14 Devos, Melre & Kuijken:Belgium Recent Population Estimates of Meadow-Breeding Waders in Belgium Koen Devos, Patrick Meire & Eckhart Kuijken Devos, K., Meire, P. & Kuijken, E. 1991. RecentPopulation Estimates of Meadow-Breeding Wadersin Belgium.Wader Study Group Bulletin 61, Supplement:14-22. This papergives the recentpopulation estimates of meadow-breedingwaders in Belgium.These estimatesare mainlybased on unpublisheddata of regionalcensuses. As mostwaders species, with the exceptionof the Lapwing,are not verynumerous and occur in well surveyedareas, we canassume that the population estimates are quiteaccurate. The most importantbreeding areas in Belgiumare indicatedin Figure 1. The currentstatus of meadow-breedingspecies in the differentregions of Belgiumis givenin Table 1 andFigure 2. In Table 2, the breedingnumbers are compared with previousestimates. The recentpopulation estimates, trends in numbersand numeric distribution are discussedspecies by species.The populationof Oystercatchersis steadilyincreasing, mainly by rangeexpansion. Black-tailedGodwits show recent increases. Whether or not this will be a continuingtrend is not yet clear.Lapwing and Curlew populations remain fairly stable.Snipe and Redshank numbers are decreasingconsiderably. Different speciesshow a markedhabitat shift. Where possiblethis is discussed. The discussiondeals mainly with the threats for breeding waders and their habitat and summarizesthe situationin Belgium. Koen Devos, Laboratoryof Animal Ecology,State UniversityGent, KL. Ledeganckstraat35, 9000 Gent, Belgium, Patrick Meire & Eckhart Kuijken, Institute of Nature Conservation, Kiewitdreef3, 3500 Hasselt,Belgium. Introduction Belgium have been publishedregularly since 1957 (Verheyen 1957, Voet 1970, Lippens& The number of breeding waders in Belgium Wille 1972, Voet et al. 1982). is rather small in comparison to the populations in some nearby North Sea As the last estimateswere publishedalmost countries (Piersma 1986). This can be ten years ago, the aim of this paper is to explained by the small size of the country update the information on the numbers of and the fact that several speciesreach the breedingwaders in Belgium and to discuss southernlimit of their breedingrange in the the observed trends. northern part of Belgium. Despite this, severalregions in Belgium are characterized by their typical breeding populations of Materials and methods waders. Population estimates In contrastto, for example, The Netherlands and Great Britain, Belgium hasless tradition Former population estimates (Verheyen of monitoring breeding birds. Most wader 1957, Voet 1970, Lippens & Wille 1972) populationsare however restrictedto small were mainly the result of assemblingrelevant areas that are often of great importanceto regional papers (e.g. Devocht et al. 1974, nature conservation.Hence they are mostly Meeus et al. 1979, Van Gompel 1978) and covered by regional census programmes. correspondencewith local ornithologists. This makes it possibleto producereliable More recently, an atlas of breedingbirds in population estimates for most species. Belgium was published, mainly with Populationestimates of breedingwaders in information of the period 1973-1978 WSG Bulletin61, $uppl.: 14-22 (April 1991) Devos, Melre & KuiJken:Belgium 15 (Devillers et al. 1988). In 1981 a special Description of the most impor- breeding censusof waders was organizedin tant breeding areas Flanders(Voet et al. 1982). This review is also mainly based on The most important breeding areas are unpublisheddata of regional censuseswhich indicated in Figure 1. The letters and were kindly supplied to us by the co- numbers used in this text refer to those in ordinators. The information was collected Figurel. during the breeding seasonsof 1989 and 1990. In Flanders(A), the most importantbreeding areasare the polder areasalong the coast(1) and the Schelde estuary near Assenede (2) Accuracy of the estimates and Antwerpen(3), the 'Kempen'or Campine region (4) of the provinceof Antwerp (4a, c) The accuracyof breedingcensuses improved and Limburg (4b, c) and the alluvial plainsof considerablyduring the last 50 years,mainly several rivers. because of new census methods and an increasingnumber of birdwatchers.Breeding The 'Coastal Polders' (1) is a typical numbers in the past have often been agricultural area. In the lower parts, large underestimated.Population trends are hence grassland-complexesoccur, characterizedby the combined effect of methodological a typical microrelief and in someplaces still artifactsand real populationchanges. Where seepageof brackishwater. possible,the distinctionbetween both factors is made in the speciesaccounts. Of the 'Schelde Polders', two parts can be distuingishedin Belgium. In the 'Schelde The accuracynot only varies between years Polders near Assenede' (2), large creeks but also within a year. When compiling the occur but the amount of grasslandis rather presentpopulation estimates it becameclear small. Near Antwerpen small remnantsof the that not all speciesand all breedingsites in 'Beneden Schelde Polders' (3) remain after Belgium have been censusedwith the same huge areas have been destroyed for the intensity and accuracy. However, as most expansionof the harboursince the 1960s.On wader species are not very numerous and the left bank of the fiver Schelde this fallow occur largely in well-surveyedareas, we can land has not been used for many years and assume that the estimatesgiven below are some parts have become ornithologically now close to the actualpopulation sizes. The important. The value of these areas is Lapwing Vanellus vanellus, the most however only temporary.On the fight bank abundantspecies, is howevernot countedin most of the area is industrialized. many of its breeding areas. The population size can therefore only be estimatedwith a In the 'Kempen' in the province of Antwerp large degreeof uncertainty. ('Antwerpse Kempen', 4a) and Limburg ('Limburgse Kempen', 4b) very important Netherlands North Figure 1. Map of Belgium showingthe different regions of major importance for wadersbreeding on meadows: A Flanders 1. Coastal Polders; ß 2. Schelde Polders near Assenede; Germany 3. Beneden Schelde Polders; 4. 'Kempen', 4a. AntwerpseKempen; 4b. LimburgseKempen; 4c. Zuiderkempen; 5. Other areasin Flanders; France• B Southernpart of Belgium. WSG Bulletin 61, Suppl.: 14-22 (April 1991) 16 Devos, Meire & Kuijken: Belgium breeding areas of meadow birds occur. The southern part of the 'Kempen', the 'Zuiderkempen'(4c), is of minor importance. The former very extensive 'Kempische' moorlandshave largely been cultivated and are now restrictedto some relatively small areas. As the moorlands disappeared,most wader speciesmoved to the grasslandareas which now occur all over the area.Gradually, however, these are now being changed to arable land. Outside these areasmost breedingwaders are found in the alluvial plains of the river Schelde and its tributaries (5) and in the valley of the river Maas. In the southernpart of Belgium (B), with the * 0-5 exceptionof the Lapwing, very few breeding ß 6 - 2.5 waders occur. Most breeding is restrictedto • 26 - 100 the 'Condroz','Fagne' and 'Famenne'as well ß 101 - 200 as in the valley of the Haine. 201- 400 I > 400 Species accounts Figure 2. Numeric distribution of Oystercatcher Haernatopusostralegus, Snipe Gallinago gallinago, Black-tailed Godwit Limosa limosa, Curlew Nu- The breedingnumbers for the different parts menius arquata and Redshank Tringa totanusin of Belgium are given in Table 1 andFigure 2. Belgium, 1990. A summaryof the populationestimates since the middle of the 1950s is shown in Table 2. Oystercatcher Haematopus ostralegus As already mentioned,some of thesefigures have to be interpreted with care. Therefore The currentpopulation size can be estimated the results will be discussedspecies by at 610-640 pairs.It is a ratherwidespread and species. non-colonialspecies and thereforesometimes Table 1. Numbers of meadow-breedingwaders in different regions in Belgium in 1990. regions(see. Fig. 1) 1 2 3 4a 4b,c 5 B Oystercatcher 175-195 30 150 >130 48-53 >80 0 Lapwing + + 800 >3,000 + + 5,000-6,500 Snipe 0 0 0 0 30-35 0-3 15-25 Curlew 0 0 4 250-265 185-205 0 0 Black-tailed Godwit 272-285 2 100-105 400420 78-87 12-15 0 Redshank 59 04 85-90 2-5 0-2 0 0 WSG Bulletin61, Suppl.: 14-22 (April 1991) Devos, Melre & Kuljken:Belgium 17 Table 2. Numbers of breedingpairs of meadow-breedingwader speciesin Belgium: summary of the available data. years 1956 1968 1972 1977 1981 1990 Oystercatcher 16-20 65 60 170-175 380 610-640 Lapwing 1,300-1,500 >4,000 5,000 + > 15,000 + Snipe >60 45 80 + 115-130 45-65 Curlew 230-270 300-310 350 380-385 475 440-475 Black-tailed Godwit 150 225-235 240 >400 750-780 865-910 Redshank 160 180-190 190 190 210 145-160 Sources:1956- Verheyen1957; 1968- Voet 1970; 1972- Lippens& Wille 1972; 1981- Voetetal. 1982; 1990 - thispaper. +: not surveyed. difficult to countprecisely. However, as this the population in Limburg has doubled. In speciesis not very numerousand it is very the 'Beneden Schelde Polders', numbers conspiciouswe can assumethis estimate to increasedfrom 89 pairs in 1981 to 150 in be quite accurate. 1990. The speciesis also still expandingits breedingrange to the south,with a preference The increaseof the populationas illustrated for cultivatedland in river valleys. in Table 2 is largely a real one. Originally the Oystercatcherwas a rare breeding bird in In the most important breeding areas, the Belgium (< 20 pairs), restricted to some species