Changes in the non-breeding distribution of Continental Black-tailed Godwits Limosa limosa limosa over 50 years: a synthesis of surveys PEDRO M. LOURENÇO1 & THEUNIS PIERSMA1,2 1Animal
Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands.
[email protected] 2Department of Marine Ecology, Royal Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands
Lourenço, P.M. & Piersma, T. 2008. Changes in the non-breeding distribution of Continental Black-tailed Godwits Limosa limosa limosa over 50 years: a synthesis of surveys. Wader Study Group Bull. 115(2): 91–97. Keywords: Black-tailed Godwit, Limosa limosa limosa, population size, population trend, winter distribution, spring migration Over the years a large body of information as been gathered regarding the migratory and wintering distribution of Black-tailed Godwits Limosa limosa. Much of this information is only available in the so-called “grey” literature. Here we present a summary of non-breeding count data for the continental race L. l. limosa covering the last fifty years. We suggest that there have been important changes in the winter and spring-staging distribution and numbers of this now threatened population. The winter distribution covers a wide area from Senegal and Guinea-Bissau in the west, through Mali and Chad and extends into the Middle East as far as Iran. During spring, the most important staging sites are around the Mediterranean basin, with key areas in Iberia and France. Throughout the range, numbers have changed over time. Today, areas in West Africa, like Senegal, Morocco and, to some extent, Guinea-Bissau have much lower numbers of godwits than 20 years ago, whereas in Mali, Chad and north Cameroon numbers have remained more or less stable. Larger numbers of godwits now occur in southern Europe, Portugal and Spain; but the French wetlands have lost some of their past importance. researchers in other areas. Therefore we acknowledge that the data we present are biased towards Western Europe and the large number of counts that have been carried out by European ornithologists during expeditions to the many different countries mentioned. Nevertheless we consider that it is unlikely that any major source of relevant data has been overlooked. Table 1 shows the national origin of most of the data sources used. Counts were categorised as “winter” if they were carried out during Nov–Jan and as “spring migration” if they were carried out in Feb–Mar. However, our definition of “winter” is likely to include the early part of the northward migration, which frequently starts in mid December (Kuiper et al. 2006). January is the month chosen for the “midwinter” counts organized by Wetlands International (Delany et al. 1999, Gilissen et al. 2002) and this is the time of year for which most “wintering” data are available. However, January counts for Black-tailed Godwits in Morocco, Tunisia and the Iberian Peninsula very likely include birds already on northward migration. In order to present the results concisely and clearly, we summarise the counts for each geographical area by giving the mean and range for each decade.
INTRODUCTION The Black-tailed Godwit Limosa limosa is a distinct and enigmatic shorebird. The nominate subspecies L. l. limosa, which we here describe as the Continental Black-tailed Godwit (distinct from the Icelandic Black-tailed Godwit L. l. islandica, and the Asian Black-tailed Godwit L. l. melanuroides), comes as close to an endemic shorebird taxon as NW Europe is likely to have. As it breeds close to humans, the recent major population decline that has occurred in the rapidly changing agricultural environment of Europe has aroused considerable interest and concern (Gill et al. 2007). This, in turn, has inspired many investigations on the breeding grounds, but also in winter and staging sites. As so often with ecological issues that have a high public profile, much of the resulting literature been of the “grey” variety (reports and papers in regional journals difficult to access) (Beintema et al. 1995, Piersma 1986, Verstrael 1987). Here we have gathered non-breeding count data from a number of sources, particularly from the grey literature but also from refereed papers. This information has yielded a picture of patchy abundance and distribution of Black-tailed Godwits in West Africa, the Middle East and around the Mediterranean covering over 50 years. We hope that this summary, and its indication that considerable change has occurred over the last half century, will be helpful in giving context to future studies of Continental Black-tailed Godwits.
RESULTS The non-breeding distribution of the Continental Black-tailed Godwit ranges from West Africa (Altenburg & van der Kamp 1985, Kuiper et al. 2006, Trolliet & Fouquet 2004) through central and north-eastern Africa, and through the Arabian Peninsula and Iran well into Asia (Delany et al. 1999, Gilissen et al. 2002, Meininger & Atta 1994). There are also reports of large flocks in the Indian sub-continent (Delany &
METHODS This review is limited to data available through libraries in the Netherlands and Portugal and by contacting a few 91
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Wader Study Group Bulletin 115 (2) 2008
decrease. In Italy, spring numbers seem to have increased in the last few decades, but the data are scarce.
Table 1. Countries in which sources of count data on Continental Black-tailed Godwits were published. Country
Number of references
The Netherlands
27
DISCUSSION
France
12
Portugal
10
Although these data on winter and spring numbers and distribution of the Continental Black-tailed Godwit encompass a huge observation effort over fifty years, it is a very patchy and incomplete picture. A lack of godwit observations in a particular country and year might simply mean that nobody made the effort to count the birds. A good example is the apparent absence of godwits in Guinea-Bissau in the 1990s, which was a time when political unrest made ornithological work impossible. Nevertheless there are quite a few important and interesting aspects of the data that deserve discussion. The data show that Black-tailed Godwits occur in winter across a rather broad band of N Africa extending from Senegal, Guinea-Bissau, and Mali in the west, through northern Cameroon and Chad in Central Africa, to Egypt in the east. They are also found throughout the Mediterranean region, mostly in Portugal, Spain, Morocco, Tunisia, Greece and Turkey, with smaller numbers elsewhere. In addition they occur in the Middle East, with small numbers along the Arabian Peninsula and important numbers in Iran. However, it is not clear whether many of the birds found in the western Mediterranean spend the entire winter there or just move there at the beginning of their northward migration. There are significant numbers of Icelandic Black-tailed Godwits in Portugal and Spain throughout the winter. As these are very difficult to distinguish from Continental Black-tailed Godwits, it is not yet known whether the Continental subspecies also winters in southern Europe. It is unlikely that they winter in the area of the rice fields, which is their main stopover area in Iberia during northward migration (Lourenço & Piersma 2008, Sánchez-Guzmán et al. 2006), because godwits are absent from the rice fields until December, the main arrivals occur in January and they depart in March (Beintema et al. 1995, Kuiper et al. 2006). In autumn, Morocco and Turkey support significant numbers of godwits during southward migration but fewer in spring (de Roder 1985, Groen & Zomerdijk 1994). During northward migration, Continental Black-tailed Godwits start leaving their wintering areas as early as December (Kuiper et al. 2006). The largest numbers migrate through W Europe, especially Portugal, Spain and France. Ringing data show this is the main route for birds making for breeding grounds in the Netherlands (Beintema et al. 1995, Haverschmidt 1963), the country with the largest breeding population (Thorup 2006). Smaller numbers occur further east in the Mediterranean, in Italy, Greece and Turkey, which is
United Kingdom
5
Tunisia
3
Italy
3
Spain
2
Greece
2
Turkey
1
Denmark
1
Total
65
Scott 2006). However, these are not be treated here, as it is likely there is significant overlap with the Asian subspecies L. l. melanuroides in that region. The winter counts show that Continental Black-tailed Godwits have a wide range across N Africa and the Middle East, from Guinea-Bissau and Guinea in the west, through Mali and Egypt to Iran in the east (Tables 2 and 3). The northern limits of this distribution reach S Europe, as discussed below. To some extent temporal trends are obscured by lack of data, but it seems that the key wintering areas of Continental Black-tailed Godwits in Africa have changed in recent decades (Fig. 1). The large numbers formerly found in Senegal have dwindled to just a few thousand, and although Guinea-Bissau is still a key area, it seems to have lost some of its past importance. The Niger Inland Delta in Mali may have also shown a decrease in recent years, though this conclusion depends entirely on one very low count of 6,000 in 2007 (Trolliet et al. 2008). In contrast, peak counts in the Lake Chad basin remain similar to those of the 1980s. Further north, the wintering population of Morocco appears to have lost its past importance, while increasing numbers have occurred in Portugal and Spain early in the calendar year. In the east, Iran is the key wintering area, with some less important sites scattered around the Mediterranean. During spring migration, key stopover sites are in Portugal, Spain and France, although large numbers remain in Mali as late as Feb and Mar (Table 4). Other countries used by Black-tailed Godwits in spring include Tunisia, Italy, Greece and Turkey (Fig. 2). The data are so patchy that temporal trends are difficult to discern. However, numbers seem to have increased in Iberia, while in France there has been a
Table 2. Mid-winter (Nov–Jan) Continental Black-tailed Godwit count data for the 1950s, 1960s and 1970s, a period when information was only available for a limited number of countries and sites. Data are presented as means and, when possible, range, and sample size is indicated in parentheses whenever n > 1. 1950s Morocco: Merja Zerga
1960s
1970s
References
80,000–120,000
10,000
1, 2
Portugal: country total Senegal: Senegal delta
>100,000
10,000
Spain: country total Turkey: country total
620
10,867; 7,307–14,427 (n = 2)
3
13,000; 5,000–20,000 (n = 4)
4–7
6,147
8
595; 550–640 (n = 2)
9
References: (1) Blondel & Blondel 1964, (2) Zwarts 1972, (3) Rufino 1984, (4) Roux 1959, (5) Morel & Roux 1966, (6) Roux 1973, (7) Tréca 1975, (8) Alberto & de Velasco 1988, (9) KuşBank website (2007).
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Lourenço & Piersma: Changes in non-breeding distribution of Continental Black-tailed Godwits
Table 3. Mid-winter (Nov–Jan) count data for Continental Black-tailed Godwits for the 1980s to 2007. Data are presented as means and, where possible, range. Sample sizes are indicated in parentheses whenever n > 1. 1980s
1990s
2000s
References
Albania: Country total
239; 163–314 (n = 2)
1; 2
Algeria: Country total
423
2
Azerbeijan: Country total
896
1
Chad & Cameroon: Lake Chad basin
9,203; 324–30,365 (n = 6)
2,691
Egypt: Nile delta Country total Gambia: Camaloo Country total
36,528
935 1,335
4 4
800 5,500; 1,000–10,000 (n = 2)
112
Greece: Axios delta Country total
1,002
17,400
Guinea-Bissau: Country total
110,000–120,000
Italy: Country total
106; 103–112 (n = 3)
Iran: Country total
10,418; 4,878–17,170 (n = 3)
Israel: Country total
5 6; 7; 8 9 2
Guinea: Kamsar-Kibola Coastal mudflats
3; 40
211
8
1,480
10; 11
35,000–40,000
6; 8
10,000
1; 2; 12
1; 2
278; 167–346 (n = 5)
1; 2
Mali: Niger Inland Delta
42,164; 40,492–45,000 (n = 3)
40,333; 40,000–41,000 (n = 3)
28,756; 5,987–40,280 (n = 3)
8; 13; 14; 40
Morroco: Sidi Moussai Merja Zerga Country total
500; 100–1,000 (n = 8) 5,056; 1,200–10,000 (n = 9) 15,250; 15,000–15,500 (n = 2)
456; 100–1,000 (n = 9) 7,820; 2,400–16,800 (n = 10) 19,870
375 4,456 5,411
7; 15–17 8; 15–17 1; 6; 8; 15
Oman: Country total Portugal: Tejo rice fields Sado rice fields Country total
247 51,400 11,397; 10,246–12,547 (n = 2)
30,143; 2,293–56,935 (n = 10)
Saudi Arabia: Country total
2 13,437; 3,723–23,150 (n = 2) 7,701; 4,401–11,000 (n = 2) 10,509; 130–24,086 (n = 6)
446
Senegal: Senegal delta Casamance River Sine-Saloum delta
6,650; 3,300–10,000 (n = 2) 1,600 3,850; 2,700–5,000 (n = 2)
4,167; 1,000–11,000 (n = 7)
Spain: Extremadura rice fields Country total
13,820; 1,826–25,888 (n = 5)
22,067; 10,547–29,854 (n = 3)
Tunísia: Gul of Gábes
1,710
Turkey: Sultanazligi Kizilirmak delta Country total
1,065; 380–1,750 (n = 2) 1,277; 523–2,853 (n = 3)
18; 19 19 2; 20–29 1
2,390; 1,000–5,613 (n = 7) 329 390
6; 8; 30; 31; 40 6; 8 6; 8; 30
12,000 19,013
8 2; 32; 33 34
400 617
815; 445–1,000 (n = 3)
35; 36 37 1; 36–39
UAE: Country total
115
2
Yemen: Country total
160
2
References: (1) Delany et al. (1999) (5) Gore (1990) (9) Goutner et al. (2005) (13) Wymenga et al. (2002) (17) Groen & Zomerdijk (1994) (21) Rufino (1988) (25) Rufino (1993) (29) Costa & Rufino (1997) (33) Gútierrez (2005) (37) KuşBank website (2007)
(2) Gilissen et al. (2002) (6) Jensen (1980) (10) Altenburg & van der Kamp (1991) (14) van der Kamp et al. (2005) (18) Beintema et al. (1995) (22) Rufino (1989a) (26) Costa & Rufino (1994) (30) Poorter et al. (1982) (34) van Dijk et al. (1986) (38) Dijksen & Koning (1986)
probably the route used by the birds that breed to the northeast of the Netherlands. In W Africa, particularly in Senegal, Gambia, GuineaBissau and Morocco, the wintering population has declined in recent decades. This reflects the dramatic decline in the breeding population of W Europe (Nijland 2002, Teunissen 2005). Only in Mali and Chad have numbers remained stable
(3) van Wetten & Spierenburg (1998) (7) Altenburg & van der Kamp (1985) (11) Trolliet & Fouquet (2004) (15) Kersten & Smit (1984) (19) P.M. Lourenço (unpub. data) (23) Rufino (1989b) (27) Costa & Rufino (1996a) (31) Tréca (1984) (35) van den Berk (1983) (39) Dijksen & van der Wolf (1987)
(4) Meininger & Atta (1994) (8) Kuiper et al. (2006) (12) van der Have et al. (2001) (16) van den Berg (1988) (20) Rufino (1984) (24) Rufino (1992) (28) Costa & Rufino (1996b) (32) Alberto & de Velasco (1988) (36) de Roder (1985) (40) Trolliet et al. (2008)
over the last thirty years; perhaps because that population has a different breeding origin, which is probably E Europe (Beintema et al. 1995, Kuiper et al. 2006), where the population may have been less affected by the consequences of agricultural intensification. It appears that increasing numbers of Black-tailed Godwits have occurred in the Iberian Peninsula in recent years. This
94
Wader Study Group Bulletin 115 (2) 2008
might be explained by the increase in rice farming, especially in Spain, where the new rice fields have provided important feeding habitat (Lourenço & Piersma 2008, Sánchez-Guzmán et al. 2006). The rice fields, especially those in Portugal, also support important numbers of the increasing Icelandic Blacktailed Godwit population throughout the winter (Gunnarsson et al. 2005). Mostly, however, there is habitat segregation between the subspecies, so most birds counted in the rice fields are limosa and most using tidal and other natural wetlands are islandica (Beintema et al. 1995) though there is some mixing of the two populations (pers. obs.). Numbers in France have declined, which might be either the result of a change in migratory habits, with more birds stopping-over
3000
0
3000
in Iberia and over-flying France, or simply a consequence of the general decrease of the W Europe population. These data have enabled us to identify some key areas for the conservation of the Continental Black-tailed Godwit. In Africa, the most important wintering areas are shown to be Guinea-Bissau, the Niger Inland Delta in Mali and the Lake Chad basin in Chad and northern Cameroon. Senegal might also be important for Black-tailed Godwits, but the role of Morocco is somewhat unclear. Further north around the Mediterranean, key sites include the rice fields near the Tejo and Sado estuaries in central Portugal, as well as the Coto Doñana marshes and the Extremadura rice fields in Spain. The Gulf of Gabés in Tunisia and the Pó River rice plantations in
1980s
1980s
1990s
1990s
2000s
2000s
6000
Kilometres
Fig. 1. Changes in the mid-winter (Nov–Jan) distribution of Continental Black-tailed Godwits over the three decades, the 1980s, 1990s and 2000s. The symbols on the maps indicate the decade average for each site.
3000
0
3000
6000
Kilometres
Fig. 2. Changes in the spring migration (Feb–Mar) distribution of Continental Black-tailed Godwits over the three decades, the 1980s, 1990s and 2000s. The symbols on the maps indicate the decade average for each site.
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Lourenço & Piersma: Changes in non-breeding distribution of Continental Black-tailed Godwits
Table 4. Spring migration (Feb–Mar) count data for Continental Black-tailed Godwits for the 1970s to 2007. Data are presented as means and, where possible, range. Sample sizes are indicated in parentheses whenever n > 1. 1970s
1980s
1990s
2000s
Chad: Lake Chad
883
Egypt: Nile delta France: Vallées Angevines Moëze-Oléron Marais Poitevin
12,605; 4,200–16,900 (n = 10)
200
388
17,650; 8,850–37,700 (n = 10)
7,265; 800–20,000 (n = 10)
36,250; 25,000–50,000 (n = 4)
7,010; 2,300–15,400 (n = 5) 146
Corsica Greece: Messolonghi delta Amvrakikos Italy: Po delta and NE coast Sicily
1,560
Morocco: Sidi Moussai Merja Zerga
20,635
Spain: Extremadura rice fields Coto Doñana 600 2,029; 200–3,862 (n = 4)
Turkey: Kizilirmak delta Akyatan Gölü Country total
9
2,860
10
2,923
7,091
4; 11–13
27,000
22,907; 7,000–38,000 (n = 7)
4; 15
14
16 16 38,825; 33,200–51,385 (n = 5) 5,350; 3,250–7,450 (n = 2)
30,667; 23,000–44,000 (n = 3) 8,433; 2,700–19,700 (n = 3)
4; 17
21,000
4
ACKNOWLEDGEMENTS We would like to thank the help of Savas Kazantzidis and Christos Barboutis for help obtaining data for Greece, and Kiraz Erciyas for providing information for Turkey. Thanks also to J. Gill for her very constructive comments on a previous version of the manuscript.
4; 17
17,923; 7,190–31,281 (n = 6)
4
810; 446–1,288 (n = 3)
18; 19 4; 11; 18; 20–24
300
25
1,134
26 26
900
3,725
Italy also support significant numbers. In France, key areas that have retained their importance are the Marais Poitevin and the Vallées Angevines. Further east, wetlands of importance for the Continental Black-tailed Godwit include Amvrakikos and the Messolonghi delta in Greece, as well as Kizilirmak and Akyatan Gölü in Turkey. The Persian Gulf, coast of Iran also appears to be a particularly significant wintering area, probably for birds belonging to the most easterly part of the breeding population.
4 4–7 8
710
(2) Goodman et al. (1989) (6) Sériot (1993) (10) S. Kazantzidis (pers. comm.) (14) Iapichino & Massa (1989) (18) Hovette & Kowalski (1972) (22) Wymenga & Klazenga (1989) (26) KuşBank website (2007)
4–7
600
9,330
Tunisia: Gulf of Gabés Country total 288; 116–460 (n = 2)
References: (1) Ganzevles & Bredenbeerk (2005) (5) Wymenga & Altenburg (1989) (9) De Nobel (1995) (13) Serra et al. (1992) (17) P.M. Lourenço (unpub. data) (21) Gaultier (1989) (25) Hustings & van Dijk (1993)
12,350; 6,550–25,000 (n = 7) 6,000 1,500; 1,000–2,000 (n = 2)
360 659
Portugal: Tejo rice fields Sado rice fields
1 2; 3
400
Mali: Niger Inner Delta
References
(3) Meininger & Atta (1994) (7) Kuiper et al. (2006) (11) Beintema et al. (1987) (15) van der Kamp et al. (2005) (19) van Dijk et al. (1986) (23) Azafzaf (2002)
(4) Blanchon (1989) (8) Thibault & Bonacconi (1999) (12) Serra & Baccetti (1991) (16) Kersten et al. (1983) (20) Goldschmidt & Hafner (1973) (24) Azafzaf & Azafzaf-Feltrup (2004)
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Part of a flock of 25,000 Black-tailed Godwits flying over a rice field near Porto Alto, Portugal. (Photo by Gareth Harris.)
