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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	[Roof-top breeding gulls in Arhus city and Denmark]
Auteurs :	Ole Lilleor, Auteur
Type de document :	Article
Dans :	Dansk Ornitologisk Forenings Tidsskrift (94(4) 2000)
Article en page(s) :	149-156
Langues:	Anglais
Résumé :	The population of gulls breeding on roofs in Arhus, Denmark, was mapped during the breeding season of 1999. The roofs were scanned from several vantage points in the city or, in some cases, from the ground. A total of 173 pairs of Herring Gull (probably representing more than 90% of the actual population), 12 pairs of Lesser Black-backed Gull and 1 pair of Common Gull (on a wharf) were found. All Lesser Black-backed Gulls nested within or close to colonies or groups of Herring Gulls. The majority of the Herring Gulls (62%) bred in harbour, railway or industrial areas, most as members of one of the four small colonies located here. 31% nested in the densely build-up city centre, while the rest were found on modern apartment buildings. The colonies were placed on flat or slightly sloping roofs. Flat roofs were also the most common nest site among solitary breeding pairs, but some of them bred on steeper roofs. In most cases the nest was placed close to a roof structure that supported the nest or, perhaps, provided some kind of protection. Nests were placed on north-facing roofs more often than on south-facing roofs which, perhaps, may get too hot in the sun. The first roof-top breeding Herring Gulls in Denmark were found in Arhus in 1982; seven pairs were breeding in the city centre in 1985 and an estimated 32 pairs in 1992. The Lesser Black-backed Gulls found during the study, are the first roof-top nesters of this species reported from Denmark. In order to obtain a general impression of the occurrence of roof-top breeding gulls in Denmark, 24 wildlife advisors were interviewed by the author. The wildlife advisors have the authority to effectuate control measures and are therefore contacted by people complaining about gulls. Many birdwatchers were likewise asked about city-breeding gulls. It was not possible to get reliable information from all parts of the country, but the interviews revealed that Herring Gulls and Common Gulls breed in several coastal towns, totalling at least 1000 pairs and 650 pairs, respectively. Numbers are probably highly underestimated, however. The total Danish population of the two species is 55-58000 pairs of Herring Gulls and 25-30000 pairs of Common Gulls.

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