Characteristic Features of Group Living Life of the Azure-winged Magpie Cyanopica cyana

Abstract

1) The social system of Azure-winged Magpies Cyanopica cyana was studied at Hizume, Nagano City, from 1983 to 1984, and at Kawanakajima, Nagano City, from 1962 to 1965 and inwinter of 1983.2) The six months from April to September were defined as the breeding season, because pairs with or without their fledglings were observed during this period.3) In the non-breeding season, flocks consisting of about 20 magpies were formed and the size of each flock was stable throughout the day.4) In the non-breeding season, all members of a flock always roosted together. In winter and spring, different flocks sometimes roosted together without any antagonistic behavior.5) The home range of Hizume flock was 1.2 km long and 0.9 km wide, and included 18 units of premises consisting of some houses and surrounding woods. Magpies spent longer time in premises with closed woods than those with sparse woods.6) Home ranges of flocks seemed to coincide nearly with territories, because the home ranges overlapped little with each other and chases were observed around the boundaries of the ranges.7) Flocks broke up into some pairs, non-breeding adults and subadults in the breeding season. At Hizume, nests of pairs belonging to the same winter flock were built 10-20 m apart from each other in a unit of premises, and the flock members visited the nests without any antagonistic behavior.8) The fledging rate was nearly 50%. Families consisting of pairs and their fledglings were observed from mid-May to mid-September. Family members moved and roosted together in the nesting woods about one month after fledging.9) There was no antagonistic behavior between families of the same flock. Some adults which had failed in breeding joined families, and one subadult fed fledglings as a helper.10) Even in the breeding season, not only pairs but also some non-breeding adults and subadults of the same flock sometimes moved or roosted together. They showed defensive behavior against conspecific intruders or natural enemies such as domestic cats and crows.11) As a conclusion of comparison among group-living birds, the Azure-winged Magpie was considered as a typical species which formed stable flocks throughout the year.