Genetic variation is linked to differences in migration timing in wild American kestrels. The image shows findings from genetic analyses of feathers or small blood samples of the birds. (a) An overview analysis of genes with possible links to timing illustrates how the genes covary in all genotyped birds. (b) Variation in some of these genes, together, can explain a great proportion of timing differences. This high explanatory power has been confirmed for individual kestrels migrating through Idaho during autumn migration; from Bossu et al. 2022, https://royalsocietypublishing.org/doi/10.1098/rspb.2021.2507