The role of hatching asynchrony in brood size reduction of the great tit Parus major in a Mediterranean pine forest

摘要

The breeding biology of the great tit Parus major in a Pinus brutia forest was studied. Asynchrony of hatching has been proposed as a mechanism to decrease "surplus'' nestlings depending on the availability of food. Asynchrony drives nestlings that will die anyway, to die as early as possible, so that they will not consume food which would be utilized by the rest of the nestlings with higher surviving probabilities. The main question of this paper is whether asynchrony is indeed an adaptive strategy that increases the survival probability and quality of the surviving nestlings. To see whether patterns of brood reduction are consistent with the above hypothesis the following were examined: a) the incidence of brood reduction in the population, b) whether the nestlings that die are actually the latest-hatched ones and c) whether nestlings that die do so at an early age.