Young avian migrants of many species are able to find their species-specific or population-specific wintering area without the help of conspecifics. In orientation tests hand-raised birds have been demonstrated to choose appropriate population-specific migratory directions, suggesting a genetic basis to this behavior.
I here report results of a cross-breeding experiment between individuals of 2 blackcap (Sylvia atricapilla) populations with widely different migratory directions. The orientation of the F1 offspring was intermediate between and statistically-significantly different from that of both parental populations (Figure 2). The variance of individual mean directions in the F1 generation did not increase compared with the parental groups, and the inheritance of migratory directions was not sex-linked.
The data provide direct evidence for a genetic basis of migratory directions in birds and demonstrate a phenotypically intermediate mode of inheritance.
