First evidence on migratory restlessness in a species of birds of prey (Honey Buzzard, Pernis apivorus)

Drei zugunerfahrene Wespenbussarde wurden nach zehn- bzw. zwölfjähriger Volierenhaltung unter mitteleuropäischen Naturtagbedingungen in Bezug auf ihr jahresperiodisches Verhalten untersucht. Registriert wurde die Flugaktivität von zwei Weibchen. Zusätzlich wurde an diesen und einem Männchen die individuelle Körpermasse im Jahresverlauf aufgezeichnet. Der Anstieg der Flugaktivität mit einem signifikanten Anteil im Oktober wird als Zugunruhe gedeutet. Die Wespenbussarde entwickelten eine deutliche Herbstzugdisposition mit individuellen Charakteristiken im zeitlichen Ablauf. Das jahresperiodische Verhalten nach der langen Volierenhaltung unter falscher Fotoperiode im Winter ist ein Indiz für das Vorliegen einer endogenen Rhythmik.After 10 resp. 12 years of being caged in an outdoor aviary exposed to central European environmental conditions, 3 Honey Buzzards’ seasonal behaviour was studied. The Honey Buzzards had no previous migratory flight experience. All measurements were taken in the outdoor aviary. Recorded was the flight activity of 2 females using a light brake. Their individual body mass was also recorded and a third Honey Buzzard (male)’s measurements were taken as well. The flight activity increased significantly in October. During this time the Honey Buzzards also showed other restless behaviour such as excited looking around and flapping their wings on the seat. This behaviour and the annual increase of flight activity is interpreted as migratory restlessness, which is the first evidence of this behaviour on a bird of prey. Also a roosttime restlessness (for definition see Berthold 1988) was ascertained. It depends on seasons, especially between November and February. The Honey Buzzards developed a positive autumn migratory disposition (fat deposition). The mass of fattening during the autumn migratory period is within the range of wild conspecifics. The temporal fattening and breakdown of fat deposition shows individual characteristics. As the photoperiod controls the fat deposition, these details and the migratory restlessness even after the long time being exposed to the “wrong” winter photo period conditions could be indications of endogenous rhythms on the Honey Buzzard