MICROEVOLUTIONARY ASPECTS OF BIRD MIGRATION BASED ON EXPERIMENTAL RESULTS

ABSTRACT

In many parts of the world we observe conspicuous changes in avian migratory habits. Alterations in migratoriness, mainly reductions, changes of migration times (particularly, later departures from and earlier returns to breeding grounds), and developments of novel migration routes and wintering areas are most obvious. It is likely that many of these changes are based on microevolutionary processes, i.e., selection. In a songbird population the rapid microevolution of a shift in the migratory direction of at least 30° within 30 years was established experimentally. With respect to changes in migratoriness, selection experiments with partial migrants show that shifts from full migratoriness to almost complete sedentariness are possible within 10 generations. Heritability estimates and other data also suggest rapid microevolutionary changes in migration distances and periods.