Ardea
Official journal of the Netherlands Ornithologists' Union

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Strandberg R., Klaassen R.H.G., Olofsson P. & Alerstam T. (2009) Daily travel schedules of adult Eurasian Hobbies Falco subbuteo variability in flight hours and migration speed along the route. ARDEA 97 (3): 287-295
We analysed satellite tracking data to reveal the daily travel schedules of Hobbies Falco subbuteo migrating between northern Europe and southern Africa. By comparing movements during short-time intervals of 18 h at different times of the day between the three different regions Europe, Sahara Desert and tropical Africa, we found significant higher hourly speeds in the Sahara compared to the other two regions. The migration started early in the morning and continued throughout the day, resulting in daily travel time exceeding that of typical thermal soaring migrants. Due to fast hourly speeds in combination with the long travel days during Sahara crossings, the Hobbies exceeded daily travel distances recorded for soaring migrants. In Europe and tropical Africa, the speed was highly variable during the day, and lower flight speeds, especially during afternoons, suggest a fly-and-forage strategy. Our predictions about regular occurrence of nocturnal flight especially across geographical barriers as the desert were not fulfilled. In the Sahara, the Hobbies restricted their movement to diurnal migration. Nevertheless, 10% of the flight segments in tropical Africa were partly or completely during night hours and Hobbies often started their daily flight before or at sunrise. We attribute the special characteristics of the daily travel schedules of Hobbies primarily to their use of a fly-and-forage strategy, possibly in combination with preparedness for exploiting thermals during the daily thermal time window. Further studies are needed to understand why Hobbies do not increase daily travelling hours to include regular nocturnal flight in the Sahara Desert. We suggest that the daily travel schedules of the Hobby, which were distinctly different from those of other diurnal migrants like large raptors (which mainly exploit thermal soaring migration) or pipits, wagtails, finches and pigeons (which mainly travel during the morning hours) may be typical for bird species that primarily use a fly-and-forage migration strategy.


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