NIJLAND F & TIMMERMAN A (1990) Counts of migrant Common Snipes Gallinago gallinago on wet grasslands in the province of Friesland, The Netherlands. LIMOSA 63 (3): 94-101.

Counts of migrant Common Snipes Gallinago gallinago present in 16 grassland sampling areas (total 189 ha, fig. 2) carefully selected within a study area of621 ha (Groote Wielen, fig. I) were conducted during March-April and August-November of 1982,1984 and 1986. The study area comprised grassland (summer- and winterpolders), moorland and open water, and is situated east of the town of Leeuwarden, province of Friesland, in the northern part of The Netherlands. Apart from the direct results of the counts, we mainly evaluated three extrapolation models designed to obtain a realistic estimate of the total number of Snipes present in the study area. Mean maximum numbers of Snipes present in the study area amounted to 250 in spring and 1070 in autumn (fig. 3). The total number of birds present in autumn was always considerably larger than in spring, and numbers present in each of the two seasons differed very little between years. In spring, Snipe density in summerpolders was significantly higher than in winterpolders (means 0.86 and 0.22 birds/ha respectively, fig. 2). Summerpolders, being wetter, offer much more attractive habitat for Snipes in spring than do winterpolders in that season. Extrapolating separately per grassland type (viz., summer- and winterpolders) appears to be a more reliable method of estimating the size of the Snipe population in the study area than is straightforward singular extrapolation. Systematic errors of extrapolation due to factors such as the amount of (relatively attractive) ditch-banks (fig. 4) depend on differences in size and form among plots of grassland in the sample and study areas. In the present study these errors are estimated to be as small as c. 2%. Although the distribution patterns of Snipes on the sampling areas do not follow a clumped distribution, differences in Snipe densities between sampling areas are considerably high: sd c. 100%, probably due to social behaviour and the variability of field conditions in the study plots. This results in uncertainties in the number of birds calculated for the study area amounting to 34% (spring) and 24% (autumn). It is suggested that our methodology can be applied, and will be valuable, in attempts to estimate the number of migrant Common Snipes present in larger areas, viz. on regional and even national scales.

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