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.