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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Bar-tailed godwits (Limosa lapponica) in the Sylt-Romo Wadden Sea: Which birds, when, from where, and where to?
Auteurs :	Gregor Scheiffarth, Auteur
Type de document :	Article
Dans :	Vogelwarte (41(1) Oktober, 2001)
Article en page(s) :	53-69
Langues:	Allemand
Résumé :	In the Sylt-Romo Wadden Sea, a tidal catchment area in the northern Wadden Sea, Bar-tailed Godwits of two different populations stop over on migration between wintering and breeding areas. The Afro-Siberian population, which winters in West Africa and breeds in Siberia, uses roosts on the mainland coast only for one month each in spring and summer, whereas the European population, with wintering areas in Western Europe and breeding grounds in Fennoscandia, occurs mainly for three months in spring on the islands. Some birds also stay from autumn until late January. The European population was studied in detail in the Koenigshafen area at the northern end of the island of Sylt. Morphometric as well as ringing data confirmed that birds belonged to the European population with 13 out of 15 ringing recoveries in or from Great Britain. During the spring stopover, birds moulted from winter to breeding plumage in 43 days. On autumn migration, Bar-tailed Godwits arrived already with 1/4 winter plumage. Moult back into complete winter plumage took 28 days. Sex ratio was 1:1 throughout the year apart from i) the second half of May, when males left before females and ii) winter, when more males than females left the study area to overwinter in milder regions like the Dutch Wadden Sea or Great Britain. However, birds identified by colour rings in winter did not differ in size from all other birds colour ringed and not wintering in the Koenigshafen area. In spring, most colour marked birds arrived before the 24th of March and left after 30 - 40 days on the 3rd or 4th of May. A higher turnover of birds was observed in May as compared to March and April when Bar-tailed Godwits from other areas seem to concentrate in the northern Wadden Sea before final departure to the Fennoscandian breeding grounds. In autumn most marked birds arrived before 14th August. However, some birds arrived in early September, when a high turnover of birds occurred, since a proportion of the early arriving birds left for other wintering areas. On spring migration Bar-tailed Godwits seemed to be highly site-faithful whereas in autumn less than 25% of the birds ringed in spring were resighted. Assuming 100% site faithfulness in spring, maximum mortality rates ranged between 17.4 and 26% for adults which is far below previously published figures.

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