Density dependent habitat selection of corridors in a fragmented landscape

This paper assesses the occurrence of density-dependent habitat selection i n an urban fragmented landscape, composed of forest fragments (urban parks) connected by corridors (wooded streets], to test the hypothesis that as po pulation density increased in the parks their suitability decreased and ind ividuals entered alternative habitats, such as wooded streets. Density vari ation of six species was studied during two consecutive breeding seasons. V egetation structure in wooded streets was significantly less complex than i n urban parks, supporting the view that wooded streets were less suitable f or breeding birds. Five species (Coal Tit Parus ater, Spotless Starling Stu rnus unicolor, Serin Serinus serinus, Black-billed Magpie Pica pica and Woo dpigeon Columba palumbus) showed density-dependent habitat occupation of wo oded streets, while the Common Blackbird Turdus merula did not. As park sui tability decreased with rising densities, wooded streets became a profitabl e alternative in terms of foraging, breeding, or for moving between parks. However, the relationships varied both between and within species in differ ent years. Such differences could have been caused by variable rates of hum an disturbance, renewal of resources and predation risks in wooded streets. More detailed studies are required to determine how birds perceive and reg ulate their population dynamics in fragments and associated corridors, part icularly for species targeted for management.