MEININGER PL, SCHEKKERMAN H & ROOMEN MWJ VAN (1995) Population estimates and 1%-levels for waterbird species occurring in The Netherlands: suggestions for standardisation. LIMOSA 68 (2): 41-48.

Population estimates and derived 1%levels have become widely used in the study and conservation of waterbird populations, both as an official criterion for assigning to wetlands the status of internationally important area under the Ramsar Convention, and in a more general sense, as a standard for interpretation and comparison of the importance of wetlands for waterbirds. This paper aims to present a comprehensive list of the most recent published population estimates for all waterbird species regularly occurring in The Netherlands. Population sizes and 1% levels are those presented by Rose & Scott (1994). For several populations for which no 1% level was mentioned by Rose & Scott, we have suggested one. It is proposed that our population estimates and 1% levels be used until revisions are published by IWRB. IWRB intends to publish a revision of population estimates of Western Palearctic waterbirds every three years, and a revision of 1% thresholds every nine years. For some species, separate population estimates and 1% levels are given for geographically distinct populations or subspecies. Application of these criteria is straightforward when populations can be distinguished in the field on the basis of plumage or geographical 10cation, but is problematic for waders, in which populations are often not distinguishable in the field, and overlap geographically during parts of the year. Fig. 2 summarises the occurrence of various populations of some wader species in The Netherlands by month, and indicates which population is most abundant in a given month. It is proposed that for each month, the 1%-level for the most abundant population be used; when it is unclear which population dominates, the highest level should be applied.Red-throated Diver Gavia stellata Black-throated Diver Gavia arctica Little Grebe Tachybaptus ruficollis Great Crested Grebe Podiceps cristatus Red-necked Grebe Podiceps grisegena Horned Grebe Podiceps auritus Black-necked Grebe Podiceps nigricollis Great Cormorant Phalacrocorax carbo Grey Heron Ardea cinerea Purple Heron Ardea purpurea Eurasian Bittern Botaurus stellaris Eurasian Spoonbill Platalea leucorodia Mute Swan Cygnus olor Bewick's Swan Cygnus bewickii Whooper Swan Cygnus cygnus Taiga Bean Goose Anser fabalis Taiga Bean Goose Anser fabalis Tundra Bean Goose Anser serrirostris Pink-footed Goose Anser brachyrhynchus = Anser fabalis brachyrhynchus Greater White-fronted Goose Anser albifrons Greylag Goose Anser anser Barnacle Goose Branta leucopsis Dark-bellied Brent Goose Branta bernicla Barnacle Goose Branta leucopsis Pale-bellied Brent Goose Branta hrota = Branta bernicla hrota Common Shelduck Tadorna tadorna Eurasian Wigeon Anas penelope Gadwall Anas strepera Common Teal Anas crecca Mallard Anas platyrhynchos Northern Pintail Anas acuta Garganey Anas querquedula Northern Shoveler Anas clypeata = Spatula clypeata Red-crested Pochard Netta rufina Common Pochard Aythya ferina Tufted Duck Aythya fuligula Greater Scaup Aythya marila Common Eider Somateria mollissima Long-tailed Duck Clangula hyemalis Black Scoter Melanitta nigra Velvet Scoter Melanitta fusca Eurasian Oystercatcher Haematopus ostralegus Pied Avocet Recurvirostra avosetta Little Ringed Plover Charadrius dubius Common Ringed Plover Charadrius hiaticula Kentish Plover Charadrius alexandrinus European Golden Plover Pluvialis apricaria Grey Plover Pluvialis squatarola Northern Lapwing Vanellus vanellus Red Knot Calidris canutus Sanderling Calidris alba Little Stint Calidris minuta Temminck's Stint Calidris temminckii Curlew Sandpiper Calidris ferruginea Purple Sandpiper Calidris maritima Dunlin Calidris alpina = Calidris alpina schinzii Ruff Philomachus pugnax Common Snipe Gallinago gallinago Black-tailed Godwit Limosa limosa Icelandic Black-tailed Godwit Limosa limosa islandica Bar-tailed Godwit Limosa lapponica Whimbrel Numenius phaeopus Eurasian Curlew Numenius arquata Spotted Redshank Tringa erythropus Common Redshank Tringa totanus Common Greenshank Tringa nebularia Wood Sandpiper Tringa glareola Green Sandpiper Tringa ochropus Common Sandpiper Actitis hypoleucos = Tringa hypoleucos Ruddy Turnstone Arenaria interpres Little Gull Hydrocoloeus minutus = Larus minutus Black-headed Gull Chroicocephalus ridibundus = Larus ridibundus Common Gull Larus canus canus Lesser Black-backed Gull Larus fuscus European Herring Gull Larus argentatus Great Black-backed Gull Larus marinus Black-legged Kittiwake Rissa tridactyla Sandwich Tern Thalasseus sandvicensis = Sterna sandvicensis Common Tern Sterna hirundo Arctic Tern Sterna paradisaea = Sterna macrura Nearctic Red Knot Calidris canutus islandicus

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