NIJLAND F, TIMMERMAN A & HOSPER U (1996) Breeding populations of meadow birds on cultivated land in the Dutch province of Friesland and the significance of grassland reserves. LIMOSA 69 (2): 57-66.

Traditionally, the province of Friesland, in the northern part of The Netherlands, has been rich in meadow birds. The province has an extensive area of open, cultivated land, predominantly grassland, which in 1991 measured approximately 185200 hectares. The main source for the calculation of the Frisian meadow bird populations are data collected by the Association of Frisian Bird Protection Societies (BFVW). The Oystercatcher, Lapwing, Black-tailed Godwit, Redshank, Common Snipe and Ruff populations in Friesland have been calculated on the basis of the BFVW data of 1991, covering 76 200 hectares of cultivated land. The data provided by the nature management organizations were used to calculate the numbers in grassland reserves. Two scenarios were used to process this material: 'Scrooge' and 'Big Spender'. In the former scenario the information was adjusted for the effects of insufficient representativeness, while in the latter the effect of counts falling short of the actual number of birds were taken into account. This has resulted in minimum and maximum population estimates, from which a mean value was derived. On the basis of these calculations, breeding populations in cultivated areas in Friesland in 1991 were estimated as follows: Oystercatcher 41 000, Lapwing 46 000, Black-tailed Godwit 30 000, Redshank 12 000, Common Snipe 1050, Ruff 200 (Tab. 1). The following estimates were made of the above species breeding outside cultivated areas: approx. 7000 Oystercatchers (tidal marshes, dunes, sand flats) and approx. 900 Redshanks (tidal marshes). Comparison with estimates show a distinct increase for the Oystercatcher population, a fairly stable situation for Lapwing and Redshank, a strong decline in the late seventies followed by stabilization in the eighties of the Black-tailed Godwit population, while Common Snipe and Ruff populations show a continued decline (Tab. 2). Species which are less successful in holding their own populations also show a less balanced distribution over the regions (soil types; Fig. 2). The management of reserves in Friesland has proved very successful. Compared with agricultural land the densities of the various populations in grassland reserves give the following scores: Oystercatcher and Lapwing twice as high, Black-tailed Godwit and Redshank well over three times as high, Common Snipe 13 times as high, while the Ruff practically exclusively breeds in reserves. This effect is even stronger in moist clay areas (Fig. 3). This can be attributed to the fact that reserves in this region are situated favourably and, in most cases, have their own water management. It is estimated that approx. 7% of the Lapwings and Oystercatchers, 11% of the Black-tailed Godwits and Redshanks, 34% of the Common Snipes and 85% of the Ruffs breed in the reserves, on three percent of the Frisian cultivated land. It is estimated that well over a third of the total Dutch populations of Oystercatcher, Black-tailed Godwit, Redshank, Common Snipe and Ruff and a fifth of the Dutch Lapwing population breeds in Friesland. Eurasian Oystercatcher Haematopus ostralegus Northern Lapwing Vanellus vanellus Black-tailed Godwit Limosa limosa Common Redshank Tringa totanus Common Snipe Gallinago gallinago Ruff Philomachus pugnax

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