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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Phenology of herring, yellow-legged and Caspian gulls Larus argentatus, L-michahellis, L-cachinnans in Berlin in the years 2000-2004
Auteurs :	Klemens Steiof, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (127(2) 2006)
Article en page(s) :	99-117
Résumé :	Within five years, 187 counts of gulls were carried out at two night roosts in Berlin. In total, more than 73,000 large gulls were counted, of which about 29,700 individuals (41%) could be aged and identified at species level. The largest numbers occurred at Mfiggelsee, a lake of 7.7 km(2) on the edge of Berlin, which has traditionally been the largest night roost of gulls in the region of Berlin-Brandenburg (maximum count: 4,100 large gulls). The roost at Osthafen in the city centre was much smaller, with mostly some dozens or hundreds of large gulls, but more than 1,000 birds, when most of the suburban and rural lakes were ice-covered. Because Great Black-backed L marinus and Lesser Black-backed Gulls L. fuscus occurred only in very small numbers, usually 99% of the large gulls comprised of the three grey-backed species. There were almost no large gulls in Berlin in May and June; large breeding colonies are some 100-150 km away. After the breeding season the influx began in July with usually more than 150 birds. Numbers increased to more than 1,000 birds in October and peaked from December through February with an average of 3,200 large gulls in January. During March the majority of the gulls left Berlin. Yellow-legged Gull was dominating the roosts in July and August, as it is the earliest breeder of the three species in Europe. After its maximum in October (180 birds), the numbers dropped sharply in November and December, resulting in less than 20 birds in January, when most birds might have returned to the breeding colonies in the Mediterranean. A small peak of 60 birds in February may have included breeders of both central Europe and the Mediterranean. Herring Gull was the dominant gull species from late August or September onwards, with about 3,000 birds in January and February (maximum count 3,850). Whereas until December mainly adults occurred, a substantial influx of first-year birds was observed in midwinter, probably related to increasing numbers in the southern Baltic Sea, where many birds of northern origin arrive at this time. Herring Gulls of the yellow-legged type ('omissus') were seen in any month with a share of usually 1-5% of all Herring Gulls, although at some counts 8-14% of the adults had yellowish legs. The influx of Caspian Gulls started at the end of July and peaked in January with up to 160 birds. At least from July through September, Caspian and Yellow-legged Gull had slightly higher proportions at the roost Muggelsee, while Herring Gull had a higher proportion at the urban Osthafen. This might indicate different habitat needs, which perhaps have levelled off later in the season. In winter 2005/06, numbers of large gulls declined down to less than 10%, following reduced deposit rates of organic waste on refuse tips. This is a result of a new EU regulation.

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