Data from: The genetic regulation of avian migration timing: combining candidate genes and quantitative genetic approaches in a long-distance migrant

Plant and animal populations can adapt to prolonged environmental changes
if they have sufficient genetic variation in important phenological
traits. The genetic regulation of annual cycles can be studied either via
candidate genes or through the decomposition of phenotypic variance by
quantitative genetics. Here we combined both approaches to study the
timing of migration in a long-distance migrant, the collared flycatcher
(Ficedula albicollis). We found that none of the four studied candidate
genes (CLOCK, NPAS2, ADCYAP1 and CREB1) had any consistent effect on the
timing of six annual cycle stages of geolocator-tracked individuals. This
negative result was confirmed by direct observations of males arriving in
spring to the breeding site over four consecutive years. Although male
spring arrival date was significantly repeatable (R = 0.24 ± 0.08), most
was attributable to permanent environmental effects, while the additive
genetic variance and heritability was very low (h2 = 0.03 ± 0.17 SE). This
low value constrains species evolutionary adaptation, and our study adds
to warnings that such populations may be threatened, e.g. by ongoing
climate change.