Sperm precedence in the domestic fowl

The aim of this study was to examine last-male sperm precedence in the domestic fowl. We used sperm from two different genotypes to assign paternity: and in seven experiments females were artificially inseminated with either equal or unequal numbers of sperm at intervals of 4 or 24 h. We were unable to replicate the results of a previous study by Compton et al. (1978) in which a strong last-male precedence effect had been recorded when two equal sized inseminations were made 4 h apart. We observed no marked last-male sperm precedence and our results did not differ significantly from that predicted by the passive sperm loss model, in which a last-male effect is determined by the rate at which sperm are lost from the female tract and the interval between successive inseminations. The most likely explanation for the disparity between our result and Compton et al.'s is a difference in the timing of inseminations. The implications of this for studies of sperm competition in birds is discussed.