Different bird strategies and their responses to habitat changes in an agricultural landscape


*Email: tworek@iop.krakow.pl


Breeding bird communities were investigated in habitat islands in the agricultural landscape of southern Poland in 1995–1998. Using the following species-specific characteristics of birds – type and location of nest, type of food, place and way of foraging, type of migration, clutch size, incubation period, fledging period and number of broods per year – five typical bird strategies were delimited: ‘terrestrial’, ‘predators’, ‘hole-nesters’, ‘vagrants’ and ‘arboreal’. Stepwise multiple regression and canonical correlation analyses were used to examine relationships between ecological parameters for bird strategies and habitat variables describing sample plots. Bird densities, domination, species abundance and turnover rates depended on the area and structure of a habitat island and to a lesser extent on isolation and surrounding land use. Terrestrial birds tend to occupy large, open habitats, often wetlands, predators also need extensive areas of forest for nesting and open habitats for foraging, hole-nesters demand areas with old tree stands or other places where they can hide their nests, many close to human settlements, vagrants prefer dampish habitats with rich herb and shrub layers and arboreal birds appear to be characteristic of forest edges. Results from this study show that responses of birds to habitat changes differ depending on their strategies. Some life styles benefit from habitat fragmentation, while for others it is a principal threat. The methodology used in this study can be a model for species that share distributional, ecological or life-history features and may enable more effective conservation of bird species.