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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Comparative study of cavity-nesting passerines in urban and rural habitats
Auteurs :	Roswitha Junker-Bornholdt, Auteur ; Karl-Heinz Schmidt, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (121(2-3) 2000)
Article en page(s) :	129-153
Résumé :	Since 1970, we have conducted a study of cavity-nesting passerines in deciduous woods 70 km outside Frankfurt (50degree19' N, 09degree28 E). From 1980 onwards, the study was extended to include small woods, parks and cemeteries inside the city of Frankfurt (50degree05 N, 08degree40 E). In addition, we investigated two woods in the outskirts of Frankfurt. Inside and outside the city some 4000 nest-boxes were placed in several study plots. During the breeding season all females and nestlings were ringed. From August to March birds were mist-netted once a week at bird feeders. From November to March all nest-boxes were checked at monthly intervals and all roosting birds were ringed, sexed and aged. Status of juvenile moult, residues of lead, cadmium, zinc, and chlorinated hydrocarbons in tail feathers, blood, kidneys, liver, bones, and eggs were analysed. Population densities of cavity-nesting species were reduced in town populations. Town populations of Great Tits Parus major are characterized by a high proportion of resident juveniles and a low proportion of immigrants. In country populations, comparatively few breeding birds were resident juveniles and most were immigrants. Long-distance migrations were observed only in rural areas, both among immigrants and birds reared in the study area. Urban populations consisted of residents and short-distance migrants. Urban populations were much more contaminated with heavy metals than rural populations. Postjuvenile moult was more advanced in urban populations of Great and Blue Tits. Body weight and wing length of juvenile Great Tits were reduced in town populations. Town populations of Great and Blue Tits did not fluctuate in parallel with populations in rural areas. The strong fluctuations in rural areas were caused predominantly by large numbers of immigrants. The number of immigrants in the town was comparatively low and fairly constant between years. Clutch size and breeding success were considerably lower in the center of the town; poor feeding conditions were regarded as the main cause of the lower rate of reproduction. In the outskirts, clutch size and breeding success were much better than in the central areas. Despite of low numbers of fledglings in first broods, town populations did not decrease since 1980. A high proportion of replacement and second clutches and a reduced adult mortality compensate for low breeding success. The density of breeding birds was highest in one of the study plots in the outskirts. Urban populations seem to be isolated from rural ones. Differences between town and country populations are suspected to be adaptations to different habitats.

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