Brood reduction facilitates female but not offspring survival in the great tit.

The long-term fitness consequences of brood reduction were examined in two (urban and rural) great tit populations in south-eastern Estonia during 1987-1994. The brood reduction hypothesis in its initial, Lackian sense was not supported since partial brood loss was accompanied by a decrease in fledgling weight and recruitment rate. Female survival was significantly improved in broods with high nestling mortality in the rural population. My results suggest that female great tits might be able to reallocate resources for self-maintenance if food appears to be short for the successful raising of the brood. However, parents are not capable of efficiently reallocating resources between nestlings.