Heritability of arrival date in a migratory bird

The behaviour of long-distance migratory birds is assumed to partly be unde r the influence of genes, as demonstrated by selection experiments. Further more, competition for early arrival among males may lead to condition-depen dent migration associated with fitness benefits of early arrival achieved b y individuals in prime condition. Here I present field data on the repeatab ility and the heritability of arrival date in a trans-equatorial migratory bird, the barn swallow Hirundo rustica, and I test for a genetic correlatio n between arrival date and the expression of a condition-dependent secondar y sexual character. The repeatability was statistically significant and the heritability of arrival date was estimated to be 0.54 (s.e. =0.15). There was no significant evidence of this estimate being inflated by environmenta l or maternal condition during rearing. Arrival date and migration are cond ition dependent in the barn swallow, with males with the most exaggerated s econdary sexual characters also arriving the earliest. There was a signific ant genetic correlation between arrival date and tail length in male barn s wallows, providing indirect evidence for a genetic basis of this condition dependence. Given the high level of heritability, arrival date could readil y respond to selection caused by environmental change.