Birds and Butterflies in Swedish Urban and Peri-urban Habitats: a Landscape Perspective

Hedblom, M. 2007. Birds and butterflies in Swedish urban and peri-urban habitats: a landscape perspective. Doctor's dissertation. Urbanisation is considered to be one of the largest threats to biodiversity although little is known about the effect of habitat fragmentation on native flora and fauna in urban areas in general, and in Sweden specifically. In this thesis, data have been collected using remote sensing analyses of 100 cities, bird surveys in 34 cities, and experiments have been used to answer specific questions regarding dispersal and reproduction in different urban habitats. The dual processes of infill development and expansion of cities threaten remaining unprotected urban woodlands. Results showed that between 1 and 40% (average of 20%) of the proportion of the city area were comprised of urban woodland. Urban and peri-urban (surrounding) woodlands covered an area larger than the total area of protected forests in Sweden and had higher amounts of dead wood than typical non-protected forests. In contrast to previous studies, this thesis showed that many bird species breeding in urban woodlands were strongly affected by the surrounding city or landscape composition. On a smaller spatial scale (200 m), adjacent habitats affected population density and nestling quality of great tits Parus major breeding within urban woodlands. Movement corridors were only used by butterfly habitat specialists, and grassland corridors of intermediate quality seemed to be most efficient to promote dispersal among habitat fragments. In this thesis, I show that Sweden have relatively high proportion urban woodlands; urbanisation does not necessarily lead to a homogenisation of the bird fauna; urban habitats need to be well described in detail to allow comparisons among studies; bird faunas of local urban woodlands differ among regions and are strongly affected by composition of habitats both at city and landscape levels; movement corridors may be an efficient conservation tool if specifically managed to fit the autecologies of the species of conservation concern. krävs att korridorernas skötsel är direkt anpassad till de arter som ska gynnas.