Abstract
Sperm cells from homozygous rose comb (RR) males were unable to compete with those from heterozygous (Rr) males when equal numbers of cells from the 2 types of males were pooled and artificially inseminated. In natural mating, RR males sired 15% of the chicken when mating competition with Rr males was low, but they sired only 7% of the chicks when mating competition was high.