Adaptive differences in the timing of egg laying between different populations of birds result from variation in photoresponsiveness

We estimated the number and quality of sperm that male peafowl (Pavo cristatus) transferred during copulation to examine differences in these features between males. Ejaculate size was estimated in two ways: directly from sexually rested males copulating with a stuffed female (mean number of sperm per ejaculate 124 $\times $ 10$^{6}$ $\pm $ 39.73 $\times $ 10$^{6}$ s.d.); and indirectly as the number of sperm on the outer perivitelline layers of laid eggs (1386 $\pm $ 116 s.d.). Neither method revealed any significant difference between males. The mean percentage of live sperm in ejaculates was 84% $\pm $ 12 s.d. (n = 6 males) and the number of live sperm per ejaculate was significantly and positively correlated with the number of sperm found on the outer perivitelline layers of eggs laid by females inseminated by those males. There was no significant difference between males in the proportion of live sperm per ejaculate. The instantaneous rate at which sperm were lost from the female tract was 0.0067 sperm h$^{-1}\pm $ 0.0008 s.e. and the mean duration of sperm storage was 26 days $\pm $ 8.6 s.e. (n = 9 females), both these values are intermediate between those found in other galliformes. Beacause neither of the two methods for estimating of the numbers of sperm per ejaculate size differed significantly between males, it seems unlikely that female peafowl could obtain reliable direct fertility benefits from choosing to copulate with particular males.