Late-hatched Great Tits Parus major: How do they contribute to the next year breeding population?

Abstract

Late-hatched Great Tits Parus major have often a lower local recruitment rate than those hatched early. However, estimates of recruitment usually neglect differential disappearance due to dispersal. We report on the proportions of late-hatched breeders in two Great Tit breeding populations (near St. Petersburg, NW Russia, and on the Courish Spit, Eastern Baltic). Using a novel method, late-hatched birds (hatching in July) were distinguished in the next breeding season by the incomplete moult of their tail feathers. Based on this method, we were able to estimate the percentage of late-hatched individuals in all first-year birds, including immigrants. The proportion of late hatched breeders was considerable in some years, and appeared related to the proportion of late fledglings in the previous year. In the Courish Spit population we found no significant difference in the global recruitment rate (accounting for both local birds and immigrants) of early- and late-hatched Great Tits. In the St. Petersburg population, the annual percentage of late-fledged breeders was significantly lower than the percentage of late-hatched fledglings in the previous year. However, in the St. Petersburg population we cannot definitely conclude that the global recruitment rate of late fledglings was lower than that of early fledglings because of peculiarities of the study site. We also can suggest that it may be a result of competition between early and late fledglings, winter residents and newcomers in spring (especially in males), as well as a result of different survival of early- and late-born individuals during the first year.