PREDICTORS OF FERTILIZATION IN THE JAPANESE-QUAIL, COTURNIX JAPONICA

To better understand the relationship between mating behaviour, insemination and fertilization in birds, 233 mating trials were conducted with Japanese quail to determine the percentage of eggs laid that were fertile following a single confirmed or putative insemination. Fertilization success of single inseminations was highly variable. Insemination did not guarantee fertilization of any eggs; following one-third of the trials, no fertile eggs were laid. Only 3% of inseminations fertilized as many as eight eggs, making it unlikely that a single insemination could fertilize an entire clutch in this species. Forced copulations had the same fertilization success as other copulations, and thus could be a successful male reproductive strategy in this species. Voiding of foamy material containing sperm by the female shortly after copulation did not reduce fertilization success in any consistently significant manner. Fertilization success was unaffected by the presence of a hard-shelled egg in the uterus at the time of insemination. Trials in which the female ran from the male's initial approach resulted in fewer fertile eggs following insemination; that is, this behaviour predicted low fertilization success. Fertilization success was highly correlated and thus predictable if the same female was mated again with the same male, but was uncorrelated if she was mated with a different male or if the same male was mated with different females. These two predictors of fertilization success (female behaviour and male-female combination) are interpreted as evidence for female control of paternity via sperm selection (postcopulatory female choice). (C) 1995 The Association for the Study of Animal Behaviour