Nocturnal life of young songbirds well before migration

Abstract

In songbirds, nocturnal activity is believed to be a characteristic feature of migration. However, unlike experimental conditions where the onset of nocturnal restlessness is defined as a shift of activity leading up to the dark period, this behaviour has, until now, not been observed in natural conditions. Here we studied the nocturnal behaviour of radio-tagged juvenile Eurasian reed warblers (Acrocephalus scirpaceus) during the pre-migratory period. The birds started nocturnal flights at the age of 38 days, whereas migration did not commence until they were at least 50 days old. The birds left their natal site by nocturnal flights and repeatedly returned to it. Such shuttle movements suggest the existence of a previously unknown period of nocturnal activity. Motivation to perform such night flights gradually increases with age. We relate the function of these nocturnal pre-migratory flights to the development of a stellar compass, necessary for detecting the compass direction towards winter quarters and for the formation of a navigational target, which will be used during return (spring) migration.

How far do birds fly during one migratory flight stage?

“…Ellegren (1993) estimated the average flight time to be 3.3 hours a day for diurnal migrants and that the period spent flying during the night by nocturnal migrants was shorter than the length of the dark period (range 1-15 hours). Åkesson & Hedenström (2000) estimated the mean departure time for passerines from Öland, SE Sweden, to be one hour after sunset and Reed Warblers leaving Russia on autumn migration started night movements on average in the fourth hour of the night (Muhkin et al 2005). found a pronounced peak of migratory intensity during the first half of the night, indicating that birds begin to land after only 3-6 hours of flight.…”

Experimental identification of social learning in wild animals

“…The Banks and Guilford study has obvious relevance to any species whose members travel in groups and is particularly innovative, since animal movement patterns present many fascinating questions regarding potential traditions. For example, little is currently known about the precise role of social (and individual) learning, relative to genetically encoded direction preferences (Helbig, 1991;Mukhin, Kosarev, & Ktitorov, 2005;Plotkin, Byles, Rostal, & Owens, 1995) in the establishment, maintenance, and fine-tuning of migration routes in annual long-distance migrants that travel in mixed-age, mixed-sex, and mixed-experience groups. The fact that novel migration routes can evolve rapidly (Berthold, Helbig, Mohr, & Querner, 1992) reinforces the message that genetic adaptations may evolve quickly and should not be excluded as an explanation for the appearance of novel behavior patterns.…”

Sex-specific timing of mate searching and territory prospecting in the nightingale: nocturnal life of females

“…Studies investigating animal behaviour around the clock often reveal surprising temporal flexibility; for example, young reed warblers (Acrocephalus scirpaceus) regularly show nocturnal movements well before migration (Mukhin et al 2005) and golden hamsters (Mesocricetus auratus) are nocturnal in captivity but diurnal in nature (Gattermann et al 2008). Most behaviour is energy and time consuming, and the optimal daily routine is thought to be an adaptive compromise (Hutchinson et al 1993).…”