CASTELIJNS H, MARTEIJN ECL, KREBS B & BURGGRAEVE G (1988) Wintering Ruffs Philomachus pugnax in Sw. Netherlands and NW. Belgium. LIMOSA 61 (3): 119-124.

Ruff Philomachus pugnax Since 1943, Ruffs have been found wintering in SW. Netherlands (fig I). In the period 1943-58 numbers were very small (1-5); between 1958-80 tens of birds wintered in the Braakman with a maximum of 130 birds in 1980. Also in other parts of the region only several tens of Ruffs were observed till 1974, although occasionally much larger flocks were noted. Since 1973/74 (NW. Belgium) and 1976/77 (SW. Netherlands), a considerable increase in numbers of wintering Ruff has been noticed (fig. 2). In the winters 1982/83-1985/86, on average 2000 Ruffs occurred in SW. Netherlands (Braakman) and NW. Belgium (Zwin). Only during periods of severe frost birds left the area as long as the period of adverse weather lasted (fig. 3). Two relatively nearby wintering areas are known (Bretagne, Sw. England). Assuming birds in Sw. Netherlands have the same weight as the ones wintering in the north of the country there will be no problem to reach these areas when low temperatures and snow force the birds to leave. Ruffs wintering in the Netherlands appear to be predominantly males (98%, n = 4098). Based on leg colour 93% of the males (n=41O) and 43% of females (n = 23) were adults. During daytime birds feed on meadows and arable land, especially when fluid dung has been sprayed on these parcels. During dusk, the birds fly to their night roosts (fig. I). The (main) roosts were located in water edges of two brackish inland creeks. The estimate of 2300 wintering Ruffs in Western Europe (Cramp & Simmons 1983) is considered to be too low. Combined winter data from France, United Kingdom, SW. Netherlands and NW. Belgium suggest a number of at least 4000. The relatively mild winter climate of the last two areas is probably the most plausible explanation for the choice of this wintering site. Weather circumstances closely resemble those in SW. England. Two questions are raised: (I) Why did the number of wintering Ruffs recently increase in Western Europe without obvious indications of an increasing population or amelioration of the winter climate? (2) Since the majority of Ruffs wintering in Africa are females, the question might be raised whether the sex ratio is far from an I: I ratio. Or are there still some unknown wintering sites, full of male Ruffs?

[free pdf] [dutch summary]