Habitat use and distribution of listed neotropical ...

Habitat use and distribution of listed neotropical migrant songbirds in northeastern British Columbia

Submitted to: Ministry of Environment, Lands and Parks Fort St. John, British Columbia

Submitted by: 1

2

3

Stephen Bennett , Peter Sherrington , Pierre Johnstone , and Bruce Harrison 1

Mirkwood Ecological Consultants Ltd. Winlaw, BC 2

3

4

Cochrane, Alberta

Ministry of Environment, Lands, and Parks Fort Nelson, BC 4

Fort St. John, BC

Primary Contact: S. Bennett (250) 365 0765 email [email protected]

HABITAT USE and DISTRIBUTION of LISTED NEOTROPICAL MIGRANTS

1/22/2015

Abstract The primary objective of this paper is to summarize the distribution and habitat use of red and blue listed neotropical migrant songbirds (hereafter referred to as ‘listed’ species) in the Fort Nelson Forest District (FNFD) in northeastern British Columbia (BC). Data was summarized from two main sources: anecdotal data and studies conducted prior to 1996, and four Forest Renewal BC (FRBC) studies conducted since 1996. We also compared the relative density of listed species (pairs/ha) to densities reported in the centre and eastern parts of their breeding range. The dominant biogeoclimatic zone in the FNFD is the Boreal White and Black Spruce zone (68% of the district) which represents a large part of the mixedwood boreal forest found in BC. The major tree species are white and black spruce, lodgepole pine, tamarack, subalpine fir, paper birch, balsam poplar, and trembling aspen. Northeastern BC is home to six listed species that are rare or unrecorded in the rest of the province: baybreasted warbler (BBWA), black-throated warbler (BTNW), Canada warbler (CAWA), Cape May warbler (CMWA), Connecticut warbler (COWA), and Philadelphia vireo (PHVI). The listed species are of particular management concern because they have a relatively limited distribution in BC, they use habitats often targeted for forest development, and little is known about their distribution and breeding ecology in BC. The number of neotropical migrants recorded throughout the FNFD appeared to decrease in studies the farther north and west they were in the FNFD. The Prophet River study site in the southern portion of the FNFD had the most neotropical migrants and the Smith River in the northwest portion of the FNFD had the least. The Prophet River was the only site where all six listed species were recorded and it is the only site where BTNW, COWA, and PHVI have been recorded in the FNFD. All the studies in the FNFD found listed species using similar habitats to those described in the literature. Mature and old forests appeared to be preferred by all listed species except the COWA and the PHVI which used pole stage aspen. All listed species were generally restricted to valley bottom sites and mid slopes along major rivers except CMWA which were found in mid to upper elevations throughout the FNFD. BTNW and COWA were rare and are likely restricted to the southern portion of the FNFD. PHVI also appeared to be rare but were sporadically distributed throughout the eastern portion of the FNFD and as far north as southeastern Yukon. BBWA, CAWA, and CMWA were all common in their preferred habitats. CMWA were more widely distributed than other listed species and their breeding range likely extends as far west as Watson Lake, Yukon. The FNFD has a unique assemblage of "eastern" boreal and "western" montane birds and also marks the southern limit of such northern birds as Arctic Terns and Pacific Loons and the northern limit of southern birds like black terns and soras. The densities of common listed species (BBWA, CAWA, CMWA) and several other neotropical migrants (magnolia warblers, ovenbirds, Tennessee warblers) are similar to densities reported from the centre and eastern parts of their ranges. This was unexpected since the FNFD is at the western extent of the listed species’ breeding range and suggests that the FNFD has optimal habitat for these listed species and others. We outline preliminary management recommendations. However, more research is required to determine how applicable findings from eastern neotropical research are to the western portion of the boreal forest. These studies suggest western portions of the boreal forest may have different ecological characteristics and may respond differently to human development.

Mirkwood Ecological Consultants Ltd., Winlaw, BC

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Table of Contents ABSTRACT .................................................................................................................................................. ii LIST OF TABLES ........................................................................................................................................iv 1.0 INTRODUCTION ................................................................................................................................... 1 1.1 BACKGROUND ............................................................................................................................................ 1 1.2 RESOURCE DEVELOPMENT STATUS IN THE FNFD ...................................................................................... 1 1.3 OBJECTIVES: ............................................................................................................................................... 2 1.4 INFORMATION SOURCES ............................................................................................................................. 2 1.5 ACKNOWLEDGMENTS ................................................................................................................................. 2 2.0 STUDY AREA ......................................................................................................................................... 2 3.0 METHODS............................................................................................................................................... 5 3.1 SAMPLE SITES AND SURVEY TECHNIQUES ................................................................................................... 5 3.2 BREEDING RANGE DELINEATION ................................................................................................................ 5 3.3 HABITAT USE AND RELATIVE ABUNDANCE ................................................................................................ 5 4.0 RESULTS ................................................................................................................................................. 6 4.1 GENERAL.................................................................................................................................................... 6 4.2 BAY-BREASTED WARBLER .......................................................................................................................... 7 4.2.1 Abundance/Population Status ............................................................................................................ 7 4.2.2 Distribution ........................................................................................................................................ 8 4.2.3 Habitat Use......................................................................................................................................... 8 4.3 BLACK-THROATED GREEN WARBLER ........................................................................................................ 13 4.3.1 Abundance/Population Status .......................................................................................................... 13 4.3.2 Distribution ...................................................................................................................................... 13 4.3.3 Habitat Use....................................................................................................................................... 13 4.4 CANADA WARBLER ................................................................................................................................... 13 4.4.1 Abundance/Population Status .......................................................................................................... 13 4.4.2 Distribution ...................................................................................................................................... 15 4.4.3 Habitat Use....................................................................................................................................... 15 4.5 CAPE MAY WARBLER ............................................................................................................................... 15 4.5.1 Abundance/Population Status .......................................................................................................... 15 4.5.2 Distribution ...................................................................................................................................... 17 4.5.3 Habitat Use....................................................................................................................................... 17 4.6 CONNECTICUT WARBLER ......................................................................................................................... 17 4.6.1 Abundance/Population Status .......................................................................................................... 17 4.6.2 Distribution ...................................................................................................................................... 17 4.6.3 Habitat Use....................................................................................................................................... 20 4.7 PHILADELPHIA VIREO ............................................................................................................................... 20 4.7.1 Abundance/Population Status .......................................................................................................... 20 4.7.2 Distribution ...................................................................................................................................... 20 4.7.3 Habitat Use....................................................................................................................................... 20 5.0 DISCUSSION ......................................................................................................................................... 22 5.1 STATUS AND DISTRIBUTION ...................................................................................................................... 22 5.2 ABUNDANCE AND HABITAT USE............................................................................................................... 22 6.0 MANAGEMENT RECOMMENDATIONS/FUTURE RESEARCH ............................................... 26


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7.0 CONCLUSION ...................................................................................................................................... 27 8.0 LITERATURE CITED ......................................................................................................................... 29 APPENDIX I. SUMMARY OF DENSITIES ESTIMATES FOR SPRUCE BUDWORM SPECIALISTS (CMWA, BBWA, AND TEWA) AND NON-SPRUCE BUDWORM SPECIALISTS (OVEN, CAWA, AND MAWA) FROM EASTERN BOREAL FORESTS AND FNFD. ..................... 33

List of Figures FIGURE 1. LOCATION OF FORT NELSON FOREST DISTRICT AND STUDY AREAS IN NORTHEASTERN BC. ............ 4 FIGURE 2. NUMBER OF NEOTROPICAL MIGRANT SPECIES RECORDED BY STUDY SITE (PROPHET RIVER DATA FROM SAVIGNAC 1998). ........................................................................................................................... 6 FIGURE 3. THE NUMBER OF LISTED SONGBIRD SPECIES RECORDED IN THE FNFD SINCE 1996 BY STUDY AREA.7 FIGURE 4. RECENT RECORDS OF BAY-BREASTED WARBLERS IN THE FNFD COMPARED TO THEIR HISTORIC BREEDING RANGE. .................................................................................................................................... 9 FIGURE 5. RECENT RECORDS OF BLACK-THROATED GREEN WARBLERS IN THE FNFD COMPARED TO THEIR HISTORIC BREEDING RANGE. ................................................................................................................... 14 FIGURE 6. RECENT RECORDS OF CANADA WARBLERS IN THE FNFD COMPARED TO THEIR HISTORIC BREEDING RANGE. ................................................................................................................................................... 16 FIGURE 7. RECENT RECORDS OF CAPE MAY WARBLERS IN THE FNFD COMPARED TO THEIR HISTORIC BREEDING RANGE. .................................................................................................................................. 18 FIGURE 8. RECENT RECORDS OF CONNECTICUT WARBLERS IN THE FNFD COMPARED TO THEIR HISTORIC BREEDING RANGE. .................................................................................................................................. 19 FIGURE 9. RECENT RECORDS OF PHILADELPHIA VIREOS IN THE FNFD COMPARED TO THEIR HISTORIC BREEDING RANGE. .................................................................................................................................. 21 FIGURE 10. NUMBER OF HA OF FOREST DEFOLIATED BY THE SPRUCE BUDWORM IN THE FNFD: 1989-1996 (TAYLOR 1996, TAYLOR 1997). ............................................................................................................. 23 FIGURE 11. COMPARISON OF THE DENSITIES (PAIRS/HA) OF BUDWORM SPECIALISTS. ..................................... 24 FIGURE 12. COMPARISON OF THE DENSITIES (PAIRS/HA) OF NON-BUDWORM SPECIALISTS. ............................. 25

List of Tables TABLE 1. SUMMARY OF HABITAT ATTRIBUTES AND SITE SERIES ASSOCIATIONS FOR LISTED NEOTROPICAL MIGRANTS IN THE FORT NELSON FOREST DISTRICT. ............................................................................... 10


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1.0 Introduction 1.1 Background The Boreal Region is the only forested circumpolar terrestrial biome, and includes very large forested wilderness areas interspersed with very large peatland wilderness areas, covering approximately 1.6 billion ha (Pastor et al. 1998). Today, the boreal forest is developed over significant portions of previous ranges, largely as a result of forest harvesting (Niemi et al. 1998); other significant causes of alienation of boreal lands include agriculture, energy and mines exploration, and urban development. In British Columbia (BC), the Boreal White and Black Spruce biogeoclimatic zone (BWBS) exemplifies the lower elevation component of the Boreal Region. The BWBS zone occurs throughout northern BC, but is most common in the Fort Nelson Forest District (FNFD) in the northeastern portion of the province. The Fort Nelson Land and Resource Management Plan provides for four different categories of development zones (LRMP 1997). Much of the BWBS falls in the “enhanced resource development zone” and as such has a lower biodiversity emphasis option (i.e. timber supply and gas development primary management options) (MOF and MELP 1995). A number of songbirds that are rare or unrecorded in the rest of the province breed in the northeastern portion of BC (Enns and Siddle 1996), including six which are listed as either ‘red’ or ‘blue’ species by the Ministry of Environment, Lands and Parks (MELP), Conservation Data Centre (CDC) (hereafter referred to as ‘listed’ species) (MELP 1998). Red listed species are considered to be endangered or threatened in B.C. and blue listed species are considered to be vulnerable or sensitive (MELP 1998). Red listed species believed to breed in the FNFD include the Cape May warbler (CMWA) (Dendroica tigrina), the baybreasted warbler (Dendroica castanea) (BBWA), the Connecticut warbler (Oporornis agilis) (COWA), and the black-throated green warbler (Dendroica virens) (BTNW); blue-listed species include the Canada warbler (Wilsonia canadensis) (CAWA) and the Philadelphia vireo (Vireo philadelphicus) (PHVI) (MELP 1998). Very few nesting sites have been confirmed in BC and information is limited regarding the distribution and abundance of these species. Although their habitat requirements have been described in eastern North America, it is still unclear how applicable the descriptions are to northeastern B.C. These species are of particular management concern, as they are all ‘neotropical migrants’, meaning they breed in temperate regions but migrate long distances from their wintering grounds in the tropical Americas. Recent studies have indicated a widespread decline in populations of neotropical migrants, and provincial status reports on these species suggest that there could be significant negative impacts from forest development (Cooper et al. 1997a-f). Neotropical migrants tend to be more abundant in landscapes with a greater proportion of forest and wetlands, fewer edge habitats and larger forest patches (Flather and Sauer 1996), and recent studies suggest that they can be negatively affected by forest harvesting (Schmiegelow et al. 1997). Brown-headed cowbirds are known to parasitize the nests of many songbirds, and it is thought that the rates of nest parasitism rise with increased levels in forest fragmentation (Brittingham and Temple 1983, Kerlinger and Doremus 1981). However, most of the studies supporting these findings have come from eastern North America and there is debate about their applicability to western forests (Bunnell 1998).

1.2 Resource Development Status in the FNFD There are two principal natural resource development industries in the FNFD: forest harvesting, and oil and gas development. The forest industry has had a significant and growing impact since the early 1970s. Original development targeted the valley bottom white spruce (Picea glauca) stands and as a result these stands are relatively rare; forest companies have now begun to target upland sites. Initial annual cuts were approximately 600,000 m3/year (M. Thorp, Pers. Comm.) and indications are that cuts will increase, particularly in the upland deciduous and mixedwood stands. It is difficult to determine


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the actual area of land impacted by the forest industry to date, but one estimate is approximately 55,000 ha based on an annual harvest of 1,500 ha/yr. (M. Thorp, Pers. Comm.). The natural gas industry has been active in the FNFD since the 1950’s (LRMP 1997). Land development activities are based on the subsurface characteristics, and affect all habitat types in the district. Operations begin with seismic exploration, typically straight lines with a bulldozer, which may be hundreds of kilometres long. Seismic activity is increasingly laid out in a grid pattern, over hundreds of square km, to provide a three dimensional image of the subsurface characteristics. Seismic lines are not planted and are often used for future access in subsequent development projects. The result is a bewildering pattern of intersecting straight lines, over the entire district. Once a likely gas source has been pinpointed, a well site is cleared, typically 1.5 to 5 ha, and a drilling rig is installed. If the well is productive, a field consisting of several wells may be developed. Hundreds of wells per year are drilled. Together, exploration and development may have cleared an average of 1,500 ha per year since the 1970s, or approximately 57,000 ha to date (M. Thorp, Pers. Comm.). Habitat impacts include random, patterned, and large scale fragmentation of land; noise, air, water, and land pollution, and widespread access into wilderness areas. Site specific effects may appear minor when compared to large clearcuts, which can replace entire old stands with early seral stage habitat; however, the cumulative effects of oil and gas development may be considerable although they have not been formally assessed.

1.3 Objectives: The objectives of this paper were to:  summarize FNFD bird inventory results;  summarize the distribution and habitat use of listed forest dwelling neotropical migrants (BBWA, BTNW, CAWA, CMWA, COWA, PHVI);  comment on the relative abundance of species compared to the centre of their range;  comment on possible impacts from forestry and mining; and  suggest future research required.

1.4 Information Sources This paper primarily draws on the distribution and habitat data from the following sources: the Canadian Wildlife Service (CWS) in the Yukon and Northwest Territories (NWT), the CDC, and the Ministry of Environment songbird inventories in FNFD (MacNaughton 1995, Bennett and Enns 1996, Enns and Siddle 1996, Bennett et al. 1998, Savignac 1998, Bennett 1999).

1.5 Acknowledgments We would like to thank Lisa Wilkinson of the Ministry of Environment in Fort St. John for securing funding for these projects, reviewing the papers, and providing mapping and technical support throughout the projects. We are very grateful to Geoff Haines, also of the Ministry of Environment in Fort St. John, who produced all the maps for this paper and our conference presentation in Kamloops. Mike Gill, Craig Machtans, Wendy Nixon, and Pam Sinclair of CWS and Cameron Eckert of Canadian Parks also provided insightful comments, reports, and preliminary data. Timberland Consultants and Pandion Ecological Research of Nelson , BC provided information on the Prophet River bird inventory. Carl Savignac was the author and field biologist for the Prophet River study. The staff of the Ministry of Forests (MOF) and Slocan Forest Products in Fort Nelson also provided much needed resources and local knowledge which increased our efficiency in the field.

2.0 Study Area


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The FNFD is bound in the east by Alberta, in the north by the Yukon and NWT, in the west by the Northern Rocky Mountains, and on the south by the Fort St. John and Mackenzie Forest Districts (Figure 1). It is the second largest forest district in BC covering approximately 8.2 million ha. The BWBS is the dominant biogeoclimatic zone, found over 68% of the district. This landscape features long and very cold winters, where monthly average temperatures are below 0 C for half the year (Meidinger and Pojar 1991). The major tree species are white and black spruce (Picea mariana), lodgepole pine (Pinus contorta), tamarack (Larix larcina), balsam fir (Abies balsamea), paper birch (Betula papyrifera), balsam poplar (Populus balsamifera), and trembling aspen (Populus tremuloides). Forest fires are the dominant natural disturbance, though frequent outbreaks of defoliating insects also occur (MOF and MELP 1995). The district produces relatively large white and black spruce, balsam poplar, and aspen compared to other neighboring boreal forest districts (D. Patterson, Pers. Comm.). The high productivity of forests in the FNFD is due to its relatively high topographic complexity, extensive riparian forest habitat associated with large rivers, coarse textured well drained soils, high precipitation, and high latitude (giving long summer daylight hours). Three different Ecoprovinces and accompanying Ecoregions are represented in the study area (Demarchi 1990): the Northern Boreal Mountains (Muskwa Ranges, Muskwa Foothills), Boreal Plains (SikanniBeatton Plateau), and Taiga Plains (Fort Nelson Lowlands). Elevations range from < 300 m in the eastern and central portions of the study area to over 1000 m in the west. The following descriptions of the three ecoprovinces in the study area are summarized from Demarchi (1990). The Muskwa Ranges and Muskwa Foothills of the Northern Boreal Mountains are located along the western margin of the study area. This is a rugged area of hills, valleys and high mountains. In the mountains, cold air drainages are common and sparse valley vegetation is normal. Two different biogeoclimatic zones were sampled in the Muskwa Foothills and Ranges, the BWBSmw2 at lower elevations and the Spruce Willow Birch zone (SWB) at mid elevations. Conifer stands dominated by white spruce are common in forested areas of the Muskwa Ranges. Mixed stands of white spruce and trembling aspen are prevalent in the Muskwa Foothills. Stands of lodgepole pine are common on some upland escarpments of the Muskwa Foothills. Precipitation is evenly distributed between the summer and winter months. The Boreal Plains Ecoprovince is situated south and west of the Fort Nelson Lowlands. It extends eastward for hundreds of kilometres occurring in Alberta, Saskatchewan, Manitoba and the southern NWT. The climate is continental; there are no barriers to cold arctic air in winter and the climate is generally dry. Vegetation is dominated by the BWBS, especially in the northern portion of the Boreal Plains in the Sikanni-Beatton Plateau Ecosection which is co-incident with the southwest and western portions of the study area. The Taiga Plains Ecoprovince/Fort Nelson Lowland Ecoregion comprises the bulk of the land in the study area (in BC, the Taiga Plains Ecoprovince consists of one Ecosection). This area is the most northeastern portion of the province. Cold, dense arctic air flows into this area quite commonly during the winter and spring months. During the summer months the intersection of Pacific and Arctic air masses gives rise to periods of unstable weather. There are several large river systems in the Fort Nelson Lowlands including the Fort Nelson, the Muskwa and the Liard Rivers. This area is entirely dominated by the BWBS. The Fort Nelson lowlands are a repeating pattern of productive upland stands of aspen and white spruce and lowland areas of muskeg and black spruce bog. Very subtle changes in topography result in significant changes in forest cover composition (and therefore habitat type), driven largely by the depth of the water table.


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Figure 1. Location of Fort Nelson Forest District and study areas in northeastern BC.


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3.0 Methods 3.1 Sample sites and survey techniques Since 1996, the Ministry of Environment, Lands, and Parks (MELP) has initiated four bird inventories in the FNFD to gain a better understanding of boreal forest bird communities. These studies have been funded by Forest Renewal BC (FRBC). Below we summarize the survey techniques and habitats sampled since 1996. For more details please refer to the specific reports. In 1996 we used transects to survey birds in a roadless area along the Liard River known as the “Big Bend” (Bennett and Enns 1996) (Figure 1). The Liard River is the main drainage system in FNFD and flows into the Mackenzie River in the NWT. The area has some of the last stands of age class 9 (>250 yr. old) spruce riparian habitat in the district. A 15 km stretch of river was surveyed using boat access, and transects were run from valley bottom to height of land on the south side of the river, a distance of about 3-4 km. In 1997 a survey of northern goshawks (Accipiter gentilis) was conducted using call playbacks throughout the FNFD, mostly west and north of Fort Nelson in mature and old forest types (Figure 1). A five minute listening period was used to record all birds before playbacks started. Listed species were also recorded between call playbacks and during reconnaissance surveys throughout the study. In 1998, three new sites were surveyed: the Smith River, Dunedin River (Bennett 1999), and Prophet River (Savignac 1998). We used standardized 10 minute point counts spaced 200 m apart to survey birds at the Smith and Dunedin Rivers. Terrestrial Ecosystem Mapping (TEM) at 1:50,000 was available for the Smith and Dunedin sites and we stratified the area based on structural stage and dominant site series. The Prophet River study used 5 minute point counts 200 m apart, to sample birds in general forest types (i.e. mature mixed, mature deciduous, etc.) (Savignac 1998). The Smith River flows into the Liard River in the far northwestern corner of the FNFD. No logging or mineral exploration activities have taken place in the drainage but a large fire in the early 1980’s burned the upper 25% of the drainage. The Dunedin is a large river flowing into the Liard River from the south and has its headwaters near Stone Mountain Provincial Park. We sampled two sites in the Dunedin River: a 30-40 ha area surrounding an airstrip on a plateau and some old growth riparian habitat along the Dunedin River. Both sites were fly-in access. The Prophet River flows along the Alaska Highway south of Fort Nelson and enters the Muskwa River just west of Fort Nelson. The study site focused on a mix of stands mainly along the highway 50-100 km south of Fort Nelson (Savignac 1998). For the remainder of this report we will use the following terms when discussing the different study sites:  Smith River - within the Smith River drainage and accessed by the Smith River FSR.  Dunedin airstrip - an area accessed by the Dunedin airstrip between Torpid Creek and the Dunedin River.  Dunedin River - valley bottom of Dunedin River accessed by helicopter west of the Dunedin airstrip.  NOGO sites - northern goshawk call playback sites scattered throughout the west-central portion of the FNFD and accessed by foot, vehicle, helicopter, and horses.  Prophet River - within the Prophet River drainage and accessed by the Alaska Hwy. 50-100 km south of Fort Nelson.

3.2 Breeding Range Delineation We generated distribution maps for each listed species with locations from recent surveys plotted over the previous ranges as reported by Godfrey (1986) and Enns and Siddle (1996).

3.3 Habitat Use and Relative Abundance We summarized the habitat use for each listed species from recent studies in the FNFD and common habitat attributes are presented in tabular fashion. The habitat used by listed species in the FNFD was compared to


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the habitat they used in other regions of the boreal forest. Densities of listed species were estimated from point count and transect data from the FRBC studies and compared to density estimates in the literature. Most of the density estimates come from eastern studies and provide a reasonable comparison between the relative abundance of listed species in northeastern BC to the eastern and central parts of their range.

4.0 Results 4.1 General The number of neotropical migrant songbirds1 recorded throughout the FNFD appeared to decrease the farther north and west studies were in the FNFD (Figure 2). The Prophet River study site in the southern portion of the FNFD had the most neotropical migrants (Savignac 1998) and the Smith River in the northwest portion of the FNFD had the least (Bennett et al. 1999).

30

27 20

21

Dunedin

25

Smith

No. of Species

35

22

No. of Sample Days

23

Smith Dunedin Liard NOGO Prophet

20 15 10

35 8 25 40 39

5

Prophet

NOGO

Lia rd

0

Study Area Figure 2. Number of neotropical migrant species recorded by study site (Prophet River data from Savignac 1998). Since 1996, 357 individual records of listed species have been made in the FNFD (Figure 3). These records account for approximately 80% of all records of listed species collected in the FNFD to date (S. Cannings, Pers. Comm.). The new records also represent predominantly new sites where the species have been recorded. Previous records were generally along the Alaska Highway, at provincial parks, and near the Fort Nelson airport. The Prophet River was the only site where all six listed species were recorded in the FNFD and it is the only site where BTNW, COWA, and PHVI have been recorded (Figure 3). BBWA, CAWA, and CMWA were all recorded at the Liard, NOGO and Dunedin sites whereas the CMWA was the only listed species to be recorded at the Smith River site. 1

We used the list of neotropical migrants used by Savignac (1998) to compare total numbers between studies. Only forest songbirds were considered (i.e. swallows, shorebirds, and other open habitat species are not included in the totals presented).


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No. of individuals recorded per study area

160 140 120 SMITH

100

DUNEDIN LIARD

80

NOGO PROPHET

60 40 20 0 BBWA

BTNW

CAWA

CMWA

COWA

PHVI

Species Figure 3. The number of listed songbird species recorded in the FNFD since 1996 by study area. All the studies found species using similar habitats to those described in the literature with the exception of the CAWA. Almost all of the records of CAWA since 1996 were in mature aspen dominated forests whereas in studies outside the FNFD, CAWA were frequently recorded in younger cut over areas (McLaren 1987). Mature and old forests appeared to be preferred by all listed species except the COWA and to a lesser extent PHVI, which used pole stage aspen (Savignac 1998). All listed species were generally restricted to valley bottom sites and mid slopes along major rivers except CMWA which were found in mid to upper elevations throughout the FNFD (Bennett and Enns 1996, Bennett 1999). There is a unique assemblage of western montane and eastern boreal forest bird species in the FNFD because it is bordered on the west by the Rocky Mountains and the east by the northern Alberta Plain. “Western” species such as western tanager (Piranga ludoviciana) (WETA), Townsend’s warbler (Dendroica townsendi) (TOWA), varied thrush (Ixoreus naevius) (VATH), and Hammond’s flycatcher (Epidonax oberholseri) (HAFL) were common and recorded in the same locations as “eastern” species such as BBWA, magnolia warbler (Dendroica magnolia) (MAWA), ovenbird (Seiurus aurocapillus) (OVEN), and rose-breasted grosbeak (Pheucticus ludovicianus) (RBGR) (Greenberg and Sterling 1998, Bennett and Enns 1996, Bennett et al. 1998, Savignac 1998, Bennett 1999). The FNFD is also uniquely situated at the southern extent of many arctic breeding species and the northern extent of many southern breeding species. For example we found evidence of breeding Pacific loons (Gavia pacifica) (PALO) and Arctic terns (Sterna paradisaea) (ARTE) in the same area as breeding pairs of black terns (Chlidonias niger) (BLTE) and soras (Porzana carolina) (SORA).

4.2 Bay-breasted warbler 4.2.1 Abundance/Population Status  Provincial Listing: Red


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 Conservation Data Centre Provincial Rank: S2B,SNZ - Imperiled because of extreme rarity or because of some factor(s) making it especially vulnerable to extinction.  Conservation Data Centre Global Rank: G5 - Secure, typically widespread and abundant.  COSEWIC: Not listed  BC Identified Wildlife: No BBWA were relatively common in their preferred habitat. The density of BBWA was the 3rd highest out of 20 species in the mature mixed riparian forest and 5th highest out of 31 species in the mature conifer riparian forest at the Liard River (Bennett and Enns 1996). Eastern North American populations have been demonstrated to fluctuate widely depending on spruce budworm (Choristoneura fumiferana) levels (Williams 1996). No long-term studies have confirmed that this phenomenon occurs in the western part of their range. A North American wide decline in BBWA populations has not been demonstrated, although forest harvesting and spraying of vast areas of forest to control for spruce budworms are anticipated to cause population declines.

4.2.2 Distribution BBWA breed across the boreal forests of Canada and northern New England with the bulk of the population thought to be in Ontario, Quebec, and the Maritime Provinces (Dunn and Garrett 1997). The breeding range extends from east-central and northeastern BC to the extreme southeastern Yukon, and across northeastern Alberta as far as western Newfoundland (Dunn and Garrett 1997) (Figure 4). BBWA winter from Costa Rica and Panama to northwest South America east of the Andes (Williams 1996, Dunn and Garrett 1997). The breeding distribution has been confirmed in the Yukon, as a BBWA nest site was found in the lower LaBiche River drainage in 1996 (Eckert 1998). Enns and Siddle (1996) also recorded secondary evidence of breeding northwest of Fort Nelson in 1992. Records since 1996 have expanded the range west by approximately 75 km (Figure 4). No nest sites have been located but males have been recorded defending territories and males and females have been seen carrying food to suspected nest sites.

4.2.3 Habitat Use Enns and Siddle (1996) proposed a BBWA habitat model of mixedwood stands dominated by tall, closed canopy large spruce, with aspen and birch also common in the canopy and a tall (1-2 m) shrubby understory of highbush cranberry (Viburnum opulus), red-osier dogwood (Cornus stolonifera), and green alder (Alnus crispa). All studies since then have found BBWA using similar habitat with the exception of balsam poplar also being associated with BBWA sites (Bennett and Enns 1996, Bennett 1999). It appears that the farther north and west BBWA are found in the FNFD, the more restricted they are to valley bottom and mid slope mature mixed forests. In the southern central portions of the FNFD, the BBWA has been found at numerous upland slope sites and does not appear to be restricted to large river valleys (Bennett et al. 1998, Savignac 1998). However, at the “Big Bend” on the Liard River and in the Dunedin River, BBWA were restricted to valley bottom and mid slope sites (Bennett and Enns 1996, Bennett 1999). Table 1 summarizes the BBWA breeding habitat attributes. year to year


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Figure 4. Recent records of bay-breasted warblers in the FNFD compared to their historic breeding range.


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Table 1. Summary of habitat attributes and site series associations for listed neotropical migrants in the Fort Nelson Forest District.


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4.3 Black-throated green warbler 4.3.1 Abundance/Population Status  Provincial Listing: Red  Conservation Data Centre Provincial Rank: S2B,SNZ - Imperiled because of extreme rarity or because of some factor(s) making it especially vulnerable to extinction.  Conservation Data Centre Global Rank: G5 - Secure, typically widespread and abundant.  COSEWIC: Not listed  BC Identified Wildlife: No The BTNW is likely a rare breeding bird in the FNFD. Both studies that recorded the BTNW in the FNFD were in the southern portion of the district and only nine records were made (MacNaughton 1995, Savignac 1998). BTNW are found in higher numbers in the Fort St. John and Dawson Creek Forest Districts (Merkens and Booth 1998, C. Siddle, Pers Comm.). Long-term declines and range contractions have occurred in Wisconsin, Michigan, and southern Ontario, but North American trends are confused by population fluctuations (Dunn and Garrett 1997). The greatest abundance of BTNW are thought to occur in Maine, Nova Scotia, and New Brunswick.

4.3.2 Distribution BTNW breed across the boreal forests of Canada from east-central BC and northern and central Alberta to Newfoundland (Dunn and Garrett 1997). The BTNW also breeds in central Minnesota and the Appalachian Mountains (Dunn and Garrett 1997). BTNW winter mainly in northeast Mexico south to Central America. The breeding distribution has been confirmed by MacNaughton (1995), Siddle (1992) and Enns and Siddle (1996) who, combined, have over 122 records of the BTNW in the Boreal Plains and Taiga ecosections around Fort St. John. Records since 1996 have expanded the range north by approximately 100 km (Figure 5). No nests have been located in BC (Campbell et al. 1999).

4.3.3 Habitat Use Enns and Siddle (1996) proposed a BTNW habitat model of tall mixedwood stands of spruce and poplar with mid-aged mid-canopy aspen (BWBS balsam poplar riparian habitat type). They also found BTNW in the same habitat used by OVEN. The stands tended to be mesic with relatively shrubby understories of highbush cranberry, prickly rose (Rosa acicularis), bunchberry (Corus canadensis), and fireweed (Epilobium angustifolium). The only study to find BTNW since 1996 was the Prophet River study. At the Prophet River, BTNW were found in a relatively closed mature mixed stand and a relatively open aspen dominated stand with a thick shrub layer (Savignac 1998). It appears that the BTNW is more restricted to old, valley bottom forests than the other listed warblers as it is rarely found in upslope sites (Savignac 1998, C. Siddle, Pers. Comm.). Table 1 summarizes the BTNW breeding habitat attributes.

4.4 Canada warbler 4.4.1 Abundance/Population Status  Provincial Listing: Blue  Conservation Data Centre Provincial Rank: S3S4B - Vulnerable to apparently secure (uncertain about exact status).  Conservation Data Centre Global Ranking: G5 - Secure, typically widespread and abundant.  COSEWIC: Not listed  BC Identified Wildlife: No


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Figure 5. Recent records of black-throated green warblers in the FNFD compared to their historic breeding range.


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CAWA were relatively common in most of the surveys and often one of the most common species in their preferred habitat. For example, at the Liard River study site, CAWA were the most abundant species in mature deciduous upslope forest. At the Prophet River, CAWA were only recorded twice, but all habitat types were not systematically surveyed (Savignac 1998). Sharp population declines have been noted in Pennsylvania due to fragmentation; however, it appears to be stable over much of its range (Dunn and Garrett 1997).

4.4.2 Distribution CAWA breed across the boreal forests of Canada from northeastern BC to Nova Scotia and south to central Alberta across to northeastern Ohio (Dunn and Garret 1997). They winter almost exclusively in South America east of the Andes in Columbia, Peru, Ecuador, and Venezuela (Dunn and Garret 1997). The breeding distribution has been confirmed in BC by Siddle (1992), Enns and Siddle (1996), Bennett and Enns (1996), Bennett et al. (1997), Savignac (1998) and Bennett (1999) who have recorded 141 CAWA in the Boreal Plains and Taiga ecosections between Fort St. John and the Yukon/BC border (Figure 6). Records since 1996 have expanded the range west by approximately 50 km (Figure 6). No nest sites have been located but evidence of breeding has been observed ( i.e. males and females carrying food, males defending territories). CAWA have also been recorded frequently in the southeastern portion of the Yukon along the Liard River (C. Machtans, Pers. Comm.).

4.4.3 Habitat Use Enns and Siddle (1996) proposed a CAWA habitat model of steep unstable slopes with thick undergrowth, often dominated by soopolallie (Sheperdia canadensis) and rose. Birch was the dominant tree cover and spruce, aspen, and balsam poplar were also present. Windthrow trees and debris were common. Almost all records of CAWA since 1996 have been in mature aspen stands with closed canopies, open mid stories (tree stems spaced widely), and dense understories often dominated by alder and highbush cranberry (Bennett and Enns 1996, Bennett et al. 1998, Savignac 1998, Bennett 1999). Two records along the Liard River were from young deciduous forest types (Bennett and Enns 1996). Other literature suggests that CAWA prefer riparian habitats and shrubs along streams (Dunn and Garrett 1997) but most of our records have been in upslope forests. These records suggest that CAWA require dense shrub habitat but can exploit both mature and young forest types depending on location and availability. Table 1 summarizes the CAWA breeding habitat attributes.

4.5 Cape May warbler 4.5.1 Abundance/Population Status  Provincial Listing: Red  Conservation Data Centre Provincial Rank: S2B,SNZ - Imperiled because of extreme rarity or because of some factor(s) making it especially vulnerable to extinction.  Conservation Data Centre Global Rank: G5 - Secure, typically widespread and abundant.  COSEWIC: Not listed  BC Identified Wildlife: No CMWA were relatively common in most of the surveys and often one of the most common species in their preferred habitat. For example, CMWA were the 4th most common bird recorded in the mature conifer habitat at the Dunedin airstrip, and the 7th most common in old coniferous habitat at the Smith River. Population status estimates are problematic for CMWA populations because they fluctuate more than most warblersdue to their reliance on spruce budworm populations (which are known to be very cyclic). Some local decreases and increases have been noted with no clear North American wide trend (Dunn and Garrett 1997, Baltz and Latta 1998). The cyclic nature of CMWA populations have only been confirmed in the eastern part of their range.


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Figure 6. Recent records of Canada warblers in the FNFD compared to their historic breeding range.


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4.5.2 Distribution CMWA breed across the boreal forests from southeastern Yukon and northeastern BC across Canada to southwestern Newfoundland (Dunn and Garrett 1997) and are generally thought to be more common in the eastern part of their range (Dunn and Garrett 1997). CMWA winter primarily in the Bahamas and islands in the western and southern Caribbean (Baltz and Latta 1998). The breeding distribution has been confirmed in the southeastern Yukon where CMWA were recorded along the LaBiche and Beaver Rivers (C. Machtans, Pers. Comm.). Their distribution was also confirmed in northeastern BC where they were recorded around Fort Nelson (Enns and Siddle 1996). Records since 1996 have expanded the range northwest by approximately 150 km (Figure 7). No nest sites have been located but males have been recorded defending territories and males and females have been seen carrying food to suspected nest sites (Bennett and Enns 1996, Bennett et al. 1998, Bennett 1999).

4.5.3 Habitat Use CMWA occupy mature to medium aged coniferous forests or bogs dominated by black and/or white spruce (Dunn and Garrett 1997, Baltz and Latta 1998). Enns and Siddle (1996) proposed a CMWA habitat model of white spruce in relatively dense tall stands on flat ground with an open mossy understory. Almost all records of CMWA since 1996 have been in mature black and/or white spruce stands with open moss dominated understories (Bennett and Enns 1996, Bennett et al. 1998, Savignac 1998, Bennett 1999). CMWA were found in young (40-80 years) to old (> 140 years) forests, but most of the sightings were in mature forest. Tall spruce trees protruding from the canopy were often used by males for singing perches. Table 1 summarizes the CMWA breeding habitat attributes.

4.6 Connecticut Warbler 4.6.1 Abundance/Population Status  Provincial Listing: Red  Conservation Data Centre Provincial Rank: S2B,SNZ - Imperiled because of extreme rarity or because of some factor(s) making it especially vulnerable to extinction.  Conservation Data Centre Global Ranking: G4 - Apparently secure, uncommon but not rare, and usually widespread. Possible cause for long-term concern.  COSEWIC: Not listed  BC Identified Wildlife: No The COWA is not a common species anywhere in its range (Dunn and Garrett 1997). There is some evidence it has declined since the 19th century, but it is unclear why since breeding and wintering habitat appear to be relatively secure (Cooper et al. 1997f, Dunn and Garrett 1997).

4.6.2 Distribution COWA breed across the boreal forests in Canada in a relatively narrow band from northeastern and eastcentral BC, central Alberta, to central Quebec (Dunn and Garrett 1997). It is generally uncommon and local over much of its range (Dunn and Garrett 1997). COWA wintering range is poorly understood but they are thought to winter entirely in South America in the Amazon region. The breeding distribution has been confirmed by Siddle (1992) and Enns and Siddle (1996), who recorded 26 COWA around Fort St. John. COWA are more abundant in the Dawson Creek and Fort St. John Forest Districts (Merkens and Booth 1998; C. Siddle, Pers. Comm.). Since 1996, COWA have only been recorded along the Prophet River in the FNFD which is a range expansion north by approximately 100 km (Savignac 1998) (Figure 8). No nest sites have been located but males have been recorded defending territories and males and females have been seen carrying food to suspected nest sites (Campbell et al. 1999).


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Figure 7. Recent records of Cape May warblers in the FNFD compared to their historic breeding range.


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Figure 8. Recent records of Connecticut warblers in the FNFD compared to their historic breeding range.


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4.6.3 Habitat Use Habitat varies widely throughout its range from wet conifer bogs to well drained deciduous woodlands (Dunn and Garret 1997). Enns and Siddle (1996) proposed a COWA habitat model of mature, well spaced aspen dominated forests on flat to gently sloping terrain with intermittent white spruce. The understory was well developed with a noticeable gap between the shrub layer and the canopy layer. Since 1996, COWA have only been recorded at the Prophet River (Savignac 1998). All records of COWA at the Prophet River were in immature aspen stands (Savignac 1998). Table 1 summarizes the COWA breeding habitat attributes.

4.7 Philadelphia Vireo 4.7.1 Abundance/Population Status  Provincial Listing: Blue  Conservation Data Centre Provincial Rank: S3S4B - Vulnerable to apparently secure (uncertain about exact status).  Conservation Data Centre Global Ranking: G5 - Secure, typically widespread and abundant.  COSEWIC: Not listed  BC Identified Wildlife: No PHVI appear to be relatively rare and locally distributed, and their distribution is likely associated with the presence of adequate deciduous forests (Campbell et al. 1997). They may be vulnerable to logging of northeastern deciduous forests but their ability to use second-growth forests likely makes them less vulnerable than other northeastern songbirds (Cooper et al. 1994b). Non-significant increases and decreases in populations have been noted in Canada and the USA and their habitat appears to be relatively secure (Moskoff and Robinson 1996).

4.7.2 Distribution PHVI breed across the boreal forests Canada from southeastern Yukon and northeastern BC to southwestern Newfoundland (Godfrey 1986, Campbell et al. 1997). They are generally uncommon and local over much of their range. PHVI winter from Guatemala south to central Panama (Ehrlich et al. 1988). Breeding of PHVI has been confirmed by Enns and Siddle (1996) who recorded six PHVI around Fort St. John and Fort Nelson, and CWS who recorded PHVI in southeastern Yukon (C. Machtans, Pers. Comm.). Since 1996, PHVI have only been recorded in the Prophet River (Savignac 1998) which is within their previously defined range (Enns and Siddle 1996) (Figure 9). Five nest sites have been located in stands of trembling aspen (4) and balsam poplar (1) (Campbell et al. 1997).

4.7.3 Habitat Use PHVI typically use tall, young aspen or balsam poplar stands with 80-100% canopy closure (Campbell et al. 1997). Some mixed aspen and spruce forests are also used and both old-growth and second-growth stands are used but second-growth stands are probably preferred (Campbell et al. 1997). Enns and Siddle (1996) propose a PHVI habitat model of dense, rapidly growing young aspen (~20 yrs. old), with lots of branches in the mid to lower canopy, and a 80-100% canopy closure. Associated understory species included Indian paintbrush (Castilleja miniata), fireweed, highbush cranberry, alder, willow sp. (Salix sp.), and clover (Trifolium hybridum). Since 1996, PHVI have only been recorded at the Prophet River (Savignac 1998). All records of PHVI at the Prophet River were at the edge of old forests and old clearcuts dominated by deciduous trees (Savignac 1998). Table 1 summarizes the PHVI breeding habitat attributes.


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Figure 9. Recent records of Philadelphia vireos in the FNFD compared to their historic breeding range.


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5.0 Discussion 5.1 Status and Distribution CMWA, CAWA, and BBWA appear to be widely distributed in the FNFD and common in their preferred habitat. The CMWA probably has the widest distribution throughout the district and within individual valleys, as it utilizes valley bottom to upper elevations more readily than BBWA and CAWA. BTNW and COWA are rare in the district and appear to have a much more restricted and patchy distribution. They are mainly restricted to the southern and eastern portions of the district. PHVI appear to have a similar distribution to BTNW and COWA as they are rare in the FNFD and sporadically distributed. However, PHVI have been recorded in southeastern Yukon along the LaBiche River which enters the Liard River approximately 25 km northwest of the “Big Bend” study site (C. Machtans, Pers. Comm.). This suggests that PHVI occur throughout the FNFD at least as far east as Fort Nelson and north to the Yukon border. As Campbell et al. (1997) noted, PHVI are restricted to areas with adequate young to mature deciduous forests. The songs of the the PHVI and red-eyed vireos (REVI) are very similar, and the PHVI may even mimic the REVI, which also makes it difficult to determine the true distribution of PHVI. It is unknown whether populations of any of the listed species are declining throughout North America or specifically in BC because there are limited data, a high degree of variability in population levels from year to year, and ranges contract and expand periodically (Cooper et al. 1997a-f). However, all the listed species utilize young to mature forest habitats to some degree and these habitats are being harvested at an increasing rate in the FNFD. Based on the last three years of inventory work, a review of the status of listed neotropical migrants in northeastern BC is necessary to update the current designations. We believe BBWA, and CAWA are likely still at risk because they appear to utilize lower elevation habitats along major river systems which have already been harvested extensively. BTNW, COWA, and PHVI are also likely still at risk because of their rarity and restricted, patchy distribution in the district. CMWA appear to be the least at risk because they are more widely distributed throughout the FNFD.

5.2 Abundance and Habitat Use Many of the species found in the study areas, including all the red and blue listed species, have a breeding distribution that extends from the hardwood forests of eastern North America through the boreal forest to terminate in northwestern British Columbia and the southern Yukon (Godfrey 1986, Campbell et al. 1997, Dunn and Garrett 1997). The designation of these species as "eastern" has given rise to the idea that the breeding heartland of such species is in the eastern provinces of Canada with numbers diminishing westwards until finally a scattering of isolated pairs are found at the western terminus of the range. The listed status of a number of these species in northeastern BC, together with published range maps that show them barely reaching the province, appear to have supported this contention. To test this idea, six neotropical migrant warbler species were selected and their breeding densities in the present study areas were compared to published breeding densities elsewhere in Canada and northeastern USA. Three of these species, CMWA, BBWA and Tennessee warbler (Vermivora peregrina) (TEWA), are spruce budworm specialists. The other three, CAWA, MAWA,and OVEN, are more general insectivores which exploit a wide range of invertebrate food, and have populations that tend to be stable over long periods. The breeding ranges of these six species terminate in northern BC or adjacent southern Yukon with the exception of the Tennessee warbler, which extends across most of BC to the west coast (Dunn and Garrett 1997). The scale of the studies considered and to a certain extent the methodologies vary considerably but do allow for broad comparisons of breeding densities across the northern range of each species. To facilitate comparison, all densities have been normalized to pairs/ha, a singing male bird being considered to represent a pair, and a point count circle of 50m and a transect of 100m considered approximately equivalent to an hectare. The density estimate results should be interpreted with caution since we are comparing relatively short-term studies in the FNFD with long-term studies in the east and the survey techniques and objectives varied. Some of the density estimates we calculated are also based on small samples (< 500 m of habitat or limited number of point counts). Also, populations of the species in


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question, especially the spruce budworm specialists, are know to fluctuate widely and asynchronously over their geographic range. The lack of site specific spruce budworm levels at the study sites complicates these comparisons. Some budworm “hotspots” have been noted by MOF along major rivers in the FNFD and east of Fort Nelson since 1996 (R. Hodgkinson, Pers. Comm.) and these areas may have influenced some of our results.

Area defoliated (ha)

Spruce budworm specialists The three species in this group have populations that expand during outbreaks of spruce budworm and contract or even disappear in periods between outbreaks. This makes comparison of numbers more difficult, especially when comparing short and long-term studies. Although budworm was widely encountered in the "Big Bend" study area (Bennett and Enns 1996) there was no evidence of infestation and forest monitoring data indicate that the last several years were low budworm years regionally (Taylor 1996, Tayor 1997, R. Hodgkinson, Pers. Comm.) (Figure 10).

450000 400000 350000 300000 250000 200000 150000 100000 50000 0 1989

1990

1991

1992

1993

1994

1995

1996

Year Figure 10. Number of ha of forest defoliated by the spruce budworm in the FNFD: 1989-1996 (Taylor 1996, Taylor 1997). Reported densities of CMWA in Ontario ranged from 0.20-1.48 pairs/ha during spruce budworm outbreaks to 0-0.34 pairs/ha in non-budworm years (Figure 11, Appendix I). Reported densities in Maine and Quebec are 0.30 and 0.20 respectively in infestation years. Studies in northeastern Alberta suggest that the bird is rare to absent and Alberta breeding bird atlas data (Semenchuck, 1992) indicate a very sparse distribution across northern Alberta. Surveys in the Liard River valley of the NWT in 1994 demonstrated densities of up to 0.18 and 0.21 in white spruce habitats. Mature conifers yielded up to 0.11 pairs/ha during the 1997 "Big Bend" study and a similar 0.19 close to the presently established western extremity of the species' range at the Smith River in 1998. A limited area survey at the Dunedin River in 1998 produced a density of 0.51, comparable to average budworm outbreak densities in Ontario, although there was no evidence of infestation in the area. It therefore appears that densities of this species in its preferred mature conifer habitat are broadly similar across its range and that northeastern BC may contain a significant breeding population of CMWA.


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Density (pairs/ha)


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1.80 1.60 1.40

Smith

1.20

Dunedin

1.00

Liard

0.80

Alberta

0.60

E. Boreal

0.40 0.20 0.00 BBWA

CMWA

TEWA

Species Figure 11. Comparison of the densities (pairs/ha) of budworm specialists. As with the CMWA, many of the published densities of BBWA are from the east during budworm outbreaks (Appendix I). Reported BBWA densities as high as 4 pairs/ha were recorded in New Brunswick and 1.20-2.30 pairs/ha in Ontario during budworm years. The highest density at the "Big Bend” on the Liard River was 0.89 in mature mixed riparian habitats, a figure similar to the low density range of Ontario budworm years and higher than the "average" density for the boreal forest (Francis and Lumbis 1980) (Figure 11). Again it appears that the breeding density of this species in suitable habitat is comparable to other parts of its range, even close to its western boundary. Long-term studies in Ontario show almost ten-fold fluctuations in TEWA populations (Appendix I). An average breeding density of 1.60 has been calculated for the boreal forest in Ontario and eastward and 0.49 for Manitoba westward (Rimmer and McFarland 1998). The Liard River in the NWT has densities close to the western average (0.59, 0.45) while those from the Liard in BC are close to or exceed the eastern average (1.55, 1.90) in what appears to be a non-budworm year (Figure 11). Even farther west, densities were as high as 0.90 in the Smith area in 1988, considerably higher than the western average. Overall, the northern BC population of TEWA (although in this instance not at the edge of its range) appears to be more comparable in its densities to the eastern as opposed to the central part of its range. Generalist insectivores The CAWA is a shrub-nesting species that appears to benefit from shrub growth associated with natural clearing (blowdown, burns) and logging. In Ontario, densities of 1.28 pairs/ha were associated with mixedwood cutover forest (Appendix I). In the NWT, data suggest low densities comparable to unlogged forest in Ontario, but maximum densities on the "Big Bend" in mature upslope deciduous forest (0.58 pairs/ha) were almost identical to those in a mixed forest in northeastern Alberta (0.56 pairs/ha) (Figure 12). Although the comparative data for this species are not as extensive as for the others, it suggests that breeding densities of CAWA can be as high at the range margin in BC as in the central part of their range.


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Density (pairs/ha)

1.40 1.20 Smith

1.00

Dunedin 0.80

Liard

0.60

Alberta E. Boreal

0.40 0.20 0.00 CAWA

MAWA

OVEN

Species Figure 12. Comparison of the densities (pairs/ha) of non-budworm specialists. Studies in New York State suggest that MAWA has markedly declined from 0.71 (1930-1931) to 0.21(1983-1985) (Hall 1994) (Appendix I). The earlier figure from New York State is close to the highest densities recorded on the "Big Bend" of 0.95 and 0.65 pairs/ha in mature conifer riparian and mature mixed upslope habitat respectively. The “Big Bend” densities are also among the highest breeding densities found anywhere in its range (Appendix I). Again, proximity to the western end of its range does not appear to produce lower densities in suitable habitats as illustrated by comparatively high densities of up to 0.49 pairs/ha in the Smith River study site. The OVEN is "area dependent" on its breeding grounds, requiring large tracts of contiguous forest to breed successfully (Robbins et al. 1989). As a result many breeding populations in eastern North America have experienced significant declines (Robbins et al. 1989). A study in the Prince Albert Model Forest, Saskatchewan (Hobson and Bayne 1997) suggests that the area required for a minimum viable population to exist in the area was 77 ha of contiguous forest, rising to 260 ha in forest fragments. The density of 1.23 pairs/ha recorded in mature deciduous riparian forest at the "Big Bend" in 1997 is similar to the 1.38 pairs/ha recorded in unfragmented aspen forest in northeastern Alberta and may be close to maximum average values (Appendix I, Figure 12). Territory size varies according to food availability and the distribution of habitats, but a study in Ontario found territory ranged from 0.61 to 1.60 pairs/ha (Van Horn and Donovan 1994). Breeding densities on the "Big Bend" appear to be among the highest in the species' boreal forest range even though the area is close to the western margin of the range. Densities up to 0.50 pairs/ha were found even at the present known extremity of the species' range at the Smith River (Appendix I, Figure 12). Each of these warbler species appears to have surprisingly high breeding densities in suitable habitat in northeastern BC, even, in some cases, beyond the previously known western limit of the species distribution. In general the densities are comparable to or are higher than those in the central and eastern parts of its range. As most individuals of these species migrate to the area from the east or southeast they must travel considerably greater distances than their eastern counterparts to reach their breeding grounds. Rather than being considered marginal to their breeding range, it appears that much of the habitat in northeastern BC is optimal for their breeding requirements and birds may be being rewarded for the extra expenditure of energy on migration by higher breeding success. Much of the boreal forest in the FNFD has relative topographic complexity, extensive riparian forest habitat associated with large rivers, coarse textured well drained soils, high precipitation, and high latitude (giving


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long summer daylight hours). These factors lead to increased forest productivity compared to much of the boreal forest (Gray 1995), especially much of Alberta, where poor soil drainage and thick moss layers severely impede tree growth (D. Patterson, Pers. Comm.). These factors likely lead to an overall increased level of ecosystem productivity and increased levels of insect food. Also important is the fact that much of the area is presently intact with minimal fragmentation of habitat compared to eastern boreal forests. The number of neotropical migrant songbirds found in each study site likely does not represent the total number present as all the study sites have not been fully inventoried and the number of days spent in each study site varied considerably. However, these data do suggest that the diversity of neotropical migrants decreases from south to north and likely east to west in the FNFD.

6.0 Management Recommendations/Future Research Studies to date in the FNFD have focused primarily on reconnaissance level inventories with a secondary objective of developing habitat models for listed species. Complete distribution maps will take many years to complete as access is severely limited during the summer months. However, habitat models for the listed species that were developed from other studies appear to be relatively accurate. The following recommendations are based on the premise that harvesting will continue before further surveys help to define species distributions and strengthen current habitat models. Management Recommendations  Maintain connectivity of mature forest fragments and maximize the size of mature forest fragments whenever possible to mitigate the effects of forest fragmentation (Schmiegelow, et al 1997).  Portions of the remaining mature conifer, mixed, and deciduous riparian and mid slope habitat should be maintained in reserves until further studies determine the impact of harvesting these stands on populations of listed species (especially BBWA and CAWA).  Maintenance of mixedwood stands throughout forestry rotations should be encouraged by use of group shelterwood silviculture systems.  Habitat suitability maps should be created for all listed species for the entire Fort Nelson Forest District based on recently proposed habitat associations. Areas mapped as highly suitable should be deferred from harvesting whenever possible until a review of the status of northeastern warblers is completed. 1:50,000 TEM may be suitable but should involve some ground truthing.  Specific guidelines need to be established for maintaining the diverse bird species assemblage found in the FNFD and the listed species can be used as indicators of the guidelines’ success. Future Research Evidence is mounting that some listed warbler species are dependent on mature forested habitat for breeding and rearing young, although very little inventory work has been completed in northeastern BC compared to other portions of the province. Future research should focus on the following:  The status of listed species could be reviewed by the Conservation Data Centre now that significant progress has been made in defining the distribution and abundance of many of the listed species. These status reviews will help guide any future research.  More broad scale inventories need to be conducted in the FNFD to accurately map the distributions of listed and non-listed species. A sampling program should be based on habitat suitability mapping and visiting as many unsampled areas as possible.


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 Detailed nest searches should also be conducted later in the season (end of June, first half of July) to confirm successful breeding of listed species  Nest productivity in the FNFD needs to be compared with eastern populations to test hypothesis that forest productivity is relatively high compared to other parts of the boreal forest.  Studies should begin to look at avian responses to different levels of harvesting. Some mature stands should be harvested in an experimental fashion (i.e. adaptive management) to test the effects of harvesting on listed species. Pre-treatment data should be collected and the study sites should be monitored for several years to account for possible lag effects. Current mixedwood trial blocks could provide excellent study locations and could help to reduce costs of the experiment.  Future inventories should collect baseline information on the levels of spruce budworm and other important forest insects to correlate bird densities with prey availability. This could be done in cooperation with MOF. Suitable habitat may not be used by some of the listed species if prey populations are low (Cooper et al. 1997a,d) but this has not been confirmed in western populations.  A long-term monitoring program should be established to help determine the status of listed and unlisted species. The monitoring program should be established in accordance with existing RIC and CWS guidelines.

7.0 Conclusion Distribution and Abundance  BTNW and COWA are relatively rare and likely restricted to the southern portion of the FNFD.  PHVI are relatively rare and sporadically distributed throughout eastern portion of FNFD as far north as southeastern Yukon.  BBWA, CAWA, and CMWA are all common in their preferred habitat.  BBWA and CAWA are likely more restricted to valley bottom and mid slope locations and their range may not extend as far as the Smith River.  CMWA are more widely distributed than other listed species and its breeding range likely extends as far west as Watson Lake, Yukon. Habitat Use/Status  The habitats used by listed species in the FNFD were similar to those reported in the literature with BBWA, BTNW, CAWA, and CMWA using mature deciduous to coniferous dominated forests and COWA and PHVI using young to mature deciduous dominated forests.  None of the listed species has shown a significant decline across North America but all are susceptible because of a dependence on mature forests (i.e. BBWA, BTNW, CAWA, CMWA) and/or a relatively localized distribution in northeastern BC (i.e. BTNW, COWA, PHVI) Uniqueness of the Fort Nelson Forest District


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 The area has a unique combination of "eastern" species and "western" species characteristic of the western cordillera and also marks the southern limit of such northern species as Arctic Tern and Pacific Loon. Such avifauna and their habitat should be protected.  Densities of the common listed species (BBWA, CAW, CMWA) and several other neotropical migrants were similar to the densities reported from the eastern and central parts of their range. This suggests that the FNFD provides optimal habitat for neotropical migrants despite being at the western extent of their range.


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8.0 Literature Cited Armstrong E. R. 1987. Ovenbird. Pp. 404-405 in Atlas of the Breeding Birds of Ontario (M.D. Cadman, P.F.J. Eagles, and F.M. Helleiner, eds.). Univ. of Waterloo Press, Waterloo. ON. Baird T. H. 1990. Changes in breeding bird populations between 1930 and 1985 in the Quaker Run Valley of Allegeny State Park. NY State Mus. Bull. No.447. Baltz, M.E. and S.C. Latta. 1998. Cape May Warbler (Dendroica tigrina). In The Birds of North America, no. 332 (A. Poole and F. Gill, eds.). The Birds of North America Inc., Philadelphia, PA. Bennett, S. 1999. Fort Nelson Forest Bird Inventory, 1998: Smith and Dunedin Drainages. Unpublished report prepared for Ministry of Environment, Lands and Parks, Fort St. John, B.C. Bennett, S. and K. Enns. 1996. A Bird Inventory of the Boreal White and Black Spruce Biogeoclimatic Zone near the "Big Bend" of the Liard River. Unpublished report prepared for Ministry of Environment, Lands and Parks, Habitat Protection Branch, Fort St.John, British Columbia Bennett, S., P. Sherrington, and W. Schaffer. 1998. Northern goshawk and diurnal raptor inventory of the Fort Nelson Forest District. Unpublished report prepared for Ministry of Environment, Lands and Parks, Habitat Protection Branch, Fort St.John, British Columbia Brittingham, M.C. and S.A. Temple. 1983. Have cowbirds caused forest songbirds to decline? Bioscience 33: 31-35. B.C. Ministry of Environment, Lands and Parks. 1998. Red and blue lists for terrestrial vertebrates. Wildlife Branch, Victoria, B.C. Bunnell, F.L. 1998. Time and space without Einstein: how do we distribute our treatments. Ecoforestry. Winter 1998. Campbell, R.W., N.K. Dawe, I. McTaggart-Cowan, J.M. Cooper, G.W. Kaiser, M.C.E. McNall, and G.E. Smith. 1997. The Birds of British Columbia. Vol. III. Passerines: Flycatchers through vireos. Royal British Columbia Museum, Victoria, BC. Campbell, R.W., N.K. Dawe, I. McTaggart-Cowan, J.M. Cooper, G.W. Kaiser, M.C.E. McNall, and G.E. Smith. 1999. DRAFT: The Birds of British Columbia. Vol. IV. Passerines: Wood warblers through Old World finches. Royal British Columbia Museum, Victoria, BC. Cannings, S. 1999. Program Zoologist, Conservation Data Centre, Victoria, BC. Pers. Comm. Cooper, J., K. Enns, and M. Shepard. 1997a. Status of the black-throated green warbler (Dendroica virens) in British Columbia. WR-80. Wildl. Br., MELP, Victoria, BC. Cooper, J., K. Enns, and M. Shepard. 1997b. Status report on the Philadelphia vireo (Vireo philadelphicus) in British Columbia. WR-84. Wildl. Br., MELP, Victoria, BC. Cooper, J., K. Enns, and M. Shepard. 1997c. Status of the bay-breasted warbler (Dendroica castanea) in British Columbia. WR-79. Wildl. Br., MELP, Victoria, BC. Cooper, J., K. Enns, and M. Shepard. 1997d. Status of the Cape May warbler (Dendroica tigrina) in British Columbia. WR-82. Wildl. Br., MELP, Victoria, BC.


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Cooper, J., K. Enns, and M. Shepard. 1997e. Status of the Canada warbler (Wilsonia canadensis) in British Columbia. WR-81. Wildl. Br., MELP, Victoria, BC. Cooper, J., K. Enns, and M. Shepard. 1997f. Status of the Connecticut warbler (Oporornis agilis) in British Columbia. WR-83. Wildl. Br., MELP, Victoria, BC. Demarchi, D. 1990. Ecoprovinces of British Columbia: A Synopsis. B.C. Ministry of Environment, Wildlife Branch. Victoria, B.C. Dunn, J.L. and K.L. Garrett. 1997. A field guide to warblers of North America. Peterson Field Guides, Houghton Mifflin Co., New York. Ehrlich, P.R., D.S. Dobkin, and D. Wheye. 1988. The Birder’s Handbook: A Field Guide to the Natural History of North American Birds. Simons and Schuster, New York. Eckert, C.D. 1998. DRAFT: Forest bird communities of the La Biche and Beaver River Valleys, Yukon. Technical Report Series. CWS, Pacific and Yukon Region, BC. Enns, K. and C. Siddle. 1996. The distribution, abundance and habitat requirements of selected passerine birds of the boreal and taiga plains of British Columbia. Wildlife Working Report No. WR-76. Flather, C. and J. Sauer. 1996. Using landscape ecology to test hypotheses about large-scale abundance patterns in migratory birds. Ecology 77 (1): 28-35. Francis, J. and K. Lumbis. 1980. Habitat Relationships and Management of Terrestrial Birds in Northeastern Alberta. Prep. For the Alberta Oil Sands Environmental Research Program by Canadian Wildlife Service. AOSERP Report 78. 365 pp. Godfrey, W. 1986. The birds of Canada, revised edition. Ottawa: National Museums of Canada. 595 p. Gray, S. 1995. A descriptive forest inventory of Canada’s forest regions. Information Rep. PI-X-122. Petawawa National Forest Institute, Canadian Forest Service. Greenberg R. and J. Sterling. 1998. Summary of Breeding Birds Found in Liard Valley Forests. Unpublished report, Smithsonian Migratory Bird Center. Hall G. A. 1994. Magnolia Warbler (Dendroica magnolia). In The Birds of North America, no. 136 (A. Poole and F. Gill, eds.). The Birds of North America Inc., Philadelphia, PA. Hobson K. A. and Bayne E. M. 1997. Prince Albert Model Forest Final Report, Presented to the Prince Albert Model Forest Association, May 1, 1997 Hodgkinson, R. 1999. Regional Forest Entomologist, Ministry of Forests, Prince George, BC. Pers. Comm. Kendeigh S. C. 1947. Bird population studies in the coniferous forest biome during a spruce budworm outbreak. Ontario Dept. Lands Forest, Biol. Bull. 1: 1-100. Kerlinger, P. and C. Doremus. 1981. Habitat disturbance and the decline of dominant avian species in pine barrens of the northeastern United States. Am. Birds. 35: 16-20. LRMP. 1997. Fort Nelson Land and Resource Management Plan. October 1997. McLaren P. L. 1987. Canada Warbler. Pp. 422-423 in Atlas of the Breeding Birds of Ontario (M.D.Cadman, P.F.J.Eagles, and F.M. Helleiner, eds.). Univ. of Waterloo Press, Waterloo. ON.


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Machtans, C. 1998. Biologist, Western Arctic Habitat Program, Canadian Wildlife Service, Yellowknife, Yukon. Pers. Comm. MacNaughton, C.J. 1995. The effects of prescribed burning on songbirds in the Tuchodi-Gathto Region of British Columbia. Prepared for the Wildlife Branch of the Ministry of Environment, Lands and Parks, Victoria, BC. Martin N. D. 1960. An analysis of bird populations in relation to forest succession in Algonquin Provincial Park, Ontario. Ecology 41: 126-140. Meidinger, D., and J. Pojar, Editors. 1991. Ecosystems of British Columbia. Research Branch, Ministry of Forests, British Columbia. Merkens, M. and B. Booth. 1998. Moniotring changes in wildlife diversity during operational hardwood harvesting: Aspen clearcutting in the Dawson Creek Forest District (1992-1997). Unpublished report prepared by PAW Research Services, Burnaby, BC, for Ministry of Environment, Lands and Parks, Victoria, BC. Ministry of Forests and Ministry of Environment, Lands and Parks. 1995. Forest Practices Code of British Columbia: Biodiversity Guidebook, September 1995. Morris R. F., Cheshire W. F., Miller C. A., and D.G. Mott. 1958. The numerical response of avian and mammalian predators during a gradation of the spruce budworm. Ecology 39: 497-494. Morse D.H. 1978. Populations of Bay-breasted and Cape May Warblers during an outbreak of the spruce budworm. Wilson Bull. 90:404-413. Morse D. H. 1980. Foraging and coexistence of spruce-woods warblers, Living Bird 18: 7-25. Moskoff, W. and S. Robinson. 1996. Philadelphia vireo (Vireo philadelphicus). In The Birds of North America, no. 214 (A. Poole and F. Gill, eds.). The Birds of North America Inc., Philadelphia, PA. Niemi, G., J. Hanowski, P. Helle, R. Howe, M. Mönkkönen, L. Venier, and D. Welsh. 1998. Ecological sustainability of birds in boreal forests. Conservation Ecology [online] 2(2): 17. Patterson, D. 1999. Forest Manager, Forest Management Division, Dept. of Environmental Protection, Edmonton, Alberta. Pers. Comm. Pastor, J., S. Light, and L. Sovell. 1998. Sustainability and resilience in boreal regions: sources and consequences of variability. Conservation Ecology [online] 2(2): 16. Robbins C. S., Sauer J. R., Greenberg R., and S. Droege. 1989. Population declines in North American birds that migrate to the Neotropics. Proc. Natl. ACAD. Sci. 86:7658-7662. Rimmer C. C. and K. P. McFarland. 1998. Tennessee Warbler (Vermivora peregrina). In The Birds of North America, no. 350 (A. Poole and F. Gill, eds.). The Birds of North America Inc., Philadelphia, PA. Sanders, C. J. 1970. Populations of breeding birds in the spruce-fir forests of northwestern Ontario. Can Field Nat. 84: 131-135. Savignac, C. 1998. Songbird diversity and cavity-nesting bird habitat in the Prophet Territory of northeastern British Columbia, 1998. Unpublished report submitted to Ministry of Environment, Lands and Parks, Fort St. John, BC.


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Schmiegelow, F.K.A., C.S. Machtans and S.J. Hannon. 1997. Are boreal birds resilient to forest fragmentation? An experimental study of short-term community responses. Ecology 78(6): 1914-1932. Semenchuck G. P. 1992. The Atlas of Breeding Birds of Alberta. Federation of Alberta Naturalists, Edmonton. Siddle, C. 1999. Bird researcher, Vernon, BC. Pers. Comm. Siddle, C. 1992. The declining populations of warblers in northeastern BC. In S. Rautio, ed.. 1992. Community Action for endangered species: a public symposium on BC’s threatened and endangered species and their habitat. Vancouver, BC. September 28-29, 1991. Speirs J. M. 1949. The relation of DDT spraying to the vertebrate life of the forest. In Forest spraying and some effects of DDT. Ont. Dept. Lands, For. Div. Res. Biol. Bull. 2: 141-158. Stewart R. E. and J. W. Aldrich. 1952. Ecological studies of breeding bird populations in northern Maine. Ecology 33:226-238. Taylor, S. 1996. Defoliator and beetle conditions in the Fort Nelson Forest District for 1996. Forest Health Note # 2. Ministry of Forests, Prince George Forest Region. Taylor, S. 1997. Bark beetle an other insect attack levels for 1996. Forest Health Note # 3. Ministry of Forests, Prince George Forest Region. Thorp, M. 1999. Operations Manager. Ministry of Forests, Fort Nelson, BC. Pers. Comm. Van Horn M. A. and T. Donovan. 1994. Ovenbird (Seiurus auricapillus). In The Birds of North America, no. 88 (A. Poole and F. Gill, eds.). The Birds of North America Inc., Philadelphia, PA. Welsh, D. A. 1987. Cape May Warbler. Pp. 376-377 in Atlas of the Breeding Birds of Ontario (M.D.Cadman, P.F.J.Eagles, and F.M. Helleiner, eds.). Univ. of Waterloo Press, Waterloo. ON. Welsh D. A. and D. R. Fillman. 1980. The impact of forest cutting on boreal bird populations. Amer. Birds. 34: 84-94.

Williams, J. M. 1996. Bay-breasted Warbler (Dendroica castanea ). In The Birds of North America, no. 206 (A. Poole and F. Gill, eds.). The Birds of North America Inc., Philadelphia, PA.


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Appendix I. Summary of densities estimates for spruce budworm specialists (CMWA, BBWA, and TEWA) and nonspruce budworm specialists (OVEN, CAWA, and MAWA) from eastern boreal forests and FNFD.


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