A SOCIO-ECOLOGY OF MAGPIES PICA PICA

The behaviour and ecology of unmarked Magpies Pica pica living in the Cotswolds were investigated over 18 months. The spacing of nests was significantly more regular than random and breeding pairs defended territories throughout the year. In winter pairs occasionally left territories to feed with non-breeding birds which flocked throughout the year.
Magpies in flocks had a higher averiage feeding rate than birds alone or in pairs. Aggression rates in flocks increased as birds fed closer together and as food patches became richer.
Agonistic interactions between Crows Corvus corone and Magpies were common; Crows frequently dominated Magpies in disputes over food, and Crows also ate Magpie eggs and young. Single Magpies were most often chased by Crows while Magpies in flocks were able to feed longer in the presence of Crows.
Differences in fledgling success among breeding pairs were related to the location of nests; Magpie pairs breeding near Crow nests suffered higher rates of agonistic encounters with Crows and also produced fewer fledglings than did Magpies breeding at greater distances from Crow nests. Magpie nests were located nearer human habitations than were Crow nests.