HOOIJMEIJER J, G VAN DER BURG & J POUTSMA (2010) Waders and waterfowl along the Frisian coast of lake Ijsselmeer in 1975-2000. LIMOSA 83 (2): 75-83.

Sandbanks, wet grasslands and shallow coastal waters along the Frisian coast of Lake IJsselmeer (Fig. 1) provide thousands of waders and waterfowl with an ideal place to rest, feed and moult. Counts in the seventies and eighties revealed that for more than 20 species more than 1% of the flyway population was regularly found in the area. Therefore, in 1991 approximately 5000 ha of the coastline got a sanctuary status. In this paper we compare maximum bird numbers for 62 species for two different time periods (1975-1984 and 1995-2000). Information about bird numbers was available from aerial surveys, counts from the shore during daytime, roosts counts, and casual observations (Table 1). Our results show that numbers of some species have changed dramatically over the last 25 years (Tables 2 and 3, Fig. 2). However, major differences in survey methodology make it hard to draw firm conclusions. On the other hand, for most species the trend is prominent, and coincides with information from other studies. Generally, herbivores (geese, swans, Wigeon Anas penelope) are doing well, while piscivores and waders have declined. Agricultural intensification and intensive fisheries could play an important role in explaining these patterns. Despite the decline of many species, the area is currently still of major importance for many bird species, notably Great Cormorant Phalacrocorax carbo, Barnacle Goose Branta leucopsis, Greater Scaup Aythya marila, Caspian Tern Sterna caspia and Ruff Philomachus pugnax (Table 3). It is therefore highly recommended to continue the long series of aerial surveys started in the 1970s and the standardized daytime and roost counts started in the mid 1990s.

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