Wader population estimates in France resulting from the ... - CiteSeerX

France

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Wader population estimates in France resulting from the 1997/98 Non-Estuarine Coastal Waterbird Survey Bernard Deceuninck, Roger Mahéo & François Gabillard Deceuninck, B., Mahéo, R. & Gabillard, F. 2008. Wader population estimates in France resulting from the 1997/98 Non-Estuarine Coastal Waterbird Survey. pp. 23–30. In: N.H.K. Burton, M.M. Rehfisch, D.A. Stroud & C.J. Spray (eds). The European Non-Estuarine Coastal Waterbird Survey. International Wader Studies 18. International Wader Study Group, Thetford, UK. France-NEWS was run in parallel to the mid-January International Waterbird Census (IWC) in January 1998. It covered about 50% of France’s open (non-estuarine) coasts and recorded 106,512 waders on this habitat, which is some 17% of the 632,246 waders counted along the whole French coast. A total of 152,925 ­waders was estimated to be present on non-estuarine sites in France. Open coasts in France hold more than 5% of the European wintering populations estimates of Common Ringed Plover Charadrius hiaticula (6,200: 10%), Grey Plover Pluvialis squatarola (8,200: 6.8%), Sanderling Calidris alba (9,800: 20.8%) and Ruddy Turnstone ­Arenaria interpres (5,700: 7.1%). The two most common species on non-estuarine sites are Dunlin Calidris alpina (53,500: 4.1%) and Northern Lapwing Vanellus vanellus (38,000: 1.4%). In combination with data gathered as part of the IWC, France-NEWS made it possible to revise the French population estimates of all waders, with the exception of Eurasian Golden Plover Pluvialis apricaria, Northern Lapwing, Jack Snipe Lymnocryptes minimus, Common Snipe Gallinago gallinago and Eurasian Woodcock Scolopax rusticola that winter in large numbers in areas not covered by these counts.

Length of non-estuarine coast

a 75%

Coveragea

Representative of

Winter

Population estimate

Reliability

5,706 km

70%

France

1997/98

Expert extrapolation

Average

3,652 km

75%

Atlantic & Channel coasts

1997/98

Expert extrapolation

Good

2,054 km

0%

Mediterranean coast

1997/98

No estimate

–

represents the percentage of open coast sites used by waders on the Atlantic and Channel coasts covered by the survey;

70% represents the percentage of waders present on France’s open coasts estimated to have been counted.

Introduction

to provide improved estimates of the numbers of waders on such habitat, and by so doing help to revise the estimates of the numbers of waders wintering in France. In France, major nature and hunting reserves are designated in estuarine sites. By reporting on the extent to which some wader species are concentrated on non-estuarine coasts, this paper demonstrates that some wader species are not as well protected as they could be.

Situated in Western Europe, France has a climate mostly under temperate maritime influence, with mild winters. Wetlands have only been subjected to long periods of freezing five times between 1970 and 1999. These conditions are conducive to wintering waterbirds. Wildfowl (geese, ducks and coots) and wader counts started in France in the 1960s and in 1976, respectively, under the auspices of the International Waterbird Research Bureau (now Wetlands International). Since January 1993, the co-ordinated mid-January national counts cover all estuaries and major non-estuarine areas holding large numbers of waterbirds. These counts include all waterbird species and contribute to Wetlands International’s International Waterbird Census (IWC). Almost 1,000,000 geese, ducks and coot (Deceuninck et al. 2002) and over 1,000,000 waders are counted in mid-January on every wetland (Deceuninck 2003), and over 2,000,000 gulls winter in France (Créau & Dubois 1997). The 6,460 km long coastline of France (Durand 1995) is of particular importance for waterbirds due to the large areas of intertidal zone uncovered by tides of 4–6 m average amplitude. By aiming to increase the coverage obtained of France’s open coasts, the January 1998 Non-Estuarine Coastal Waterbird Survey in France (France-NEWS) aimed

Methods The coastline of France is divided into sandy, rocky and man-made coasts as well as bays and estuaries (Table 1). In this paper the Channel coast is defined as going from the Belgian border to Brest, the Atlantic coast goes from Brest to the Spanish border, and the Mediterranean coast includes the coast of Corsica (Figure 1). Sandy coasts include mainly beaches bordered by dunes, rocky shores include sea cliffs and rocky platforms exposed at low tide, man-made coasts include ports, marinas and coastal sea-defences, and bays and estuaries comprise the most sheltered habitat where active sedimentation contributes to some 1,300 km2 of intertidal habitat. For the purposes of this paper, the 5,706 km of sandy, rocky and man-made coasts are defined as non-estuarine. 23

Europe-NEWS

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Table 1. The length (km) and percentage (in brackets) of the coastal habitats that make up France’s coastline (Durand 1995). Coastal type Channel coast Atlantic coast Mediterranean Coast

Sandy (%) 787 (37) 986 (44) 637 (31)

Rocky (%) 780 (37) 653 (29) 1,070 (51)

Man-made (%) 259 (12) 187 (8) 347 (17)

Bays and estuaries (%) 291 (14) 438 (19) 25 (1)

Total 2,117 2,264 2,079

Total

2,410 (37)

2,503 (39)

793 (12)

754 (12)

6,460

Figure 1. Distribution of major coastal survey sites. The site names are given by départment (administrative area) going counter-clockwise from “Nord”. Below the names of the départements are underlined. Channel sites – Nord: 40 Littoral Dunkerquois; Pas-deCalais: 45 Littoral du Pas de Calais; Somme: 01 Littoral Picard 12 Basse Vallée d’Authie et marais arrières littoraux. NORMANDY: Seine-Maritime: 01 Sites côtiers de Seine-Maritime; Eure: 19 Estuaire Seine & Marais Vernier; Calvados: 01 Littoral de Courseulles à Arromanches 19 Littoral Augeron; Manche: 01 Baie des Veys 03 Côte Ouest Cotentin 08 Littoral de la Pointe de Saire à Aumeville-Lestre. BRITTANY: Ille-et-Vilaine: 01 Baie du Mont Saint Michel 02 Rance Maritime 28 Cote à l’ouest de la Pointe du Grouin; Côtes d’Armor: 01 Baie de La Fresnaye & St Jacut de la Mer 02 Yffiniac-Morieux 39 Rance 40 Estuaires de Trieux Jaudy et Anse de Paimpol 97 Baie de Lannion; Finistère: 01 Baie de Morlaix & Penzé 02 Baie de Goulven 03 Aber-Benoît 04 Rade de Brest. Atlantic Coast sites – BRITTANY: Finistère: 06 Baie d’Audierne 07 Rivière de Pont l’Abbé 09 Baie de Douarnenez 12 Baie de Kerogan 34 Baie de Guisseny 35 Littoral Plouescat-Roscoff; Morbihan: 31 Golfe du Morbihan 32 Baie de Vilaine 34 Baie de Quiberon 35 Rade de Lorient 36 Rivière de l’Etel 37 Presqu’île de Rhuys. CENTRE-WEST: Loire-Atlantique: 28 Presqu’île Guérandaise 30 Loire

Aval 31 Sud-Loire; Vendée: 02 Marais d’Olonne 17 Baie de l’Aiguillon et Pointe d’Arçay 26 Littoral Vendéen 27 Baie de Bourgneuf et Noirmoutier; Charente-Maritime: 02 Ile de Ré 04 Réserve Naturelle de Moëze (Charente-Seudre) 05 Côtes Nord et Ouest de l’Ile d’Oléron 06 Baie de Bonne Anse 23 Marais littoraux et côtiers de CharenteMaritime. SOUTH-WEST: Gironde: 04 Bassin d’Arcachon 05 Côte Médocaine 14 Marais du Nord Médoc 19 Marais du Blayais; Pyrénées-Atlantiques: 02 Littoral Basque de Hendaye à St-Jean-de-Luz. Mediterranean Coast sites – Pyrénées-Orientales: 01 Etang de Canet (ou de St Nazaire); Aude: 12 Etangs du Narbonnais 13 Etangs Leucatois; Hérault: 22 Etangs Montpellierains 23 Etangs de Thau et de Bagnas 24 Basse Plaine de l’Aude; Gard: 01 Salins d’Aigues-Mortes; Bouches-du-Rhône: 70 Complexe de l’Etang de Berre 99 La Camargue; Var: 10 Salins de Hyères et de Pesquiers; Haute-Corse: 01 Etang de Biguglia 03 Etang de Diana 04 Etang d’Urbinu.

France

Study design and objectives France-NEWS mainly collected data from non-estuarine IWC sites. Some sites that are not usually covered were surveyed in order to better evaluate the proportion of waders that winter in France outside of estuaries and protected areas. Count methods Due to the great diversity of wintering sites no general ­national monitoring protocol exists. Each site has to be surveyed using a specific method to deal with local constraints. Waders are counted on the rising tide, at high tide or at low tide with the final objective of a complete census of each functional unit. These functional units include primary and secondary roosts and feeding areas, and may also include rocky shores adjacent to a bay or estuary that are used as roosts. Individual Eurasian Oystercatchers Haematopus ostralegus, Common Ringed Plovers Charadrius hiaticula, Grey Plovers Pluvialis squatarola, Sanderlings Calidris alba, Purple Sandpipers C. maritima and Ruddy Turnstones Arenaria interpres, in particular, found on such rocky shores are thought to use the bays and estuarine habitat, while others feed on non-estuarine or open coast. Count quality is generally high because the large majority of the counters know the functional sites very well and have been counting waterbirds on their sites for over 10 years. Count period France-NEWS counts were made between 1 December 1997 and 28 February 1998 and over 95% of the waterbird counts took place in January 1998, the IWC month. Count analyses The French IWC database held by LPO (LPO – BirdLife France 2004) allows stratified analyses. Every site location is associated with a habitat type (estuary, lake, reservoir, beach, etc.). Count data from open coast sites have been extracted to allow comparison with national totals. National and major coastal site totals have been published by Mahéo (1998). Total counts per species on open coast sites have been divided by total raw counts on coastal sites (estuaries + open coasts) in order to give the proportions of waders present on the open coast. With the exception of Purple Sandpiper, the wader counts recorded by France-NEWS were converted to national estimates of wintering waders on open coasts by dividing by 0.7 to allow for geographical coverage (see below and Table 2). A species-specific count of Purple Sandpipers, co-ordinated by P. Léon and G.O. Breton (unpublished data) was carried out in Brittany between 1996/97 and 1997/98. This survey showed that major Purple Sandpiper roosts are located outside the IWC sites in Brittany and thus are usually not counted in January. As few Purple Sandpipers have been counted outside IWC sites elsewhere in France, the results of this species-specific survey have been used to provide an extrapolated estimate of the Purple Sandpiper population wintering in France. As waders wintering in France come from various biogeographic populations (Stroud et al. 2004, Wetlands International 2006), it is not easy to evaluate what proportion of each is present in the country. Instead we estimate the percentage of the numbers of wader that winter in Europe (BirdLife

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International 2004) found in France (Table 2). Revised national population estimates of wintering ­waders are calculated by summing the IWC counts from January 1998 and counts for sites only covered during 1997/98 France-NEWS. Population estimates were calculated for all waders with the exception of Eurasian Golden Plover Pluvialis apricaria, Northern Lapwing Vanellus vanellus, Jack Snipe Lymnocryptes minimus, Common Snipe Gallinago gallinago and Eurasian Woodcock Scolopax rusticola that winter in large numbers in areas not covered by these counts.

Results Geographical coverage Along the coast, birds are counted on 97 functional sites by the IWC. Counts of bays and estuaries are prioritised because the majority of waterbirds winter on these habitats. However, good annual coverage is obtained from 26 sites situated on the open coast, beaches and rocky shores; the small beaches between rocky outcrops that are especially common in the regions of Brittany, Cotentin and the Loire-Atlantique are particularly well represented by these sites, as are large beaches in the Vendée, part of Charente-Maritime and North Gironde. A further 31 sites rarely visited during previous winters were surveyed as part of France-NEWS. These included the islands of Yeu, Hoëdic and Groix as well as some small islands difficult of access, notably those of Glénan, Sein and Molène in Brittany. In total, it was estimated that France-NEWS covered about 75% of the open coast sites used by waders on the Atlantic and Channel coasts. Elsewhere, including the southern Gironde, Landes, Pyrénées-Atlantique and the Mediterranean coast, open coasts were less well covered. The Mediterranean coast is unattractive to waders due to the absence of tides, and the Mediterranean beaches were not counted during the 1997/98 winter. However, its adjacent salinas and lagoons that hold waders were counted as part of the IWC counts, as is usually the case in winter. Altogether, therefore, we estimated that approximately 70% of the waders present on France’s open coasts were counted. Wader counts Of the almost 930,000 waders counted in France in midJanuary 1998 (Table 2), 632,246 (68%) were recorded along the coast (Mahéo 1998, LPO – BirdLife France 2004). Of the species concerned, only Northern Lapwing and Eurasian Golden Plover are known to be more common inland ­(Deceuninck & Mahéo 2000). Although 55% of the Eurasian Golden Plovers counted recorded by the January 1998 IWC counts were found on the coast (Table 2), this apparent majority in coastal habitats is due to no counts having been made of this species in agricultural landscapes where they, and Northern Lapwing, are widespread. Thus, the national estimates of wintering Northern Lapwing and Eurasian Golden Plover in France are only guesses based on known densities in agricultural landscapes: 1–10 individuals/sq km for Northern Lapwing and 0.2–2 individuals/sq km for Eurasian Golden Plover (Corbin unpublished data). Spotted Redshank Tringa erythropus: (13% of birds), Green Sandpiper T. ochropus (52%) and Common Sandpiper Actitis hypoleucos (27%) are often found on inland wetlands, but fewer than 350 individuals of each species are thought to winter in France (Deceuninck & Mahéo 2000).

8,918 0 176 1,844 2 36 2,160 4,962 505 4,086 0 161 13,711 0 25 701 1,673 0 472 22 5 18 2,085 41,562

NEWS Channel coast 3,265 0 762 2,528 2 1,207 3,600 21,647 39 2,797 108 234 23,736 0 490 808 1,027 30 715 37 3 3 1,912 64,950

NEWS Atlantic coast 12,183 0 938 4,372 4 1,243 5,760 26,609 544 6,883 108 395 37,447 0 515 1,509 2,700 30 1,187 59 8 21 3,997 106,512

NEWS total 17,400 5 1,350 6,200 5 1,800 8,200 38,000 800 9,800 150 1,4006 53,500 0 750 2,150 3,850 45 1,700 80 10 30 5,700 152,925

Non-estuarine coast estimatea,b 65,580 30 15,625 12,459 242 23,049 26,461 385,222 30,941 10,985 815 1,4006 305,005 329 6,727 7,265 19,796 337 5,258 178 129 177 8,102

Total no. recorded by the IWC in France in January 1998

b Numbers

a

2.1 0 3.0 10.0 0.1 0.2 6.8 1.4 0.2 20.9 1.6 1.8 4.1 0 1.2 1.8 0.9 3.2 0.9 3.1 0.3 1.9 7.1

% of European winter population found on France’s non-estuarine coastc

Rounded estimates = total raw count on non-estuarine coast divided by estimated coverage (0.7). 50,000 to nearest 500. c Source: BirdLife International (2004). d (Total January IWC counts made in 1998) + (counts for sites only covered during 1997/98 France-NEWS), rounded off following the convention described in (2) above. e Source: P. Léon and G.O. Breton (unpublished data) – only 509 individuals recorded by IWC.

Eurasian Oystercatcher Haematopus ostralegus Black-winged Stilt Himantopus himantopus Pied Avocet Recurvirostra avosetta Common Ringed Plover Charadrius hiaticula Kentish Plover Charadrius alexandrinus Eurasian Golden Plover Pluvialis apricaria Grey Plover Pluvialis squatarola Northern Lapwing Vanellus vanellus Red Knot Calidris canutus Sanderling Calidris alba Little Stint Calidris minuta Purple Sandpiper Calidris maritima Dunlin Calidris alpina Ruff Philomachus pugnax Black-tailed Godwit Limosa limosa Bar-tailed Godwit Limosa lapponica Eurasian Curlew Numenius arquata Spotted Redshank Tringa erythropus Common Redshank Tringa totanus Common Greenshank Tringa nebularia Green Sandpiper Tringa ochropus Common Sandpiper Actitis hypoleucos Ruddy Turnstone Arenaria interpres Total

Species

66,000 30 16,000 13,000 250 – 27,000 – 31,000 11,000 850 1,400e 305,000 350 11,000 8,000 22,000 350 5,500 200 150 200 10,000

Revised national population estimatesd

Table 2. Waders wintering along the non-estuarine coasts of France in January 1998, the percentage of the respective European winter population found on this habitat in France and the revised population estimates for France.

France

Bays and estuaries hold 83% of the waders counted on the coast. Pied Avocet Recurvirostra avosetta, Red Knot Calidris canutus and Little Stint C. minuta, Black-tailed Godwit ­Limosa limosa and Spotted Redshank are uncommon on open coasts (Table 2), whereas Sanderling, Purple Sandpiper and Ruddy Turnstone are found predominantly on this habitat. a. Eurasian Oystercatcher Haematopus ostralegus (France: 65,580 in January 1998 and France-NEWS: 12,183) Eighty-one percent of Eurasian Oystercatchers were counted in large bays and estuaries, especially along the Channel (Bays of the Somme and St Michaels Mount). The remainder of the Eurasian Oystercatchers winter along open coasts (Table 2), often near bays along the largely sandy beaches of the Channel (3,800 individuals or 31% of the birds of the open coast). Brittany, especially along its northern coast, holds over 600 individuals on open coast, principally on small islands and rocky shores. b. Common Ringed Plover Charadrius hiaticula (France: 12,459 in January 1998 and France-NEWS: 4,372) Sixty-five percent of Common Ringed Plovers were counted in large bays and estuaries. Common Ringed Plovers along open coasts are associated with small sheltered beaches and this helps explain their presence in a large number of locations and the absence of large concentrations (Figure 2). Some 37% are found in Brittany, especially in the south, 32% along the West Central coast and 28% in Cotentin. c. Eurasian Golden Plover Pluvialis apricaria (France: 23,049 in January 1998 and France-NEWS: 1,243) and Northern Lapwing Vanellus vanellus (France: 385,222 in January 1998 and France-NEWS: 26,609) These two species are found mainly inland. They use the coastal zones as a diurnal refuge before going to feed in

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a­ djacent inland areas, predominantly at night. In January 1998, 29% Northern Lapwing and 55% of Eurasian Golden Plovers were seen on coastal sites. The 26,609 Northern Lapwings and 1,243 Eurasian Golden Plovers recorded in January 1998 along the open coast comprised 7% and 5% of the national total recorded that month, respectively. Most of the birds counted on the coast were concentrated in bays and estuaries, 75% and 90% ­respectively. d. Grey Plover Pluvialis squatarola (France: 26,461 in January 1998 and France-NEWS: 5,760) Seventy-eight percent of Grey Plovers were counted in the large bays and estuaries of the Atlantic and Channel coasts with major concentrations in Normandy (Veys and St Michael Mount Bays) and especially in the Vendée (Aiguillon Bay) and Charente-Maritime (Moëze Nature Reserve). The distribution of the 5,760 birds along the open coasts is uneven, with 47% recorded along the coasts of the Centre-West (Vendée and Charente-Maritime). e. Sanderling Calidris alba (France: 10,985 in January 1998 and France-NEWS: 6,883) As Sanderlings are found on sandy beaches where they feed principally on Amphipod crustaceans it is not surprising that some 63% of individuals were recorded along open coasts (Figure 3). Birds are fairly evenly distributed on open coasts with slight concentrations in the Centre-West, Normandy and southern Brittany that hold some 30%, 24% and 20% of the open coast totals, respectively. f. Purple Sandpiper Calidris maritima (France: 509 in January 1998 on IWC sites and France-NEWS: 395) A species-specific count of Purple Sandpipers, co-ordinated by P. Léon and G.O. Breton (unpublished data), was carried out in Brittany between 1996/97 and 1997/98. It revealed

Figure 2. Common Ringed Plover distribution on the non-estuarine coasts of France during the winter of 1997/98.

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Europe-NEWS

Figure 3. Sanderling distribution on the non-estuarine coasts of France during the winter of 1997/98.

that a minimum of 1,400 individuals winter along the coasts of France, with more than half in Brittany. Thus, the 1998 mid-January IWC count covered at most 36% (some 509 individuals) of France’s population, and of these 395 were on the open coast. Purple Sandpipers, found almost uniquely along natural or man-made rocky shores, are unevenly distributed along the Atlantic-Channel coast. Most birds are found in Brittany, the islands of Oléron and Ré and more recently in Vendée ­(Desmots 2001), with 92% of the total count on open-coasts. g. Dunlin Calidris alpina (France: 305,005 in January 1998 and France-NEWS: 37,447) Eighty-eight percent of Dunlins, the most common coastal wader in France, winter on estuaries. Particularly high numbers are recorded along the coasts of the Centre-West (33,670, 15,000 and 14,750 in the Bays of Moëze-Oléron, Yves and Aiguillon, respectively). Of the 37,447 birds recorded along the open coasts, 36% were recorded in Normandy and a further 20% in the CentreWest. The remainder was evenly distributed in Brittany and the western Channel. h. Bar-tailed Godwit Limosa lapponica (France: 7,265 in January 1998 and France-NEWS: 1,509) Seventy-nine percent of Bar-tailed Godwits are in bays and estuaries with the largest concentrations being found in northern Brittany in the Bays of Saint-Brieuc and Goulven. Of the 21% of Bar-tailed Godwits found on open coasts, 100 individuals were on the enormous sandy beaches of Normandy, and the rest were recorded in Brittany, Vendée and Charente-Maritime.

i. Eurasian Curlew Numenius arquata (France: 19,796 in January 1998 and France-NEWS: 2,700) The few (