year to year. The markers were used to track individual birds and we kept enough nests marked to have an adequate sample size for studies of nest site fidelity, mate fidelity and chick growth. On Sand Island, at least 200 tropicbird nests were marked each year from 1984 through 19


1999. Beginning in 2000, red-footed boobies had caused so much damage to nesting bushes, that most tropicbirds abandoned nesting attempts there. On Johnston, we originally marked a series of nests along the north side of the runway (over 250 nests were marked from the Lanai west to the Theater) but this area of vegetation was removed during 1998-99. During 1998-99 other nests were marked so that pairs could be followed as needed: in the area of the ball field, around the MET Station and east of the Air Terminal. A series of nests downwind of the plant was also marked and followed each year. About 250 brown booby nests on the east end of Sand Island were marked. Red-footed boobies change nest sites after a few years and it is difficult to mark an area that can be followed from year to year. We keep about 100 marked nests on Sand Island each year and about 20-30 on East Island. During 1984 and early 1985 we marked all nests of all pelecaniform species using the Atoll. This soon became impossible with the population increase, and unnecessary for a statistical sample size. All nests of boobies and tropicbirds are visited at least once during each research visit to the Atoll and many are checked 2-3 times during a visit. We attempt to recapture as many banded adults as possible each year and to band all unbanded adults to monitor adult survival on the Atoll. At all nests of tropicbirds and boobies (marked and unmarked nests) we attempt to capture both adults and the chick:, banding them with an individually numbered aluminum Fish and Wildlife Service band. Growth increments were measured on red-tailed tropicbirds from 1984 through 2000. From 1984 through 1987, we measured growth of red-footed booby, brown booby, sooty tern, and great frigatebirds chicks to establish a baseline for future comparison as needed. Red-tailed tropicbirds are the only species to nest in any numbers downwind of the JACADS incinerator and were the species most likely to incur perturbations owing to the incinerator, thus growth studies emphasized 20


this species with measurements taken from 1984 through 2000. Chick growth and fledging success are two ways to assess the health of chicks. The extended season of red-tailed tropicbirds also allowed for seasonal comparisons (Table 4). Data on growth and development of nestlings were plotted in Figs. 19-30: culmen on mass, wing on mass and culmen on wing for each of the species on which we have done growth measurements. In order to obtain a growth rate, two to three sets of measurements of chicks are made (wing and mass), each 4 to 7 days apart (Ricklefs 1968, 1972, 1976, Schreiber and Schreiber 1989). From 1984 through 1989 we censused shearwater and petrel species, which nest in burrows in the ground and mainly on Sand Island, determining phenology and population size for each species. In subsequent years, we sampled the population and made estimates of the size of each.

Wedge-tailed shearwater adult near entrance to the burrow it is digging on Sand Island. They lay one egg and both adults care for the egg and young. 21


On Sand Island we erected a semi-pennanent grid of 100 meter square plots with PVC pipe on the west side of the east end of the island. This area was used to census the burrows for wedgetailed shearwater occupancy rates. FWS monitored Bulwer's petrel, wedge-tailed shearwater and tern population sizes in some years and those data may be obtained from them. We have concentrated our studies on the pelecanifonn species, and mainly give annual general estimates of population size for the procellariifonn and terns species. However, this report will continue to discuss and make recommendations for the preservation of all species on the atoll.

RESULTS AND DISCUSSION A summary of the historical and current population sizes of all breeding species on the Atoll is presented in Table 1. Detailed discussions of each species' population size, annual nesting success and other results are presented in the individual species accounts. Data on historic and current locations of breeding populations on the Atoll, by species and island are presented in Table 2. Egg size and mass data are presented in Table 3. In Tables 4 through 9 we give the results of our growth analyses over the years with results of analysis of variance tests comparing growth between years (Ricklefs 1976). These data are discussed for each species under the individual species accounts. Table 10 contains the results of the heavy metals tests on feathers, and Table II illustrates the delayed nesting season in 1991. Table 12 gives the annual mean mass (g) of adult red-tailed tropicbirds, red-footed boobies, brown boobies (by sex), white terns and sooty terns. Figures 1 - 13 are maps of the islands of the Atoll with breeding locations noted or described for each species. Figures 14-18 are the results of a vegetation survey to detennine what nest site characteristics are important to several species of nesting birds on the Atoll. These data 22

lolmston Atoll Seabirds 2003 - Schreiber

are discussed under the individual species accounts for the species involved. Figures 19 through 30 are plots of chick growth for red-tailed tropicbirds, red-footed boobies, brown boobies, great frigatebirds, brown noddies, and sooty terns. Plotted are culmen on weight, wing on weight and culmen on wing. These plots establish a baseline that can be used to compare growth parameters in future years. Figure 31 illustrates the growth in the number of nesting red-tailed tropicbirds each year since 1984. Figures 32-34 represent annual population counts ofthe number of nesting pairs of brown boobies, red-footed boobies and brown noddies. Appendix A gives recommendations made for base andJACADS closure procedures that would benefit seabirds and ensure their continued survival and high population sizes on Johnston Atoll. As final closure approaches, few of these recommendations were followed since FWS personnel wanted the island left in an 'attractive state' rather than in a state which would most benefit the continued status ofthe bird populations. Our estimates of the future of Johnston Atoll bird populations will be discussed it he section called CONCLUSIONS. Appendix B presents an analysis of survival, movements rates and nest success of red-tailed tropicbirds nesting downwind of the JACADS incinerator in comparison to the other birds nesting on Johnston Island (upwind of the incinerator; Schreiber et aL 2001; Journal of Wildlife Management paper). Appendix C is a pre-publication copy of a scientific paper that will appear in Oikos Journal in 2004 (Doherty and Schreiber et al.). This is a detailed analysis of juvenile red-tailed tropicbird survival to reproductive age, and of adult survival on Johnston Atoll. This is one of the only seabird species in the world on which we have enough data to detennine juvenile survival to reproductive age. 23


Counts. Counts of roosting birds (pelecaniforms) are given as a range because this number varies from day to day, with more birds roosting on windless days (Schreiber & Chovan, 1986). Counts of roosting birds are noted separately since most of these birds do not breed on this atoll. Most sea birds do not come to roost every night so that anyone count of a roost grossly underestimates the total population using the Atoll. None of the birds using this Atoll need to roost every night. They often stay in the air for several days at a time. From recaptures of the very few banded roosting birds we know some of the roosting birds come from the northern Hawaiian Islands. Dnring a visit we make 3 to 5 counts of roosting birds present for each species since there can be great day to day variation. There is no accurate way to extrapolate these counts to the actual number of birds using the Atoll since we cannot catch, band and recapture roosting birds. However, our counts are made in a similar manner each time to provide accurate year to year comparisons. Without banding and recapturing individuals there is no way to know if the roosting birds present on one day are the same birds present the next day or whether they represent an additional cohort. . By the end of 1988 we had banded 783 white terns on the Atoll. Yet when netting birds we found only 1 in 5 banded. These recapture statistics indicate that a minimum total population of around 3000 birds use the Atoll, allowing for some mortality over the three year period. Yet, only 40 to 100 birds were present on the Atoll at any given time during 1988. Harrington (1974) found a similar situation with the sooty terns on Johnston Atoll. Through banding studies he estimated 600,000 adults using the island in one season. However, there were only 130,000 nests present, which accounts for only 260,000 adults. The remainder of the population of these terns was thought to be juveniles that are not yet nesting, and adults that are learning how to go about finding a mate and nesting. 24


Pair of white Terns on Johnston Island.

Our estimates of the nesting pelecaniform, black noddy (Anous tenuirostris), white tern

(Gygis alba), and gray-backed tern (Sterna lunata) populations are the most accurate since essentially all nesting adults and young can be counted on each visit, and our visits are timed to not miss any successful nests between visits. Table I summarizes the historical and current population estimates for the breeding birds of Johnston Atoll, and estimated nesting success for pelecaniform species.

Potential JACADS effects on birds. There were 3 potential effects on the bird populations from the JACADS operation: I) birds nesting downwind of the incinerator may have been affected by leaks or stack emiSSIOns.

25


2) human disturbance to the birds owing to the increased human population. 3) birds being affected by increased ocean dumping of waste materials. All three of these had the potential to adversely affect tropicbird reproduction and survival. Our monitoring program was designed to determine if there was any adverse affect occurring to the birds . .We monitored tropicbird nests downwind ofthe JACADS incinerator and in a control site upwind of the plant (tropicbirds being the only species that nests in any numbers downwind of the plant). The downwind monitoring has taken place in the Red Hat area and Scientific Row. These two areas receive outfall from the stack emissions (some heavy metals: see Schreiber et al. 2001) and have high human activity connected with plant operations. The Red Hat area is defmed as all the area from the JACADS plant to the west end of the island, and all the area to the south and west of the Scientific Row bunkers. Scientific Row is defined as the area between the runway and the bunkers on the south side of the Scientific Row buildings, stretching from the west side of the JACADS incinerator, west to the end of the runway. Birds nesting in the HO site (northwest comer of Johnston Island) were also in the downwind plume of the incinerator smokestack. From 1992 through 2000 FWS personnel monitored nest success of birds in a downwind area (Red Hat) by checking nests every 44-50 days, more often than we were able to do visiting the Atoll between 2 and 3 times per year. Their estimate of nest success was similar to ours in each year, and their results also show no effect from the JACADS plant (Schreiber et al. 2001). Their nest success monitoring stopped in 2000. Human destruction of nest sites has been the greatest affect on the nesting birds of Johnston Atoll that is related to JACADS (see discussion under the species account for Red-tailed Tropicbirds below). Red-tailed tropicbirds appear to be able to tolerate a large amount of human 26


disturbance as they nest in close proximity to human activities on Johnston Is. From 1984 through 1998 we maintained a series of marked nests in areas on Johnston which are disturbed daily by human activity and found no difference in reproductive success, nest site fidelity or recruitment rates of these birds compared to a control area on Sand Is. where nests are essentially undisturbed by humans by daily activities of humans. This area was cleared of vegetation (along the runway) in 1998. There is no evidence that increased dumping of waste into local waters has affected nesting success in any of the species on Johnston Atoll. Adult birds would most likely be affected during the nesting season when they feed closer to the Atoll (still out of sight of land) than in the nonnesting season when they tend to disperse more broadly at sea. The generally high nest success of species nesting on Johnston and the increasing population size of most species indicate that they were not undergoing any perturbations, either man caused or otherwise.

Reproductive Success and Survival of Tropicbirds in Relation to JACADS. Reproductive success and survivorship are two of the basic demographic parameters (end points) that are monitored for any bird population to determine health of the population. While there are good estimates for reproductive success in many seabird species, estimates of survival rates are few (see Appendix B in Schreiber and Burger 2001), mainly since gathering the data requires many years of work in remote places. Our years of research on Johnston Atoll, Central Pacific Ocean allows us to examine survivorship in red-tailed tropicbirds for the first time. We compared reproductive success and estimated survival and movement rates, using modem mark-recapture survivorship analysis techniques (Clobert et al. 1994) for tropicbirds nesting in areas located both upwind and downwind of the JACADS incinerator on Johnston Island. We were interested in 27


movement rates to determine if birds were moving away from the downwind area for some reason. The methods and details ofthe statistical analyses are described in Appendix B at the end of this report (Schreiber et al. 2001).

Adult red-tailed tropicbird with 5 week old chick. Adults spend only about 1 hour a day with a chick this age and spend about 5 minutes a day with older chicks.

Juvenile survival rates are difficult to analyze and models have only recently been developed that can deal with the variables. Juvenile seabirds commonly take four to six years to mature and return to the nesting area to breed. But some also may return at one to seven years of age (young birds stay at sea for up to 6 years before returning to breed; Schreiber and Schreiber 1993). Some may emigrate to nest on other islands (still surviving) but their absence at the home island would be considered a death or non-survival. This delayed breeding and the fact that birds first return to breed at varying ages (age-specific breeding probability) complicates the estimation of juvenile survival (Clobert et al. 1994, Williams et al. 2002). There are no previous data on juvenile survival

28


and age-specific breeding probabilities for this species (or most seabird species: Schreiber and burger 200 I). Juvenile survival and age-specific breeding probabilities are of particular interest on Johnston Atoll because of the potential for negative effects on chicks surviving to breed during the JACADS operation. For instance, inhalation of heavy metals emissions from the smoke-stack of the JACADS plant could affect juvenile survival (see Schreiber et al. 2001, Table 7, for list of these emissions). Recent developments in model structures to estimate juvenile and adult survival, as well as age-specific breeding probabilities while taking detection probabilities into account, allow us to test the predictions that juvenile survival and age-specific breeding probabilities are negatively affected in the area adjoining the JACADS plant. We also examine adult survival in the three years postburning of the nerve gas (200 I - 2003) and compare that to survival during the incineration process. From 1983 through 2003, approximately 35,000 tropicbirds were banded. Banding locations on the Atoll by island and ages of birds banded were recorded (adult or chick). Approximately 45% (0.02 SE) of nesting adults are recaptured each year. Within Johnston Atoll there is an average probability of movement from one island to another between consecutive breeding seasons equaling 0.0079 'if 0.0002 (SE). This is a very small rate of movement, illustrating their exceptional philopatry to their chosen nest site. All comparisons are made between the set of birds nesting downwind near the nerve gas incinerator and those nesting upwind, away from any potential effects ofthe incinerator. As in our previous analysis (Schreiber et al. 2001) we used a multi-strata capture-markrecapture approach (Amason 1972, 1973, Williams et al. 2002) as available in program MARK (White and Burnham 1999). In Schreiber et al. (200 I) we used this approach to estimate recapture 29


probabilities (probability that a bird is caught and its' band read in anyone year), adult survival probabilities and movement probabilities between different areas of Johnston Island. Modeling transition (movement) rates between different areas or transition rates from nonbreeding to breeding status can be done in an analyticaUy similar way. However when transitions between breeding status and area are taking place at the same time and when nonbreeders are not detectable (birds stay out at sea until mature), then these two transition rates are confounded. Since, in our previous modeling, we found no significant differences· in adult movement rates (between upwind and downwind areas) and since these rates were very smaU, we decided to assume that juvenile movement rates would have a similar pattern. This assumption affects how both juvenile survival and age-specific breeding probabilities (at what age a bird returns to breed) are interpreted. Essentially, this same approach was used by Spendelow et al. (2002) to estimate post fledging survival and age-specific breeding probabilities in roseate terns (Sterna dougallii). Assumptions required by this model are similar to those required by Cormack-Jolly-Seber (CJS) models (Cormack, 1964, Jolly 1965, Seber 1965), (I) recapture and transition probabilities are the. same for all marked birds found in a particular state and sampling period; (2) birds behave independently with respect to survival, recapture and transition probabilities; (3) bands are not lost; (4) all samples are instantaneous; and (5) state transition probabilities reflect a first order Markov process in the sense that the state of an animal at time t +1 is stochasticaUy determined as a function of its' state at time t. (Williams et al. 2002). We believe that our study and the study species are an ideal candidate for this type of modeling because we meet these assumptions well. Red-tailed tropicbirds do not flock and are thought to behave independently except during the breeding season. Although this species lives long enough to have bands wear and fall off, the population was followed very closely (approximately 45% of breeding adults recaptured each year), 30


and worn bands replaced regnlarly. We also restricted onr sampling to the breeding season, while not instantaneous, it is a period in which high mortality (a dead adult is rarely found) or movement does not occur. We performed a goodness of fit test on our most general model and, to help correct for any over dispersion in onr data, we also estimated an over dispersion factor ( c) to adjust estimates and statistics. Goodness of fit tests and

cwere based on the Pearson goodness-of-fit test

in which all groups with expected values less than 2 were pooled.

Model Set We constructed models including adult survival ( rpA ), juvenile survival (defined as survival from fledging until the age 1; rpJ), recapture probability (p ), and age-specific-breeding (or transition) probabilities (age = 1 to 5;

'l/age)

were modeled as functions oftime (t) and site (upwind

or downwind of the JACADS site). Due to the tropicbirds propensity to stay out at sea for up to 6 years after fledging, we were only able to estimate juvenile survival rates meaningfully for the first five years of onr data set. By definition, there is no recaptnre rate for juveniles (when a bird is recaught for the first time it is a breeding adult). Thus onr most general model was designated as A J age bmd" tpsite*trpsite*IPsite~I'f/site'f/sjte*t •

0 ur pred·· . fioeused on tee h f"lects 0 f· lctions 0f Interest Site. W e thus

constructed reduced models in which the effect of site was removed for each parameter independently, as well as for both of the survival rates together. These models were designated A

CPt

J CfJsite*t

as

age breeder fi . 1 b elng . cons tant over 81·te, cP site*/P A J age breeder c: Pslte*tfJ/site 'f/sile*t or aduIt survlva J_or t P site*t'f/site 'f/site*t

juvenile survival being constant over site, rp,A rp: p,"e>' '1/;;: '1/:;::;" for both adult and juvenile survival being constant over site,

rp;">,rp;,,,>,p,'I/:ff:'I/:;::;" for recapture probabilities to be constant over site, 31


A

J

age

A

J

age

({Jsite.,({Js'''',Psite'''I/

. and Lor age-spec!·fiIC breed·mg prob ab·l·· Iitles b· emg constant over Site,

b",d" +:

'l/s'"''

. constant over site. . Lor breed·mg d·Ispersa1rates b emg

b",d" "

({Jsite"({Jsite"P site"'l/site '1/,

Since we found no difference in adult movement rates between the two sites in our previous analysis (Schreiber et al. 2001) we also ran a set of models in which we did allow adult movement rates to vary across sites. We used Akaike's Information Criteria (AIC; Burnham and Anderson 1998) to compare the fit ofthese models. We specifically used the small sample approximation and

c adjusted form of AIC denoted as QAIC

c

(Burnham and Anderson 1998) and considered models

with QAICc values differing by less than 2 to be equivalent. We also calculated AlC weights for each model to help us interpret the relative strengths of each model (Burnham and Anderson 1998). This allowed us to calculate model-averaged estimates. A modeled average estimate is essentially a weighted average based on an individual models weight. This allows inference to the entire model set. Such a model-averaging approach is likely superior to relying on parameter estimates from a single model (Burnham and Anderson 1998). All results present in the figures are modeled averaged estimates with their associated 95% confidence intervals.

Results.

We followed 35,000 birds banded as juveniles and adults over 12 years of data collection (1992-2003). Reproductive success. To test for differences in reproductive success we used a one-sample

t-test on the yearly differences in reproductive success (number fledged/number eggs) in upwinddownwind areas. By examining the difference in reproductive success we control for year and overall island effects and focus on the difference between the two areas.

32


There was no significant difference in reproductive success (chicks fledged from eggs laid: 68 85% annually, Fig. A) between the upwind and downwind areas (T = 0.00, P

=

1.00; Fig. A)

throughout plant operations. Annual reproductive success varied little between the two areas, decreasing primarily in El Nino years (Schreiber and Schreiber 1993, Schreiber 1999). Annual variation in reproductive success was attributed to the occurrence of El Nino events when hatching success and fledging success both declined (Schreiber 1993, 1999). There have been no unexplained die-offs of birds on the Atoll and the occurrence of EI Nino Events is the only factor that has lowered nesting success.

Figure A I/)

1.0

B 0.9 o 0.8

iil

0.7 ~ 0.6 tl 0.5 :::I

0.4

-c 0.3 Q, 0.2 ~ 0.1 0.0

e

"6--.....-~ ~·~Upwind

- ..::. - Downwind

+--.,.....--.---..,.----,r---,.---.--.....

1992 1993 1994 1995 1996 1997 1998 1999 Year

Figure A. Mean reproductive success (number fledged/number eggs) for nests upwind and downwind ofthe JACADS incinerator during incineration.

Recapture Rates. A summary of overall capture histories is shown in Table A. As in our previous analysis (Schreiber et al. 2001), in which we used a different approach to goodness-of-fit testing, our goodness of fit test failed (P < 0.01), which indicated that our data were over

33


c= 2.06, which was more

dispersed. To correct for this over dispersion we incorporated a

conservative, in the sense that we inflated our variance more than with our previous estimate of 1.6. Overall the model that ranked highest by QAIC, coded for temporal variation in adult survival, juvenile survival, probability of recapture, adult movement rates, variation across sites for detection probability, and both age-specific and first-time breeding probabilities (Table B). None of the other models described the data well with QAIC, > 3. The only other model that had much

Table A. The likelihood, number of parameters, and AlC rankings of each model. We used the small sample approximation and adjusted AlC using c as denoted by the QAIC, term. !'J.QAIC, is the relative difference of each model from the best fit model (lowest QAICc ). The !'J.QAIC, weight is the relative weight of evidence for each model. Adult survival (rpA), juvenile survival (defrned as survival from banding until age 1; rpJ), recapture probability (p ), age-specific natal dispersal probabilities (age = 1 to 5; 'lf age ), and breeding dispersal rates ( 'lfb",d,,) were modeled as functions of time (t) and site (upwind or downwind of the JACADS plant).

!'J.QAIC, QAIC,

Model A

J

tpt lPt

age

Psite*zlf/site 'f/site*t

A J tpsile*ttpl

Psite*tlf/site If/sUe"t

age

age

J

A

age

J

age

J

age

A

J

age

parameters

43397.49

0.00

1.00

1.00

85.00

43417.13

19.64

0.00

0.00

96.00

43417.48

19.99

0.00

0.00

97.00

43433.45

35.96

0.00

0.00

107.00

43447.74

50.26

0.00

0.00

96.00

43574.46

176.97

0.00

0.00

96.00

43816.14

418.66

0.00

0.00

97.00

breeder

breeder

breeder

tp site,,/Psite*' P ('If site I.f/site"!

rp site*ttpsite*t P site*,1f/

Likelihood

breeder

0.6 .~ 0.5 :::I III 0.4 .... :::I 0.3 '"0 « 0.2 0.1 0.0

Upwind --B--- Downwind

----tr-

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 Year

Figure C. Adult survival rate for birds upwind (squares and solid line) and downwind (triangles and dotted line) of the JACADS plant from 1992 to 2001. Model-averaged means and 95% confidence intervals are shown 38


Upwind Year

Downwind

CPt

'A

SE

CPt

'A

SE

1992

0.87

0.02

0.87

0.02

1993

0.83

0.02

0.83

0.02

1994

0.89

0.02

0.89

0.02

1995

0.85

0.02

0.85

0.02

1996

0.92

0.02

0.92

0.02

1997

0.92

0.02

0.92

0.02

1998

0.82

0.02

0.82

0.02

1999

0.82

0.03

0.82

0.03

2000

0.81

0.03

0.81

0.03

2001

0.87

0.04

0.87

0.04

x

0.86

0.86

SE

0.04

0.04

(ttot+1)

Table D. A comparison of adult survival rate for birds upwind and downwind ofthe JACADS plant from 1992 to 200 I.

Juvenile Survival Rate. Since juveniles can take 6 years (longer in some cases) to return to

breed, we did not estimate juvenile survival for the most recent 5 years (many birds from those cohorts would not have returned yet). Over the first five years we did not find any differences in juvenile survival rate for tropicbirds upwind (x = 0.71 survival, SE = 0.03) as compared to downwind (x =0.71, SE = 0.03) of the JACADS (Table E, Fig D).

39


Upwind Year

Downwind

/PI

'J

sF;

/PI

'J

sF;

1992

0.75

0.04

0.75

0.04

1993

0.75

0.04

0.75

0.04

1994

0.73

0.04

0.73

0.04

1995

0.69

0.04

0.69

0.04

1996

0.75

0.05

0.75

0.05

1997

0.95

0.06

0.95

0.06

x

0.77

0.77

sF;

0.09

0.09

(t to t+1)

Table. E. A comparison of juvenile survival rates for birds upwind s and downwind of the JACADS plant from 1992 to 1997.

Q)

'Iii ...

ca> .~

:l fIl

.!!! r::: Q)

.,:l>

1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0

Upwind --8-- Downwind &

1992 1993 1994 1995 1996 1997 Year

Figure D. Juvenile survival rate for birds upwind (triangles and solid line) and downwind (squares and dotted line) of the JACADS plant from 1992 to 1997. Model-averaged means and 95% confidence intervals are shown. (High juvenile survival for 1997 is an artifact of the model and does not represent a true estimate, see Doherty et al. 2003.) 40


Age-specific First-time Breeding Probabilities. We did not find any difference in age-

specific breeding probabilities for birds breeding upwind and downwind of the JACADS plant respectively: age I

(x = 0.03 SE < 0.00, x = 0.03 SE =

x =0.02SE =

0.01), age 3 (x = 0.29

SE =

x = 0.58 SE =

0.05), or age 5 (x = 0.53

0.01), age 2 (x = 0.02

x =0.29 SE =

O.oz,

SE =

O.oI,

0.02),.age 4 (x =0.58

SE = 0.04,

SE = O.ll, x = 0.52 SE = 0.12: Fig. E). This indicates that

birds return to breed at the same age in both areas. If there were a delay in the return of chicks as adult birds in those raised in a downwind area it could indicate some impairment of behavioral development, such as a delay in the development of courtship behaviors. For both upwind and downwind sites the rate at which birds recruited into the breeding population increased with age. There was no difference between the two areas, reflecting that there was no effect of being raised in proximity to the JACADS plant.

==

'" 1.0 .c 09 . ~ 0.8

e 0.7

o Upwind ~Downwind

Co

g> 0.6 'U '" 0.5 ~ .c 0.4 u

!E 0.3 u

:i

"'ci>

Cl

«

0.2

0.1 0.0 -J-1::='--~~-'--.~ 2 3 1

4

5

Age

Figure E. Age-specific breeding probabilities for tropicbirds age 1-5 for sites upwind (clear bars) and downwind (hatched bars) of the JACADS. (Means and 95% confidence intervals are shown.)

41


Age-specific Dispersal Probabilities. We found differences in the philopatry and emigration rates of birds fledged upwind and downwind of the JACADS. For all ages at which birds recruited to breeding status, birds that fledged from upwind sites showed greater philopatry and were less likely to first breed elsewhere than were birds that fledged downwind (Figure F, Table F).

1.0 0.9 "Iii .2l 0.8 ~ E 0.7 !E CQ 0.6 o !/j 0.5 Q)'" Co Q) o. 4 '{I g- 0.3 Q)'-02 til 'C . '"

0\

..."

IS· '\

o~.o~ M

l'>~'; \..Y

.:\} ~e';"'·

Figure 4a. Red-tailed Tropicbird nesting sites on Johnston Island, .Birds nest under bushes and trees scattered throughout the island,

tN SAND

ISLAND~

JOHNSTON ATOll l
.".r;;;,~s''!>'/,'

fr~o z

w ::>

o

w

,..-

~

.... ....

~

...

I

w

I

Q..

50

/ /

/

10

e:( -A

I I

IJ..

.... ....

~

..

::::>

/

~

/

::::>

()

;!

'" 1/

/

1

> l-

Ilrandom

/

a:

W

2

3

4'

5

6

DISTANCE NEAREST NEIGHBOR

7

Figure 17. Nearest neighbor distances {in meters) for actual Red-footed Booby nests compared to

a random set. 19B4.

,..~

,..,....... ",-""'--- - ------

random

100

--------------::,..:> i

./

./

.....

./

(

Z

I

ill

I

()

I

a:

I I

>-

30

ill CL

I I

ill

I

50 >

()

l-

Z ill

:::>

e:( -.J

actual

20

o

:::>

rr:

:::>

~

ill

I..!..

()

10

10

20

30

40

DISTANCE TO NEAREST NEIGHBOR

FREQUENCY 20

10

1000

-z

- 800

:::;E ....... I--

I--

u..

~

...."

....'"::> '"I!!... '" '" E 0

600 >I--

0

0

...J

W

I--

400

-0

>

0 ...J w

200

>

.5 1.0

2.0

HEIGHT Figure 18. Wind velocity (ft./min.) recorded at actual and random nest sites

for Red-footed Boobies compared to height of nests (meters). 1984.

BROWN BOOBY CHICKS. ~OHNSTON ATOLL. 1983-1987 PLOT Of GROWTH MEASUREMENTS PLOT Of WING'CULMEN

LEGEND: A • 1 OBS. B • 2 OBS. ETC.

I

450 ... A AAA.

S B ABAA BAAS A AACAE AC

A

400 +

AA B

AA 0 AACe A BAOD DA BAA

o BAAS AAAAA

BCAB AC A CADB EBB ACUBCB AB A

350 ...

A

AA

A

A ABBAAC CoA AA A BAA CA AAAAA W 300 ... i

A B

.

G

AA ABA BA A B

250 +

l

C

A A.A... eo A AA A A AAS AA B SA BBA B AA BC A AU B B

A

E

US A A A

A

ABAB B

N

G

A

A

A

A A A

T H 200 ...

A

M

A

AA B

AA

ABB

A

A

A

AA A BAA

B

A A A A

M 150 +

A

A

A A

A

BAA

A A ADA AB

'00 •

CAA

A BAASA

A BCCACB B A AECCEAOAAA 50 •

I)

I

C BeG OA

~A

A

A

"A.lACAB A

A

SA

ACBBEf. DBB A IIFBBCCFDGADCABB AFDOlle_FBDS. A

A

.,

-----~--~---~--~-+-~--~----+----+----+----+----+----+- ---+----+----+----+----+----+----+----+----+----+----+-----------.-----~3 1$ 23 ,2$ 33 38 43 48 53 58 ( 6 3 68 73 78 83 88 93 98 103

CULMEN LENGTH

MM

Fiqure 19. Brown Booby Chicks. Plot of wing length on culmen length, 1983-1987.

BROWN BOOBV CHICKS.

ATOLL.

~O~WSTON

1983-1987

PLOT Of GROWTH MEASUREMENTS PLOT Of CULMEN-WT

LEGEND: A • 1

~OS.

B • 2

~OS.

ETC.

I

110 +

I

A A lAAe AA A A AAAAB. AB AE OBCCB 0 A ••• CAO OOAAACEC EO AOBAA ABABACDBAGEEBAB CAABAOB ACBAABA AAACAC lOCK GOlBA... BBBA SA A A AB BAA EAOOABA BAAA A A AA A

100 +

I

A

go.

c

80

u L

A A

I

A

E L

60

E

N G T

+

A A

I I

AS AA.A A

BB

A.A",

Be

A

A A

A A

A

"

A A

• A

A

C

A A AA

UB AAAS

ABA

A

A AA A A A

+

A

A

A A B

AA'" 8AAAAB 8A OA"''''

DB EBA AB AA AA A A AA BA A B AAAABA BBAee A A A A .I.e ..... A8

A

B

B

A

M '0 •

B A

ABB BADG AD AA AfBD

30 •

I

I

AB

BAA

A

I I I

".

B AA

B

A A

AA A A A

SO,

H

8

A

M 70 • N

AA A CBAAAB BOA

B ABA

FB

20 •

cea PG AM A

'0 •

"Ojco~ "Ojco "OjcoOj "OjOj" " OjOjf'1:> "OjOj~ "OjOjco "OjOjco1-~~~1-~~1-1-~F)~

i

YEAR

Figure 3l. Number of nesting pairs of red-tailed tropicbirds by year.

600

VI

.... "C

m

...0

300 [Ill Banded

(lJ

.c

asChicksBBanded as Adults I

E :::l

Z

100

o 2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

Age Figure 32. Age of adult red-tailed tropicbirds recaptured on Johnston Atoll during 1998. Birds banded as adults are of unknown age but are listed at a minimum age.

17

18

677

50

t,.;:-:.»»>?llib!i

f::'.&mMm

AI!I!I!IOIII

oo~

W"""N'"""-"-_

11'lt:

"/"Y»"':'''':D>O>

~

"0

.... Q)

....

Number of Chicks Banded during that Year

-

40

::::s 0..

ro

U

Q)

0::

....t:

30

Q)

U

.... c.. Q)

20

10

o 1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

Year Banded Figure 33. Red-tailed Tropicbird. Percent of each cohort year recaptured through 1998.

1995

1996

en ..... en 400 0) Z '+-

0

I-

.0) ..Q

E ::J

z

200

o

,,OJ9:J':J ,,OJ9:J~ ,,OJ9:J1. ,,OJ9:JOJ ,,OJOJ'' ,,OJOJ':J ,,OJOJ(() "OjOj9:J 't'0'0'0 't'0'0't't'0'0~

YEAR

Figure 34. Number of brown booby nests by year.

.... C/) C/)

Q)

1000

Z '+-

0

I,;..

Q)

..0

E

::J

z

500

o

tx CO \9Jco':J \9JCO~ \9JC01 \9Jco9J \9J9J\ \9J9J':J \9J9J((:; \9J9J tt\J\J\J tt\J\J'J,. tt\J\J

YEAR

Figure 35. Number of red-footed booby nests by year.

12000 (J) .......

10000

(J)

(J.)

z

'+-

8000

0

L..

(J.) ..Q

E

6000

:::J

Z

4000 2000

o

,,OJco0;) ,,OJco~ ,,OJco"\ ,,OJcoOJ "OjOj" ,,OJOJ0;) "OjOj((:) "OjOjco tt101010 tt1010'ttt1010~

YEAR

Figure 36. Number of brown noddy nests by year.

Johnston 2001 Seabird Report - Schreiber

APPENDIX A

Johnston 200 I Seabird Report, Appendix A - Schreiber

APPENDIX A In

Breeding Biology and Ecology of the Seabirds of Johnston Atoll, Central Pacific Ocean 2000

Johnston Atoll Closure: Suggestions to Enhance Bird Populations By: E. A. Schreiber, Ph.D. National Museum of Natural History, Smithsonian Institution 4109 Komes Ct., Alexandria, VA 22306 Phone 703 768-6726 [email protected]

Introduction. From 1983 through 2001 (19 years) I have been studying the seabird populations of Johnston Atoll. From my extensive experience on the Atoll, I would like to make some recommendations during the base closure process that would ensure the continued health of the bird populations, and may possibly be the only way to assure the survival of Red-tailed Tropicbirds nesting on the Atoll. My research on the Atoll was originally set up to monitor the birds prior to the JACADS incineration process (to establish baseline data) and throughout the incineration (in order to ensure the continued health of the birds). The major concerns about birds were I) direct effects on birds nesting downwind ofthe JACADS plant, 2) effects on the birds from the increased human population on the atoll and increased disturbance of nests, and 3) effects on the birds and their food source (fish and squid) from any contaminant source and fi'orn increased ocean dumping of waste. Now my major concern is the best way to leave the Atoll in a condition that will most benefit the bird populations. I have studied tropical seabird breeding biology and ecology for 30 years. The following suggestions are made after extensive experience with these birds in many colonies around the world, as well as after 18 years of detailed work on Johnston Atoll. None ofthe species nesting on Johnston are endangered, however, current populations of these birds in the Pacific basin are estimated to be 1-10% of what they were before extensive persecution by man (Pregill et al. 19944, Steadman 1989, 1995). Johnston provides an important nesting area where these species have been able to reproduce successfully without introduced predators. During the base closure process some steps could be taken that would help guarantee that the atoll remains an important nesting site for seabirds. The majority of problems that the seabirds have incurred over the past 18 years stem from destruction of nesting sites caused by the seabirds themselves. This damage will threaten the survival of Red-tailed Tropicbirds on the Atoll after man leaves, and could cause reduced nesting populations of Red-footed Boobies and Great Frigatebirds. With some, perhaps unexpected, measures this type of damage can be mitigated or prevented. These measures are discussed below. Thus far, we have documented essentially no effect to the birds from the incineration operation (8 biological end points measured: see Appendix B and main body of this rcpmt)o A

Johnston 2001 Seabird Report, Appendix A - Schreiber

small amount of bird habitat and some nesting sites have been lost since the incineration began (to a new rifle range, to clearing vegetation along the runway, etc.), but the incinerator and the incineration process have had no measurable effect on the birds nesting downwind of it. All the basic end points below, known to show effects of contaminants on birds (Fox et al. 1991; Burger and Gochfeld 2001), have been measured and no differences were found between birds nesting downwind of the plant and those nesting upwind (references listed below are those which state this is an appropriate end point to measure in monitoring for contaminants): 1) population size (Hoffman et al. 1990, Lipton et al. 1993, Burger 1995), 2) adult mass (Finley et al. 1976, Hoffman et al. 1990, Burger 1995, Furness and Camphuysen 1997), 3) egg mass (Finley and Stendelll978, Stoewsand et al. 1978, Burger 1993), 4) hatching success (Kendall et al. 1982, Clarkson et al. 1985, Burger 1993), 5) fledging success (Gochfeld and Burger 1988, Lewis and Furness 1991, Koster et a1. 1996, Work and Smith 1996, Furness and Camphuysen 1997), 6) presence oflesions or deformities on chicks (Fox et al. 1991, Burger 1995, Burger et al. 1992), 7) survival of adults from year to year and survival of chicks to breeding age (Finley et al. 1976, Hoffman et al. 1990, Burger 1995, Furness and Camphuysen 1997), and 8) chick growth (Heinz et al. 1989, Burger 1993, Burger 1995). Limited nesting habitat is currently probably limiting the number of nesting birds on the Atoll. Bushes, trees or other raised nesting habitat are needed by several species for nesting and are in short supply on Johnston Atoll. Since Johnston Atoll is mostly man-made, there are some unusual problems that need to be addressed. I am purposefully keeping this report short. If further information is desired I can provide it.

Preservation ofland mass. Maintaining a seawall of some sort will help preserve the landmass (mostly dredged up by the military) of the atoll so that it is available for nesting seabirds. Scrap concrete and concrete rubble could be used to reinforce the seawalled areas and non-seawalled areas of all the islands. In areas where the wall is deteriorating and erosion is occurring, concrete rubble could also be used to retain the soil.. The east end of Johnston, North and East Islands are in the greatest danger of eroding as this is where the current strikes the islands as it washes over the Atoll. I recommend placing as much concrete rubble, or biologically safe rubble, as possible along the top of the existing wall and in the water immediately adjacent to the existing wall, as well as in areas where there is no sea wall.

Nesting Habitat and the Need for Artificial Habitat Construction. There is a definite lack of nesting habitat on the atoll for those species that require trees or bushes, probably due to a lack of fresh water and nutrients. Also, the tree-nesting and roosting species (mainly Red-footed Boobies and Great Frigatebirds) congregate in dense groups and destroy habitat for themselves, as well as for Red-tailed Tropicbirds which need shade bushes under which to nest. The bushes are destroyed by excessive guano deposition and plucking of

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limbs for nesting material. In recent years tropicbirds have lost well over 600 nest sites to nesting and roosting boobies and frigates. Currently, Johnston Island provides the only nesting area for tropicbirds that is safe from destruction by the large tree nesting species. Once man is gone from the Atoll, I expect boobies and frigates to eventually nest and roost on Johnston Island, killing the majority of bushes and trees there. This will cause the loss of most tropicbird nesting sites on Johnston Island itself. The tropicbird population of the Atoll could easily be expected to go from 3,000 nests per year to 100 or fewer as more and more bushes are destroyed. This unique population of tropicbirds could eventually be extirpated from the atoll. Also, the limited number of bushes available for nesting probably limits the number of booby and frigate nests on the atoll. They do nest on the ground sometimes, but greatly prefer bushes. If all bushes are destroyed, many fewer ofthese two species will nest. In order to preserve nesting and roosting habitat, preserve the population of tropicbirds on the Atoll and increase the nesting numbers of boobies, frigatebirds and White Terns, I strongly recommend establishing some man-made nest sites. Seabirds readily use buildings and rubble for nesting sites on Johnston Atoll and on many other Atolls around the world. Well designed base closure plans could provide an increase in available nesting habitat and provide some "permanent" habitat that boobies and frigates cannot destroy. As cement block and concrete buildings are demolished, the rubble could be piled in appropriate areas for nesting habitat. Tropicbirds will nest in the shady crevices at the bottom (as they do now under rubble on the north side of the lay-down yards on Johnston Island). Red-footed Boobies, Frigatebirds and White Terns will readily nest on top of the rubble. Concrete will provide the most permanent habitat. Corrugated iron and wood deteriorate much faster. Base closure plans that incorporate some basic guidelines will ensure maximum use of the rubble and safety ofthe birds. The most used rubble piles currently consist of large pieces of rubble, stacked haphazardly to leave spaces open at the bottom. Piles should be between 3 andl2 feet high and should be fairly stable. Narrow strips of rubble from 5 to 20 feet wide (rather than one large pile) will provide more habitat for Tropicbirds who need to be able to crawl into a shady crevice from the edge. Size of the rubble pieces should allow them to stack, in some random fashion so that crevices are available on the ground level. Exact placement around the Atoll is probably not a significant factor. The different species of seabirds do choose various wind levels in which to nest (Schreiber 2000), for instance Brown Boobies prefer higher wind levels than do frigatebirds for nesting. But placement of rubble in various random areas will accommodate this. If the runway is to remain active, no rubble piles should be put within 100-125 feet of the runway. The aerial courtship of Tropic birds generally occurs over and near suitable nesting habitat and frequently ranges out 50-100 feet on either side ofthe potential nesting site.

Potential Entrapment of Birds in Man-made Structures. Three hazards can cause entrapment of birds: holes in the ground, buildings, and large metal or cement containers. These are fairly minimal hazards on Johnston and an insignificant number of birds have been affected by them in the past. From 1984 to 2001 we have found only about 15-20 birds entrapped (about lIyear). Johnston Island, once deserted by people, has multiple hazards that could pose an entrapment problem for a few birds if they are not properly prepared for desertion.

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Over the years man holes and other below ground access holes have caused a problem for a few birds that fell into them and could not get into flight to get out. Care should be taken to fill in or cover any narrow, deep access holes to below ground areas. Metal covers over holes have rusted away in a few places and I'm sure this would happen again if new covers are placed over the holes. The safest course of action would be to push debris into the holes. Holes only a foot or two deep are not a problem. Birds could walk out of a hole if there is ramp. Buildings in themselves do not cause an entrapment problem as long as birds can get out, either by walking or flying. Doors or windows that could flap open and closed should be removed. Sealed doors may last 10 to 20 years but could eventually pose a problem as they become unsealed. Windows should probably be removed as they will eventually break and birds will have access to the inside and possibly not be able to fly out. Birds may also not see the glass and fly into it, although glass could be painted on the inside to prevent this. Breaking out the glass may be all that needs to be done. Glass pieces lying on the floor of a building should not affect the birds, though it could pose a people hazard. When a bird flies into a building that has an inside ceiling higher than about 15 feet it may become entrapped simply because it may not known enough to fly down to get out the doorway. I am not sure this is true but several white terns have flown into the large gym building on Johnston and not left for a day or two. The birds were removed after that so we don't know if they eventually would have found a way out. We have done no experiments to determine if, with no human disturbance around, the birds might actually fly down and out the doorway on their own. Without any data to show whether they will or not, the safest course would be to make a hole in the roof or upper walls of high ceiling rooms in buildings (floor to ceiling height inside over 15 feet, with doorways only 7-8 feet high) so that birds can fly out. Birds probably will readily fly down 4-8 feet from the ceiling to exit a door, but distances over that may pose a problem. If it is desired to leave roofs in tact, a hole in the side of a wall large enough for a bird to fly out (say 8 by 8 feet) would suffice for an exit. Birds have excellent vision and will see the hole readily as long as it is in the room in which they are stuck. For multiple room buildings with high ceilings (over 15 ft.) I would recommend that a hole be made in each room or that interior walls be opened up to some extent. Once in a building birds can walk, so they may go from room to room. Any cement or metal containers large enough to hold a bird that are left should have openings on the side, or near the ground so that birds can get out, by walking or flying. We found one bird trapped in the bottom of 2 foot diameter cement tub 3 feet deep that it could not fly up and out of. The tub, turned on its side would have made a great Red-tailed Tropicbird nest site. It is not necessarily easy to detail a plan for making buildings "bird-safe" given the variety of buildings, holes and containers on Johnston Island. It may be, that part way through the closure process, I could make an inspection of the buildings thus far prepared and make recommendations for any further treatment, or any changes in treatment for other buildings. I could also do a walk-through of the buildings at any time and make suggestions for individual buildings if desired.

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Johnston 200 I Seabird Report, Appendix A - Scbreiber

Survival of Existiug Plauts. Lack of fresh water and huge amounts of guano deposition are a problem for the survival of plants (bird nesting habitat) on Johnston Atoll. Unfortunately it is a small island with tremendous numbers of birds trying to use it. I recommend leaving some cement pads and foundations around the islands because they drain rainfall to the sides and provide an increased water supply for the surrounding bushes. For example, on Sand Island the old barracks building and tennis court both used to provide a means to get extra water to the plants surrounding them (as does the current power plant building on Sand). When the barracks building and tennis court were removed, the surrounding plants died with the resultant loss of nesting habitat. On North Island, rainfall runoff from the existing large building provides increased rain water to the surrounding bushes and trees that provide good nesting sites for Red-footed Boobies. Without these buildings and cement pads, more bushes and trees will be lost, reducing the number of nesting boobies and tropicbirds and placing additional pressure on the remaining bushes. If buildings are demolished, the remaining cement pad could be left in place. It could be argued that removing the cement pads would open up more ground space for ground nesting terns, and this becomes a question of which species to manage for. I would suggest it is better to manage for increasing the population of tree nesting species (Red-footed Boobies and frigatebirds) and tropicbirds, given that the worldwide populations of the ground nesting tern species present on Johnston Atoll greatly exceed the worldwide populations of the tree nesting species and of tropicbirds.

Introduced Plant Species. Ideally, all introduced, invasive species of plants should be removed from the atoll as part of the closure process. This is probably not possible or practical, but some steps can be taken to ensure that adequate appropriate vegetation remains for the use of birds. Casurina (Ironwood: an introduced species) is an invasive species that is known to kill native plants as it spreads. It should all be removed and attempts made to reduce the seed load. It is not good bird habitat. The limbs are too weak to support White Tern and Black Noddy nests well. Many nests of both species are lost each year during storms owing to lack of needed support and stability. It is not good habitat for Tropicbirds, as it forms dense, tall forests that are difficult for the birds to get in to and out of. It has shallow roots and does not hold soil to prevent erosion. Currently White Terns, Black Noddies and tropicbirds do use the Casurinas for nesting, for lack ofbetler habitat. Nesting in Casurina is much less dense than in their natural habitat. All three generally nest in native bushes such as Scaevola and Tournefortia on other atolls. Both of these plants exist on Johnston currently, in small amounts. Pluchea, currently present in a substantial amount, is also used extensively by tropicbirds. It is not the best habitat for them. It is highly transient, dying back after only 3-5 years and causing the loss of nest sites to tropicbirds. Tropicbirds are exceptionally philopatric, returning to the same nest site and mate for many years in a row. They also depend on finding last years nest site to meet their mate. The loss of habitat, such as occurs when Pluchea dies back, causes these birds to lose their mate, and then lose one or morc breeding years while finding a new one, which some never find. Pluchea should not be planted. If Casurina trees are to be removed, other habitat should be planted nearby first; ideally at least 3 years before the Casurina are removed. The loss of the Casurina trees without replacing

5


the habitat ahead of time will cause the loss of production of many hundreds of chicks of tropicbirds, black noddies and white terns. Adults would have no place to nest for years until the newly planted vegetation grew large enough. Large sized, dead Casurina trees, lying on their side would provide roosting sites (and a few nesting sites) for Red-footed boobies and Great Frigatebirds for 10-20 years while other vegetation grew, but leaving these trunks might make it difficult to try to get rid of the seed load of Casurina. This should be considered. I recommend a program of immediately planting several hundred Scaevola and Tournefortia bushes (both good native nesting habitat on tropical coral atolls) around Johnston that could begin growing before the island is closed. The advice of a tropical botanist should be sought. Planting should be conducted by a professional that can advise on the best method to ensure the survival of the plants in this harsh climate and soil. Then, if desired by the Fish and Wildlife Service, all of the Casurinas could be cut down in an attempt to get eradicate the species from the Atoll. Ideally, Casurina would not be removed until other suitable habitat was available. Other non-native plant species could also be cut down, particularly invasive ones. All tree and bush stnmps should be treated so they won't re-grow. In areas where the ground is compacted and very hard, loosened soil would benefit plant growth. The roots of bushes and trees do not grow in compacted soil well and most transplanted or planted trees will die if the soil is not loosened sufficiently. Newly planted bushes may take 5-10 years to become good bird habitat, which makes immediate planting of alternative habitat a priority. If most of the existing bird habitat (bushes and trees) is destroyed in the clean-up and closure process, thousands of birds will lose their nesting habitat. Many of these birds will never nest again, as they search for a mate and a new nest site. Basically, hundreds of adult birds will be removed frO)ll the breeding population, as though they were killed. Keeping as much current habitat as possible will do a lot toward maintaining the bird populations. Proposals to remove the top 6" of soil in some areas concern me greatly if it involves destroying current nesting bushes for tropicbirds, particularly if there are no data to show that the birds are currently being affected by any contaminants Since all the vegetation has the potential to be killed by roosting and nesting frigates and Red-footed Boobies ifthey move over to Johnston Island, FWS may decide that it is not worthwhile planting anything new, and just decide to use concrete rubble for habitat.

Dioxin Site. I have monitored the tropicbirds in this site for several years and have found no effect on any of the end points measured: reproductive success, adult masses and egg sizes. These parameters were compared to those of birds nesting in other areas of the Atoll. The HO site study conducted by Dr. Mike Fry found no significant affect on the nesting tropicbirds, nor on nest success (Fry 2000). It would be much better for the birds if this area were left alone and the bushes not destroyed.

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Other Potentially Contaminated Sites on Johnston Island. I cannot document any contaminants effects on tropicbirds nesting anywhere on Johnston Island over the past 19 years. There is no area that has reduced reproductive success. The birds nest under any available vegetation that provides shade, and under rubble or buildings as available. In studies conducted on tropicbirds and other species on the other islands of the Atoll, I also cannot document any effects from contaminants (Schreiber 2000). Most contaminant references suggest that if there is no longer an input of a contaminant, and there has been no effect on any of the end points measured in the birds, then there is no reason for concern (Huggett et al. 1989, Hoffman et al. 1990, Fox et al. 1991). I thus do not expect to see any effects in the birds in the corning years.

Pertinent Seabird Biology. None of these species feeds on land or picks up debris on land (Anderson, 1992, Ashrnole 1963, Diamond and Schreiber 2001, Gauger and Schreiber in press, Harrison, Hida and Seki 1983, Norton and Schreiber 2001). They may not do this because they do not feed while sitting on the water either. Thus, they would not be expected to sit and pick up things on land. Our data, collected since 1984, indicate that none ofthe Johnston Atoll seabirds are ingesting any contaminants that affect their reproductive success and survival (Schreiber 1999). Tropicbirds are highly philopatric, returning each year to exactly the same nesting bush. Once vegetation is removed, the birds nesting there often never nest again, and most of those that do nest again, do so within 500 feet oftheir original site (Schreiber 1999). They generally lose their mate when they cannot return to the nest bush to find them and may go several years before finding another. Many have been shown to never nest again.. Thus the loss of good nesting habitat means the loss of production of many chicks, essentially it is as if many adults were killed. Additionally, even if vegetation is replanted after an area has been cleared, much of the replanting will die, and it will take years for new vegetation to become appropriate nesting habitat. None of the nesting species of Johnston Atoll generally feed in lagoon (from 18 years of observations: Anderson 1992, Ashmole 1963, Diamond and Schreiber 2001, Gauger and Schreiber in press, Harrison et al. 1983, Norton and Schreiber 2001, Palmer 1962, Schreiber and Schreiber 1993, Schreiber et al. 1996). Infrequently a larval fish is found in the diet of a White Tern or Black Noddy, indicating that the bird may have fed in the lagoon, though these fish can be caught outside the lagoon also. A few young Brown Boobies or Black Noddies are seen playing in the lagoon as they first learn to fish. I would not expect any lagoon contaminants to be reflected in the birds. I do not expect new species to begin nesting on Johnston Atoll in any significant numbers once human inhabitants are gone. For instance, I would not expect a colony of Laysan or Blackfooted Albatross to form. They are colder water species (Whittow 1993a, b). There are a few records of albatross being sighted on Johnston, but they have not been documented to nest here successfully, even prior to human interference on the atoll (Amerson and Shelton 1976, Whittow 1993a, b).

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Future Protection of Birds I do not see any particular management concerns for the birds on Johnston Atoll that would require active intervention by people once the base is closed. There are no introduced predators that appear to need control. The currently present house mouse does little to no damage to any birds. If it were desired, Johnston is small enough that all the mice could be quickly eradicated with the proper program. Dr. Brian Bell, New Zealand, does this professionally and has assured me it would not be difficult on such a small atoll. I can provide contact information for him if desired. The one other concern for the birds is access by visitors that might disrupt colonies. Johnston Atoll is not on a main sailing route to any place and there is no fresh water available to people (if the island were abandoned). Both factors limit the number of people who would stop off at the island. If FWS is to keep staff on the Atoll, this would afford protection for the birds by controlling access of visitors to the island. Given the very limited number of expected boats coming by the island, I do not believe the bird populations would suffer if the island were abandoned. Some human disturbance is obviously tolerated by these species. If Johnston Atoll is left uninhabited, a few protective measures could be taken that might help protect the birds. 1) Fence all the area around the Johnston Island wharf (landing place for boats) with tall chainlink fence. If about 20 acres were left open to people, they would havc space to get off their boats and do repairs or whatever. 2) Post large signs on the fence and in other areas stating that it is a Refuge and visitors are prohibited from entering beyond the fence. Post signs on the out islands also. Most people will respect these signs. Also, many people are afraid of densely nesting birds, such as occur in a seabird colony, and would not go near them. 3) Signs could be posted that the island poses a radiation hazard (owing to the plutonium). 4) Visit the Atoll once a year during the height of the breeding season to do fence and sign repairs, and to assess status of the birds. 5) Possibly consider knocking down any docks at the out islands (East, North, Sand) and filling in part of the access channel to each to prevent people from easily gaining access to these islands. This would at least prevent people from pulling right up to the island in a deep hulled craft, causing them to have to go to the effort to row or motor a small craft to get to the island if they really wanted to see it. 6) Request that the U.S. Coast guard conduct overflights when transiting the area to look for unauthorized visitors.

Literature Cited Amerson, A. B., and P. C. Shelton. 1976. The natural history of Johnston Atoll, central Pacific Ocean. Atoll Research Bull. No. 192. Smithsonian Inst., Washington D. C. Anderson, D. J. 1992. The Masked Booby (Sula dactylatra). In The birds of North America, No. 73 (A. Poole and F. Gill, Eds.). Philadelphia, the Academy of Natural Sciences;

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Washington, D.C., the American Ornithologists Union. Ashmole, N. P. 1967. 1963. The biology of the Wideawake or Sooty Tern (Sterna fuscata) on Ascension Island. Ibis 103b: 297-364. Burger, J. 1993. Metals in avian feathers: bioindicators of environmental pollution. Rev. Environ. Toxicol. (E. Hodges Ed.) 5: 203-311. Burger, Joanna. 1995. A risk assessment for lead in birds. Joum. of Toxicology and Environmental Health 45: 369-396. Burger, 1. and M. Gochfeld. 200 I. Effects of chemicals and pollution on seabirds. In Biology of Marine Birds (E. A. Schreiber and J. Burger, eds.). CRC Press, Boca Raton, FL. Burger, J., K Parsons, T. Benson, T. Shukla, D. Rothstein, and M. Gochfeld. 1992. Heavy metal and selenium levels in young cattle egrets from nesting colonies in the northeastern U. S., Puerto Rico and Egypt. Arch. Environ. Contamin. and Toxicol. 23: 435-439. Clarkson, T. W., G. F. Nordberg, and P. R. Sager. 1985. Reproductive and developmental toxicity of metals. Scand. Journ. Work Environ. Health II: 145-154. Diamond, A., W., and E. A. Schreiber. 2001. The Magnificent Frigatebird Fregata magnificens. In The Birds Of North America, (A. Poole and F. Gill, Eds.). Philadelphia, the Academy of Natural Sciences; Washington, D.C., the American Ornithologists' Union. Finley, M. T., M. P. Dieter, and L. N. Locke. 1976. Sublethal effects of chronic lead ingestion in mallard ducks. Journ. Toxicol. Environ. Health 1: 929-937. Finley, M. T., and R. C. Stendell. 1978. survival and reproductive success of black ducks fed methyl mercury. Environ. Pollution 16: 51-64. Fox, G. A., B. Collins, E. Hayakawa, D. V. Weseloh, J. P. Ludwig, T. J. Kubiak, and T. C. Erdman. 1991. Reproductive outcomes in colonial fish-eating birds: a biomaker for environmental toxicants in Great Lakes food chains. II. Spatial variation in the occurrence and prevalence of bill defects in young double-crested cormorants in the Great Lakes, 1979-1987. Journal of Great Lakes Research 17: 158-167. Fry, D. M. 2000. Johnston Atoll avian risk assessment: tropicbirds nesting in the HO site on Johnston Atoll. Report to OHM Remediation Services, Kapolei, HI. Furness, R. W. and C. J. Camphuysen. 1997. Seabirds as monitors of the marine environment. ICES Joum. Marine Science 54: 726-737. Gauger, V., E. A. Schreiber. in press. The Great Frigatebird Fregata minor. In The Birds Of North America, (A. Poole and F. Gill, Eds.). Philadelphia, the Academy of Natural Sciences; Washington, D.C., the American Ornithologists' Union. Gochfe1d, M., and J. Burger. 1988. Effects oflead on growth and feeding behavior of young common terns (Sterna hirundo). Arch. Environ. Contam. Toxicol. 17: 513-517. Harrison, C. S., T. S. Hida, and M. P. Seki. 1983. Hawaiian seabird feeding ecology. Wildlife Mongraphs No 85. Heinz, G. H., D. J. Hoffman, and L. G. Gold. 1989. Impaired reproduction of mallards fed an organic form of selenium. Journ. Wildlife Management 53: 418-428. Hoffman, D. J., J. C. Franson, O. H. Pattee, C. M. Bunck and A. Anderson. 1985. Survival growth and accumulation of ingested lead in nestling American kestrels (Falco sparverius). Arch. Environ. Contam. Toxicol. 14: 89-94. Hoffman, D. J., B. A. Rattner, and R. J. Hall. 1990. Wildlife toxicology. Environ. Science and Toxicology 24: 276-283. Huggett, R. J., R. A. Kimerle, P. M. Mehrle, Jr., and H. L. Bergman, eds. 1989. Biomarkers: biochemical, physiological, and histological markers of anthropogenic sress. Soc. of Env. Toxicol. Chern.

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Kendall, R J., P. F. Scanlon and R T. DiGuilio. 1982. Toxicology of ingested lead shot in Ringed Turtle Doves. Arch. Environ. Contam. Toxicol. 11: 259-263. Koster, M. D., D. P. Ryckman, D. V. C. Wesloh, and J. Strnger. 1996. Mercury levels in Great Lakes herring gull (Lams argentatus) eggs, 1972-1992. Environ. Pollution 3: 261-270. Lewis, S. A., and R. W. Furness. 1991. Mercury accumulation and excretion in laboratory reared black-headed gull (Lams ridibundus) chicks. Arch. Environ. Contamin. Toxicol. 21: 316320. Lipton, J. H. Galbraith, J. Burger, and D. Wartenberg. 1993. A paradigm for ecological risk assessment. Environ. Manage. 17: 1-5. Norton, R, and E. A. Schreiber. 2001. The Brown Booby (Sula leucogaster). In The birds of North America. (A. Poole and F. Gill, Eds.). Philadelphia, the Academy of Natural Sciences; Washington, D.C., the American Ornithologists Union. Palmer, R S. 1962. Handbook of North American birds. Yale Univ. Press, New Haven. 567 pp. Pregill, G. K., D.W. Steadman, and D. R. Watters. 1994. Late quaternary vertebrate faunas of the Lesser Antilles; historical components of Caribbean biogeography. Bull. of Carnegie Museum of Natural History No. 30. Schreiber, E. A. 1999. Breeding biology and ecology ofthe seabirds of Johnston Atoll, central Pacific Ocean. Report submitted to Project Manager for Chern. Stockpile Demil., Aberdeen, MD. Schreiber, E. A. 2000. Breeding biology and ecology ofthe seabirds of Johnston Atoll, central Pacific Ocean. Report submitted to Project Manager for Chern. Stockpile Demil., Aberdeen, MD. Schreiber, E.A., and RW. Schreiber. 1993. The Red-tailed Tropicbird(Phaethon rubricauda).ln The birds of North America, No. 43 (A. Poole and F. Gill, Eds.). Philadelphia: the Academy of Natural Sciences; Washington, D.C.: the American Ornithologists Union. Schreiber, E.A., RW. Schreiber and G.A. Schenk. 1996. The Red-footed Booby (Sula sula). In The birds of North America, No. 241 (A. Poole and F. Gill, Eds.). Philadelphia, the Academy of Natural Sciences; Washington, D.C., the American Ornithologists Union. Steadman, D. W. 1989. Extinction of birds in eastern Polynesia: a review ofthe record, and comparisons with other Pacific Island groups. Journ. Archaeo. Science 16:177-205. Steadman, D. W. 1995. Prehistoric extinctions of Pacific island birds: biodiversity meets zooarchaeology. Science 267:1123-1131. Stoewsand, G. S., J. L. Anderson, W. H. Gulenmann, and D. J. Lisk. 1978. Influence of dietary calcium, selenium and methyl mercury on eggshell thickness in Japanese quail. Bull. Environ. Contam. Toxicol. 20: 135-142. Whittow, J. C. 1993a. Black-footed Albatross (Diornedea nigripes). In The Birds of North America, No. 65 (A. Poole and F. Gill eds.). The Academy of Nat I. Sciences, Philadelphia, and The American Ornithologists' Union, Washington, DC. Whittow, J. C. 1993b. Laysan Albatross (Diornedea irnrnutabilis). In The Birds of North America, No. 66 (A. Poole and F. Gill eds.). The Academy of Natl. Sciences, Philadelphia, and The American Ornithologists' Union, Washington, DC. Work, T. M., and M. R. Smith 1996. Lead exposure in Laysan albatross adults and chicks in Hawaii: prevalence, risk factors, and biochemical effects. Arch. Environ. Contam. Toxicol. 31: 115-119.

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Johnston 2001 Seabird Report - Schreiber

APPENDIXB

EFFECTS OF A CHEMICAL WEAPONS INCINERATION PLANT ON RED-TAILED TROPICBIRDS E. A. SCHREIBER,1,2 National Museum of Natural History, MRC 116, Washington, D.C. 20560, USA PAUL F. DOHERTY, JR., Warnell School of Forest Resources, University of Georgia, Athens, GA 30602, USA, and Bird Banding Laboratory, USGS Patuxent Wildlife Research Center, Laurel, MD 20706, USA GARY A. SCHENK, 4109 Kames Court, Alexandria, VA 22306, USA

Abstract From 1990 to 2000, the Johnston Atoll Chemical Agent Disposal System UACADS) incinerated part of the U.S. stockpile of chemical weapons on Johnston Atoll, central Pacific Ocean, which also is a National Wildlife Refuge and home to approximately a half-million breeding seabirds. The effect on wildlife of incineration of these weapons is unknown. Using a multi-strata mark-recapture analysis, we investigated the effects of JACADS on reproductive success, survival, and movement probabilities of red-tailed tropicbirds (Phaethon rubricauda) nesting both downwind and upwind of the incineration site. We found no effect of chemical incineration on these trapicbird demographic parameters over the 8 years of our study. An additional 3 years of monitoring tropicbird demography will take place, post-incineration.

JOURNAL OF WILDLIFE MANAGEMENT 65(4):685-695

Key words: chemical munitions, contaminants, heavy metals, ]ACADS, Johnston Atoll, long-term monitoring, Phaethon rubricauda, red-tailed tropicbird, reproductive success, survival.

Reproductive success and annual survivorship are 2 parameters needed for demographic population models. There are few estimates of these parameters for seabirds, and only 2 studies that provide good estimates for pelagic Pelecaniformes (Montevecchi et a!. 19'84, Anderson 1993). A 17-year elTort onJohnston Atoll, Central Pacific Ocean, during which we collected demographic data pertaining to these vital ra.tes, now allows us to estimate these parameters in redtailed tropicbirds for the first time. We consider I aspect of this long-term demographic study: the effect of disposing of the U.S. stockpile of chemical weapons stored at Johnston Atoll on red-tailed tropicbirds. The safe disposal of such weapons is of concern, as there are 7 states in the U.S. where chemical agents are stored (U.S. Army 1994). Incineration of the stockpile stored on Johnston Atoll (l6°45'N, 169°31'W; Fig. I) was completed in December 2000 in what is called the Johnston Atoll Chemical Agent Disposal System. This was the first operational facility of its kind (beginning operation in 1990). As well a$ being the home ofJACADS, Johnston Atoll is also a National Wildlife Refuge. It is a coral atoll made up of 4 small islands, 1.150 km southwest of Hawaii. The refuge is located in the

belt of easterlies that drive the North Equatorial Current, and it provides breeding sites for approximately a half-million seabirds of 13 species. Because of its status as a National Wildlife Refuge, there was concern for the safety and survival of the wildlife during the chemical weapons incineration process. An integral part of the disposal process has been monitoring effects of the incinerator on wildlife (Schreiber 1994, 1996, 1999; Schreiber and Schreiber 1993; Schreiber et al. 1996). Two of the major environmental concerns during operation of the plant were (1) the presence of trace amounts of heavy metals emitted from the smokestack, and (2) potential leaks during the moving of munitions to the incinerator (Raytheon Engineers and Contractors 1996). Both concerns could affect birds nesting downwind of the incinerator. The incinerator and munitions storage site are on the sOllthwest end of Johnston Island (Fig. I), the downwind end, Red-tailed tropicbirds are the only species that

1301) km to MIdway Island

t Downwind

1

E-mail: [email protected]

2

~hiling address: 4lO9 Komes COlIrt, Alexandria. VA

22306, USA, 685

!

N Upwlod Incinoralor

----. 1150 km to Uawall 4501) km \0 .san f''ln,;iHCQ

Fig. 1. Johnston Island with the location of tile incinerator, downwind, and upwind breeding areas designated.

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THE EFFECTS OFJACADS ON TROPICBlRDS • Schreibere, at.

nest in any numbers (about 500 pairs in 1999) in the area downwind of the smokestacks and near the munitions storage bunkers. If the storage and incineration of chemical weapons had deleterious effects, we predicted that reproductive success and survival of redtailed tropicbirds would be lower at downwind sites and birds would be more likely to move away from downwind sites to upwind sites, than vice versa. We compared reproductive success and estimated survival and movement rates using modern mark-recaptt;tre survivorship analysis techniques (Lebreton et al. 1992, Schwartz and Seber 1999) for red-tailed tropicbirds nesting in areas located both upwind and downwind of the JACADS incinerator.

METHODS Study Area Johnston Atoll consists of 2 entirely man-made islands and 2 small sand islands that were augmented by dredging, forming a total landmass on the atoll of about 2.6 km 2 • Military construction and dredging began in 1939, and the added landmass has allowed increasing numbers of seabirds to use the atoll for nesting and roosting. The wind is from the east, except during £1 Nino-Southern Oscillation (ENSO) evenL, and on a few still days during the year (generally in Jun-Jul). During the beginning stages of an ENSO event, the wind stops and shifts to the west (Schreiber and Schreiber 1993). The incinerator sat on the downwind side of Johnston Island (southwest end; Fig. 1). No incineration was carried out during days of westerly winds. Thus, there was no potential for contamination of birds nesting upwind from the incinerator.

Study Species Tropicbirds invariably lay I egg, and reproductive success each year has varied from 68-85% (Schreiber 1999). These birds are philo patrie and return to the same nest site each year after they nest successfully. Individuals may re-mate if a mate does not return t year, but generally they establish a new nest within 150--200 m of the original nest site if possible (Schreiber 1999). Tropicbirds exhibit deferred maturity and first begin breeding at a mean of 3 years of age (range 2-6; Schreiber and Schreiber 1993). We believe that well over 95% of birds recaptured are nesting birds, since only a few non-nesting birds (birds not with an egg or chick) are caught each year.

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Birds do not roost on the island, and courtship is aerial, limiting potential for capture of non-nesting birds. Tropicbirds feed offshore and out of sight of the atolL Since they do not feed in the lagoon, there is no ingestion pathway for local reef fish to the birds. During the nonbreeding season, these birds are not seen on land, and we have no data on where they go.

Data Collection From 1984 through 1999, we made 2 to 4 visits each year to Johnston Atoll, totaling 1 to 2 months per year. We monitored nests for eggs and hatching success, banded all bandable chicks on each visit, and attempted to recapture as many adults as possible. In 1986, the U.S. Fish and Wildlife Service stationed personnel on the atoll, and they have additionally· banded and recaptured birds. Bands showing wear were replaced, and band loss is unlikely to have occurred. From 1983 through 1999, 25,824 tropicbirds were banded. Banding locations on the atoll by island and ages of birds banded were recorded (adult or chick). Approximately 45% of the nesting adults were recaptured each year and their bands read. Recapture effort differed somewhat by area and year; for instance, more effort was made to recapture adults in the downwind areas after the incinerator began operation. This study and previous studies indicate little or no interisland mo\·ement of adults within Johnston Atoll, or to other atolls (Schreiber and Schreiber 1993, Schreiber 1999). Within Johnston Atoll, there is an average probability of movement from 1 island to another between ,consecutive breeding seasons equaling 0.0079 (SE ~ 0.0002). All birds caught and banded on Johnston Island ha\·e been designated as being up- or downwind of the JACADS plant. Birds were considered in the downwind area if their nests fell within the smokestack plume outfalkone (Fig. I). Clear zones of no nests occurred between the upwind and downwind areas except for 1 area on the northwest side of the island that contained 5-8 nests. Birds on the northwest side of the island were considered to be upwind. All other birds outside of this downwind area were considered to be in the upwind area. In our analysis, only birds nesting on Johnston Island since 1992 were used because birds on the outer islands were banded with less intensity and experienced disturbance from other nesting species (which did not occur on Johnston Island). The outer

J. Wild!. Manage. 65(4):2001

THE EFFECrS OF JACADS ON TROPICBIRDS • Schreiber et al.

islands also differed in vegetation. We focused on adult tropicbirds in relation to the JACADS plant since tropicbirds exhibit delayed breeding (some do not breed until 6 years Dfage), and we did not have enough data to properly analyze juvenile survival taking into account age-specific breeding probabilities (Clobert et al. 1994; Spcnde10w et aL, in press; Williams et aL, in press). Age-specific breeding probability is a source of heterogeneity that needs to be estimated when estimating juvenile survival in birds with delayed breeding (Williams et aI., in press).

Statistical AnalysIs To test for differences in reproductive success, we used a i-sample t-test on the yearly differences in reproductive success (number fledged/number eggs) in upwind minus downwind areas. By examining the difference in reproductive success, we control for year and overall island effects and focus on the difference between the 2 areas. [f no differences occurred consistently in this measure, we would expect the difference to be O. We followed the analytical strategies of Lebreton et aL (1992) and Burham and Anderson (1998) by employing Cormack:Jolly-Seber (CJS) open-population capture-recapture models (Cormack 1964, Jolly 1965, Seber' 1965) and extensions as available in program MARK (White and Burnham 1999). Specifically, we employed a multi-strata approach, originally developed by Amason (1972, 1973) and recently reviewed by . Nichols ((996) to estimate survival and movement probabilities. This approach has been used successfully by Hestbeck et aL (1991) and Spendelow et £11. (1995) in estimating movement between and survival rates within differing study sites of Canada geese (Bmnta ranadensis) and roseate terns (Sterna dougal/il), respectively. Using this modeling appl-oach, we estimated the probability of recapture and survival in each area (downwind and upwind) as well as the probability of movement between the 2 areas. The assumptions required by these multi-strata models are similar to those required by the CJS model, namely (I) recapture and transition probabilities Ztre the same for all marked birds found in a partiCltlar area and sampling period; (2) birds behave independently with respect to survival, recapture, and movement probabilities: (3) marks are not lost; and (4) alls.:tlllpies are instc.'1ntaneous. Our study and study species met. these assumptions. Red-tailed tropicbirds do not flock and are thought to behave independently except during

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the breeding season (assumption 2). Although this species lives long enough to have bands wear and fall off, the population was monitored very closely, and worn bands were replaced on a regular basis (assumption 3). The assumption (4) that sampling is instantaneous can never be met, but we restricted our sampling to the breeding season. The length of sampling should be short to accommodate the length of time between sampling, and sampling should not occur during high mortality or movement. We believed this was the case in our study. We saw little mortality at the breeding grounds, and movements beu.veen breeding sites occur between sampling occasions. Because of these facts, we· believe that this species is an ideal candidate for this type of modeling approach. Additionally, we ran bootstrap goodness-f:-fit tests to assess the fit of a general model to our data (Burnham and Anderson 1998) as available in program MARK (White and Burnham 1999). Although a bootstrap goodness-f-fit test is not available for a multi-strata parameterization in program MARK, I exists for the CJS live recapture model, which we used. Specifically, we separately ran bootstrap goodness-f-fit tests for general, time-specific CJS models for birds nesting both upv.rind and downwind of the incineratoI: The bootstrap goodness-of-flt test probes for overdispersion in the data and, if warranted, c· (variation inflation factor) can be estimated and used to adjust subsequent estimates and statistics. V\'e took a conservative approach and used c- if the boot 20 days) chicks. Overall reproductive success was estimated as the number of fledged chicks from sampled nests divided by the number of sampled nests in which an egg was laid. We usedcapture-mark-recapture analyses (Cormack 1964, Jolly 1965, Seber 1965) as modified by Spendelow et al. (2002) and Williams et al. (2002) to estimate adult and juvenile probabilities of recapture and survival as well as age-specific breeding probabilities. Specifically we used the method outlined in Williams et al. (2002) which

12 follows the approach ofClobert et al. (1994). Following Williams et al. (2002) we defmed the following threshold ages:

k - the fIrst age at which an animal can breed m - the age by which all animals breed and the following model parameters:

p:+ - the probability that a marked breeder (de~oted as age k+) in the stndy population at sampling period i is captnred or observed during period i;

"':+ - the probability that a marked animal of age> k survives until period i+ I and remains in the population; "'; - the probability that a young animal (age 0) released at sampling period i survives until sampling period Hk;

ai') - the probability of breeding for an animal of age v at sampling period i that has not previously bred. Following Williams et al. (2002) we made the following assumptions with this modeling parameterization: I) the age k of fIrst possible breeding is known; 2) all animals become breeders by age m; 3) every young animal released at age 0 in sampling period i has the same probability "'; of snrvival until sampling period Hk; 4) every marked animal aged >k in sampling period i, regardless of breeding statns, has the same probability

",t of survival until sampling period i+ I;

13 5) every marked breeding animal present in the population at sampling period i has the same probability p:+ of being recaptured; 6) marked prebreeding animals of age> 0 are not exposed to sampling efforts and have a probability of 0 of being captured in any sampling period; 7) every marked prebreeding animal of age v, where k