The Visual Problems of Nocturnal Migration

Abstract

Amongst birds a completely nocturnal life-style is rare. Less that 1% of species habitually complete all aspects of their life-cycle outside of daylight hours. However, occasional nocturnal activity in otherwise diurnal birds is relatively common. The most widespread such behaviour is migration at night (Martin 1990). How diurnal birds cope with occasional nocturnal activity is not well understood, but in view of the restricted life-style of truly nocturnal birds (Martin 1986a), it is perhaps surprising to find that otherwise strictly diurnal birds are able to undertake their migratory flights at night.