Effect of nestling history on adult size and reproduction in the Great Tit

Abstract

I found a heritable variation of about 60% in the tarsus length of Great Tits in two populations, breeding in different (urban and rural) habitats of south-east Estonia. In spite of high heritability, the size of fledglings was also sensitive to growth conditions . Young from broods where nestling mortality occurred developed shorter tarsi compared to broods where all hatchlings fledged. Phenotypic variation in size was also remarkable among breeders . Cohorts of adults, born in poor breeding years had shorter tarsi than those born in normal years. Small females tended to lay small clutches which is consistent with the hypothesis that poor nestling history may have a lasting effect on the condition of breeding females and affect clutch size. I could not establish significant differences between populations in any of the aspects studied.