Connections between predatory birds and mammals and their prey

An analysis was made of the diet, numbers and penetration of study area by a group of predators typical of the agrocenoses of the Wielkopolska region of Poland. There was distingguished a group of predators highly specialized in capture of the common vole.This group includes species for which the vole forms the most important component of their food, which react very markedly in respect of their numbers to variations in the density of rodent and which obtain their food chiefly in fields and meadows. Estimates are given of the extent of pressure exerted by predators on field and forest rodents, and means of counteracting mass irruption of field rodents discussed. Czteroletnie badania nad drapieżnymi ptakami i ssakami prowadzone przez okres pełnego cyklu zmian zagęszczenia nornika zwyczajnego w okolicach Turwi pozwoliły ocenić zmienność pokarmu, liczebności i penetracji terenu przez drapieżniki przy róznych liczebnościach nornika