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Seasonal modulation of flight speed among nocturnal passerine migrants: differences between short- and long-distance migrants

Author:
  • Cecilia Nilsson
  • Johan Bäckman
  • Thomas Alerstam
Publishing year: 2014
Language: English
Pages: 1799-1807
Publication/Series: Behavioral Ecology and Sociobiology
Volume: 68
Issue: 11
Document type: Journal article
Publisher: Springer

Abstract english

Migrating birds are expected to fly at higher airspeeds when minimizing time rather than energy costs of their migratory journeys. Spring migration has often been suggested to be more time selected than autumn migration, because of the advantage of early arrival at breeding sites. We have earlier demonstrated that nocturnal passerine migrants fly at higher airspeeds during spring compared to autumn, supporting time-selected spring migration. In this study, we test the hypothesis that seasonal airspeeds are modulated differently between short- and long-distance migrants, because of a stronger element of time selection for autumn migration over long distances. In support of this hypothesis, we demonstrate that the seasonal difference in airspeed is significantly larger (spring airspeed exceeding autumn airspeed by a factor of 1.16 after correcting for the influence of altitude, wind and climb/descent on airspeed) among short-distance compared to long-distance (factor 1.12) migrants. This result is based on a large sample of tracking radar data from 3 years at Falsterbo, South Sweden. Short-distance migrants also tend to fly with more favourable winds during autumn, indicating relaxed time constraints (being able to afford to wait for favourable winds) compared to long-distance migrants. These results indicate surprisingly fine-tuned seasonal modulation of airspeed and responses to wind, associated with behavioural strategies adapted to different levels of time selection pressures during spring and autumn migration.

Keywords

  • Biological Sciences

Other

Published
  • CAnMove
  • ISSN: 1432-0762
Thomas Alerstam
E-mail: thomas.alerstam [at] biol.lu.se

Professor emeritus

Evolutionary ecology

+46 46 222 37 85

E-C225

Sölvegatan 37, Lund

50

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