DEVELOPMENT AND MAINTENANCE OF NESTLING SIZE HIERARCHIES IN THE EUROPEAN STARLING

In this paper we show that nestling mass hierarchies in the European S tarling (Sturnus vulgaris) are due to asynchronous hatching. The paren ts may, by starting to incubate the day the penultimate egg is laid, o r earlier, affect the degree of hatching asynchrony and thereby the ne stling weight hierarchy. Intra-clutch variation in egg size had no eff ect on nestling weight hierarchies, explaining only 0.4% of the variat ion in nestling mass at two days of age. Nestlings kept their relative size to siblings throughout a substantial part of the nestling period . Furthermore, the degree of variation in mass at two days of age affe cted the variation in mass at least until nine days. This relationship was stronger in larger broods.