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Wind-dependent foraging flight in the Osprey Pandion haliaetus

Author:
  • Roine Strandberg
  • Thomas Alerstam
  • M Hake
Publishing year: 2006
Language: English
Pages: 150-163
Publication/Series: Ornis Svecica
Volume: 16
Issue: 3
Document type: Journal article
Publisher: Sveriges Ornitologiska Förening

Abstract english

We studied the foraging technique of Ospreys Pandion haliaetus during different wind speed conditions at Lake Hammarsjon, Sweden in autumn 2003. Different fishing techniques were used with a shift in relation to wind speed: (1) without hovering, (2) hovering with pure flapping flight, (3) hovering with flapping flight and gliding into the wind, and (4) hovering with pure gliding. The results supported our predictions that hovering is constrained at low wind speeds and gliding restricted to wind speeds exceeding 7 m/s. Mixing flapping and gliding flight when hovering may be done as a trade-off between increased fishing efficiency associated with flapping flight and energy-saving combined with gain in total hovering time associated with gliding intervals. The relationship between hovering time and wind speed differed significantly between males and females. At wind speeds up to about 3.0 m/s, the hovering time increased more steeply with increasing wind speed for males than for females. In contrast, hovering time was shorter for males than for females at high wind speeds. The juveniles showed a lower mean, smaller scatter, and less increase in hovering time along the wind speed gradient.

Keywords

  • Biological Sciences

Other

Published
  • ISSN: 1102-6812
Thomas Alerstam
E-mail: thomas.alerstam [at] biol.lu.se

Professor emeritus

Evolutionary ecology

+46 46 222 37 85

E-C225

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Centre for Animal Movement Research
Evolutionary Ecology, Department of Biology
Ecology building S-223 62 Lund Sweden