Development and maintenance of nestling size hierarchies in the European starling (Sturnus vulgaris)

Abstract:
In this paper we show that nestling mass hierarchies in the European Starling (Sturnus vulgaris) are due to asynchronous hatching. The parents may, by starting to incubate the day the penultimate egg is laid, or earlier, affect the degree of hatching asynchrony and thereby the nestling weight hierarchy. Intra-clutch variation in egg size had no effect on nestling weight hierarchies, explaining only 0.4% of the variation 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 affected the variation in mass at least until nine days. This relationship was stronger in larger broods.