JUKEMA J, WYMENGA E & PIERSMA T (2001) Stopping over in SW Friesland: fattening and moulting in Ruffs Philomachus pugnax during northward migration in The Netherlands. LIMOSA 74 (1): 17-26.

During their northward migration Ruffs stop over in the province of Friesland in the northern part of The Netherlands. The central and southwestern part of this province is one of the major spring staging sites of Ruffs in Western Europe. In spring 1998, a series of simultaneous counts was conducted at roosts in Friesland, whilst in the same spring 564 Ruffs were caught and ringed. In this paper the numerical presence of Ruffs is linked with the progress of weight increase and moult into breeding plumage
     From the analysis the following picture emerges: Early in spring arriving Ruffs are mainly males, which presumably belong to the Scandinavian and NW Russian breeding population. These males have wintered in majority in SW Europe. After a stop of a few weeks in Friesland, during which these birds start moulting into breeding plumage. they continue their northward migration. In the second half of March large numbers of male Ruffs arrive, after a non-stop flight, from African winter quarters. These males complete their moult into breeding plumage in Friesland and reach high departure weights. These weights and a few ringing recoveries indicate breeding grounds in central and eastern Russia.
     Females, which form a minority among migrating Ruffs in Friesland, arrive approximately three weeks later than the males. Most of them only slightly increase in weight during their stay. They are not expected to migrate long distances and are likely to originate from breeding populations in Scandinavia and NW Russia. Only few of the females reach high departure weights and are able to reach breeding areas more to the east.
     Census and ringing data show a strong predominance of males in Friesland, whilst at the same time in central and eastern Europe mainly females are present. This suggests a difference in migration route between sexes. It is discussed whether this is linked to differences in habitat choice and foraging strategy. Male Ruffs in Friesland mostly forage on welt-drained pastures where they presumably take earthworms and leatherjackets. Females in central and eastern Europe feed mostly on small food items like Chironomidae in wet habitats. Wet habitats nearly completely vanished in W-Europe due to drainage and agriculture-driven water management. Since wet habitats were still abundant in the first half of the 20th century, one wonders if this dramatic habitat change might have induced a change in migration strategy within Ruffs. Ruffs show us an intriguing picture of a species of which the sexes seem to behave like different species outside the courtship period. This undoubtedly has its roots in the pronounced sexual dimorphism and, as a consequence. the differences in 'energy-management' and foraging strategy.Ruff Philomachus pugnax

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