A Study of Life History of Blue Magpie (11)

Breeding Herpers and Nest-parasitism by Cuckoo

Abstract

An ecological survey of Cyanopica cyana was conducted from 1976 to 1980 in Hikage, Kinasa district (west part), Kamiminochi County, Nagano Prefecture. In this village it is resident through the year, even in winter with 1-1.5m of snowfall from December to April. Its maximum flock size ranged from 40-45 birds. Six nests were found within an area of 4km×0.3-0.8km and two were found 3.5km from the flock home range (non-breeding season wandering area). It nested in fir, Japanese cedar, Kaizukaibuki and Japanese apricot, and eggs were laid between early June and mid July, the clutch size being 6-7 and in three nests 1-2 eggs were left unhatched. One nest was parasitized by Cuckoo (Cuculus canorus). The Cuckoo chick, though it pushed out the Blue Magpie's eggs and a chick, starved because parent Blue Magpies abandoned the nest. Kenji Kobayashi reported to me four other cases, but only one nest was successful, in which chicks of both species, Blue Magpie and Cuckoo, fledged. During the feeding period, "helper behavior" by an individual hatched in the previous year was observed, which included feeding to chicks and females, taking away faeces and attacking enemies, etc.