Relationships between the abundance of breeding birds in Western Poland and the structure of agricultural landscape

The relationships between bird abundance and landscape structure were studi ed in nine plots located in an agricultural landscape in W Poland. Numbers of bird species per plot ranged from 3 to 31, densities from 3.8 to 32.8 pa irs/10 ha. Habitat parameters, as percentage of tree cover ranged from 0 to 14.5%, meadows from 0 to 48.5%, habitat diversity (H') from 0.004 to 1.07, density of forest - field ecotones from 0 to 144 m/ha, density meadows and crop field ecotones from 0 to 38 m/ha, and ecotones between crop fields - from 0 to 245 m/ha. The number of bird species per plot increased most sign ificantly with tree cover (r(2) = 0.63 in linear regression); the density o f breeding pairs also increased linearly with tree cover (r(2) = 0.85 in li near regression). Tree cover was also the main factor influencing the densi ty or species number of particular nesting-guilds with the exception of the density of ground-nesters, which was not significantly related to any 'hab itat' variable. The relationships between wood cover and species number app eared to be non-linear, showing higher slope values at smaller values of wo od cover. Protection of high bird abundance in western Poland is strongly l inked with the preservation of margin habitats, especially woodlots, which provide nesting opportunities for most of the species occurring in farmland in W Poland.