Population increase and breeding ecology of the Varied Tit Parus varies in a secondary forest with nest boxes

Abstract

The breeding ecology of the Varied Tit Parus varius was studied without nest boxes for two years and with nest boxes for ten years, at an eight ha. Secondary forest, with very few natural cavities, in central Japan. The breeding population consisted of only one pair each in the first two years. After setting out nest boxes, eight pairs bred in the first year and pro-duced 15 to 22 clutches in the following nine years. There was no relation-ship between the numbers of early and late broods in each year. Egg laying had a larger peak in frequency in early April and a smaller peak in mid-May. The starting day of nest building and the first egg-laying day significantly correlated to the January-March temperature. The length of incubation and fledging periods did not significantly correlate to brood size. Hatching success seemed to be higher in larger clutches. There was no significant correlation between number of nestlings and the length of nestling periods. The number of fledged young was significantly larger at eight nests of larger clutch size. Clutch sizes were significantly larger in early (6.35) than late (5.98) seasons. In successful nests, with one or more fledged young, more young fledged at the nests with larger clutches. Mean nest density was 1.63/ha, and many pairs foraged out of the research (nest) area. Mean distance between nests was 56 m and the closest two was 15m away from each other. New nest boxes were preferred significantly more, and such behavior seemed adaptive to escape nest predation.