HATCHING ASYNCHRONY AND FEEDING RATES IN YELLOW WARBLERS - A TEST OF THE SEXUAL CONFLICT HYPOTHESIS

T. Slagsvold and J. T. Lifjeld have proposed that hatching asynchrony in bird species in which only the female incubates is a strategy used by females to extract more parental investment from their mates. We ex amined this hypothesis by comparing feeding rates of female and male y ellow warblers (Dendroica petechia) tending asynchronously and synchro nously hatched broods. Regardless of brood size, feeding rates during the early, middle, and late nestling periods were similar for females tending asynchronously and synchronously hatched broods. Nevertheless, there was a general trend for females tending asynchronous broods to have lower feeding rates, which suggests that females may prefer hatch ing asynchrony. This is consistent with the sexual conflict hypothesis . Male feeding rates exhibited trends similar to those of females. Tha t is, although the result is not statistically significant, males tend ing asynchronous broods, regardless of brood size, generally made fewe r feeds than males tending synchronously hatched broods. However, male s tending asynchronous broods of five did make significantly fewer fee ds during the early nestling period than males tending similar-sized s ynchronous broods. This was also true when the data were combined acro ss brood sizes. This suggests, contrary to the sexual conflict hypothe sis, that males, especially those tending larger broods, should favor hatching asynchrony. Consequently, the sexes do not appear to be in co nflict as to when incubation should begin, but rather females and male s prefer, or at the very least are neutral with respect to, the initia tion of incubation prior to clutch completion.