EFFECT OF NESTLING HISTORY ON ADULT SIZE AND REPRODUCTION IN THE GREAT TIT

I found a heritable variation of about 60% in the tarsus length of Gre at Tits in two populations, breeding in different (urban and rural) ha bitats of south-east Estonia. In spite of high heritability, the size of fledglings was also sensitive to growth conditions. Young from broo ds where nestling mortality occurred developed shorter tarsi compared to broods where all hatchlings fledged. Phenotypic variation in size w as also remarkable among breeders. Cohorts of adults, born in poor bre eding years had shorter tarsi than those born in normal years. Small f emales tended to lay small clutches which is consistent with the hypot hesis that poor nestling history may have a lasting effect on the cond ition of breeding females and affect clutch size. I could not establis h significant differences between populations in any of the aspects st udied.