NUTRITIONAL ADAPTATIONS IN MIGRATING BIRDS

Prior to migration, many birds accumulate large stores of lipids as the primary energy for their migratory flights. Fat accumulation is associated with a seasonal shift in food selection, an increase in premigratory daily food intake, and an increase in utilization efficiency of ingested food. Seasonal frugivory is the most striking seasonal change in diet composition of many migrants. The adaptive role of seasonal facultative frugivory has only rarely been investigated. Fruits seem to provide a particular nutritional quality, namely fatty acids, which promote the accumulation of premigratory fat of a particular quality. Moreover, plant secondary compounds seem to play a role in migratory fat accumulation, and there is evidence that several plant allelochemicals that are consumed with the fruits increase appetite and stimulate tissue anabolism. The nutritional mechanisms, however, are as yet unknown.