Species richness of breeding birds at a landscape scale:: which habitat type is the most important?

The aim of the study was to compare different habitat types according to species richness and estimate their value for total species richness at a landscape level. The study was carried out in the years 1995-2001 in the Tarnow region (1400 km(2), S Poland). All bird species were classified according to broadly defined breeding habitat type. Four main, easily distinguishable habitat types were specified: forests (18% of the area), open areas (70%), wetlands (1%) and anthropogenic areas (11%). Birds were classified as habitat specialists if they bred in only one habitat type, or as habitat generalists, if they bred in two or more habitat types. Altogether, 151 species nested in the study area, and a total of 87 species were habitat specialists. There were statistically more endangered species (so called "losers") among the habitat specialists than in the habitat generalists' group. Habitat specialists were also statistically less abundant than habitat generalists. The following numbers of species were recorded in the specific habitats: forests - 70, open areas 75, wetlands - 61, anthropogenic areas - 46. Among these, the percentages of habitat specialists were the following: forests - 41.4%, open areas - 18.7%, wetlands - 52.5%, anthropogenic areas - 26.1%. It was found that the numbers of species inhabiting the various habitat types differed from the number to be expected on the basis of their area. This was especially apparent in the case of wetlands, which constituted only a small part of the total area, but as many as 32 species (21.1% of all) occurred only there. For conservation purposes, wetlands appear to play the most important role in shaping species richness in the landscape studied here. However, each habitat type contained some species that were not noted in other habitats.