Genetic Determination of Partial Migration in the European Robin (Erithacus rubecula)

Partially migratory behavior, the occurrence of resident and migratory individuals in a population, has been reported in free-living birds. I examined this behavior in the European Robin (Erithacus rubecula) under controlled experimental conditions. In an offspring group from a partially migratory field population, 36 (78%) individuals exhibited migratory restlessness (migrants), whereas 10 did not (residents). There were more migrants (89%) in an offspring group from exclusively migratory parents and fewer migrants (53%) from an offspring group from mostly resident parents than there were in the field population. A heritability value of 0.52 was found under the experimental conditions. A connection between the genetic determination of migratory behavior and unpredictable winter weather in the breeding area is discussed.