HERITABILITY OF MIGRATORY ACTIVITY IN A NATURAL BIRD POPULATION

The presence of additive genetic variation is a prerequisite for changes in migratory behaviour through selection. Previous work with the blackcap, Sylvia atricapilla, has shown that the urge to migrate and the migratory direction are under genetic control. Here we examine whether migratory activity in this species has a significant additive genetic component, with the aim of predicting micro-evolutionary changes in migratory distance. Migratory activity was recorded in 280 southern German blackcaps from 69 families. We calculated heritabilities by parent-offspring regressions and by full-sibling correlations. Heritability estimates obtained by different methods were significantly different from zero and in good agreement with each other (k(2) = 0.37-0.46). This suggests that in the expression of migratory activity maternal and dominance effects are negligible. The high amount of phenotypic and additive genetic variation found for migratory activity in this population could lead to rapid evolutionary changes of migratory habits. Under moderate selection intensities and environmental conditions similar to those presented in this study, the southern German blackcap population could evolve into a short-distance migrant in 10-20 generations.