THE INFLUENCE OF SIBLING GENDER ON THE GROWTH AND SURVIVAL OF GREAT-TAILED GRACKLE NESTLINGS

Predicted that, for Quiscalus mexicanus 1) the growth rates of nestlings would be lower in nests containing mostly males, and 2) the chance of all nestlings in predominantly male broods fledging would be less than that in predominantly female broods. Sibling gender and the overall sex ratio of the brood had little effect on nestling growth. There was no evidence that starvation was more frequent if the oldest nestlings were males rather than females, although there was some evidence that broods of 3 containing 2 or 3 males were less likely to fledge all nestlings than those containing 2 or 3 females. Mass at fledging for both males and females was influenced most strongly by hatching sequence and to a lesser extent by egg mass and hatching date. -from Author