Egg-size variation in Yellow Warblers: apportionment of parental investment and the brood-survival hypothesis

Abstract

It has been hypothesized that in passerine birds the larger size of last-laid eggs is part of a brood-survival strategy. We examined the usefulness of the brood-survival hypothesis in explaining intraclutch variation in egg mass of Yellow Warblers (Dendroica petechia). In 4- and 5-egg clutches, egg mass increased significantly with laying order. Although last-hatched nestlings in broods of 4 had higher survival rates than their counterparts in broods of 5, there were no differences in the absolute or relative mass of last-laid eggs in clutches of 4 and 5 eggs. In addition, the mass of last-laid eggs that hatched but did not produce a fledgling was not significantly different from that of last-laid eggs that did produce a fledgling. Finally, the relative mass of last-laid eggs was also not correlated with hatch spread or with date of clutch initiation. The results of this study do not support the brood-survival hypothesis.