Feb. 21, 2013 — Common swifts climb to altitudes of up to 2.5 km both at dawn and dusk. This unexpected behaviour was discovered by geo-ecologist Dr Adriaan Dokter of the University of Amsterdam's (UvA) Institute for Biodiversity and Ecosystem Dynamics (IBED) together with colleagues from the Royal Netherlands Meteorological Institute (KNMI), the Royal Netherlands Air Force and Lund University.
The research results were published as a featured article in the March issue of the scientific journal Animal Behaviour.
In the summer, swifts make their presence felt in the city, especially because of the screaming sound they make. These common urban birds appear to have unusual movement patterns. Besides a short breeding period under urban roofing tiles, these birds spend all year on the wing: foraging, mating and even sleeping are all performed in flight. Using a novel radar technique, Dokter and his colleagues studied the nocturnal flight behaviour of the common swift with the assistance of a weather radar belonging to the KNMI.
Dokter explains: 'We always assumed that common swifts ascended in the evening as part of their sleeping cycle. However, now that we have observed the bird perform ascents at both the start and the end of night-time periods, this interpretation seems to be incorrect. The ascents must have a different function, with the birds making use of the unique opportunities offered by the twilight period.'