Sex Allocation in Corvus brachyrhynchos

by Loren Baldus
Faculty advisor: Dr. Richard Lampe

Sex allocation is a strategy used in many organisms, as there may be fitness advantages to producing more of one sex. In the case of cooperatively breeding species, biased production of the sexes may facilitate greater fitness returns if the population dynamics select for the sex with greater likelihood of breeding dispersal. The cooperatively breeding population of American Crows (Corvus brachyrhynchos) in Storm Lake was studied to determine whether the near-fledging sex ratio was biased. Based on evidence from the Ithaca, NY, population of crows, whose nestling ratios were unbiased, we expected similar results in our population of crows. During the 2008 and 2009 breeding seasons, we collected blood from over 100 late-stage nestlings and determined sex using molecular techniques. We will report on whether sex ratios were biased and whether local population pressures, including relatively high hunting rates, potentially influenced family- and population-level sex ratios.