Meeting Abstract

33.6  Jan. 5  Growth and survival consequences of ovulation order among sibling Lincoln’s sparrows SOCKMAN, K.W.*; Univ. of North Carolina, Chapel Hill kws@unc.edu

The asynchronous production of offspring may affect offspring viability, due to a potential sibling hierarchy established by competing siblings of unequal age and due to variation in parental provisioning relative to ovulation order. Using a population of free-living Lincoln’s sparrows (Melospiza lincolnii) breeding in a subalpine meadow near Molas Pass, Colorado, USA, I examined the growth and survival consequences of ovulation order among sibling nestlings. Ovulation order almost perfectly predicted hatching order, thus enabling the use of hatching order to infer ovulation order. Although I found no evidence that either egg volume or hatchability were related to ovulation order, ovulation order strongly influenced nestling survival, with survival of late-ovulated offspring much lower than that of early-ovulated offspring. Late ovulated offspring that survived to approximately fledging were lighter than their earlier ovulated siblings, and this was due to differences in nestling growth rate and possibly hatching mass. Regardless of their adaptive significance for the parents, these growth and survival consequences of ovulation order would seem to have strong implications on the relationship between sibling ovulation order and fitness and raise the possibility that one major source of fitness variation among individuals may stem from ovulation order.