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Compensation for wind drift by migrating swifts

Karlsson, Håkan LU ; Henningsson, Per LU ; Bäckman, Johan LU ; Hedenström, Anders LU and Alerstam, Thomas LU (2010) In Animal Behaviour 80(3). p.399-404
Abstract
We investigated the orientation in relation to wind of common swifts, Apus apus, during nocturnal spring and autumn migration. Swifts are highly adapted to a life in the air, showing wind-dependent orientation during nocturnal roosting flights, and may be expected to be more efficient in their wind drift/compensation behaviour than nocturnal passerine migrants, which are usually subjected to full or partial wind drift. A tracking radar at Lund in southern Sweden was used to record the orientation of common swifts (identified by their characteristic radar echo signature) on nocturnal migration flights and to measure wind conditions at the altitudes at which the birds were flying. Comparing track and heading directions under easterly and... (More)
We investigated the orientation in relation to wind of common swifts, Apus apus, during nocturnal spring and autumn migration. Swifts are highly adapted to a life in the air, showing wind-dependent orientation during nocturnal roosting flights, and may be expected to be more efficient in their wind drift/compensation behaviour than nocturnal passerine migrants, which are usually subjected to full or partial wind drift. A tracking radar at Lund in southern Sweden was used to record the orientation of common swifts (identified by their characteristic radar echo signature) on nocturnal migration flights and to measure wind conditions at the altitudes at which the birds were flying. Comparing track and heading directions under easterly and westerly winds revealed that the swifts shifted their heading distinctly into the wind, with the result that track directions were similar under the different wind conditions. As this pattern of complete compensation for drift from cross-winds occurred during both spring and autumn migration, there were no indications of differences between age classes. In addition, we found an effect of side-winds on equivalent airspeeds, with swifts increasing their airspeed with increasing wind speed. Such a response has been theoretically predicted as part of an optimal behaviour for counteracting wind drift but has hereto not been empirically demonstrated. There was also a positive correlation between overall wind speed and equivalent airspeed, making it difficult to interpret whether the swifts respond to the total wind speed rather than specifically to the side-wind effect. Our results suggest that important differences may exist between species in their capacities to orient in relation to the wind and that the swift may be particularly efficient in adjusting heading direction and airspeed to obtain complete compensation for wind drift during high-altitude nocturnal migratory flights. (C) 2010 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
wind, tracking radar, side-wind, orientation, migration, drift, compensation, Apus apus, common swift
in
Animal Behaviour
volume
80
issue
3
pages
399 - 404
publisher
Elsevier Ltd
external identifiers
  • wos:000280846800007
  • scopus:77955583038
ISSN
1095-8282
DOI
10.1016/j.anbehav.2010.05.023
project
CAnMove
language
English
LU publication?
yes
id
d14c6264-9def-4162-9550-062e54b8274c (old id 1677202)
date added to LUP
2010-09-21 15:42:26
date last changed
2018-05-29 12:27:21
@article{d14c6264-9def-4162-9550-062e54b8274c,
  abstract     = {We investigated the orientation in relation to wind of common swifts, Apus apus, during nocturnal spring and autumn migration. Swifts are highly adapted to a life in the air, showing wind-dependent orientation during nocturnal roosting flights, and may be expected to be more efficient in their wind drift/compensation behaviour than nocturnal passerine migrants, which are usually subjected to full or partial wind drift. A tracking radar at Lund in southern Sweden was used to record the orientation of common swifts (identified by their characteristic radar echo signature) on nocturnal migration flights and to measure wind conditions at the altitudes at which the birds were flying. Comparing track and heading directions under easterly and westerly winds revealed that the swifts shifted their heading distinctly into the wind, with the result that track directions were similar under the different wind conditions. As this pattern of complete compensation for drift from cross-winds occurred during both spring and autumn migration, there were no indications of differences between age classes. In addition, we found an effect of side-winds on equivalent airspeeds, with swifts increasing their airspeed with increasing wind speed. Such a response has been theoretically predicted as part of an optimal behaviour for counteracting wind drift but has hereto not been empirically demonstrated. There was also a positive correlation between overall wind speed and equivalent airspeed, making it difficult to interpret whether the swifts respond to the total wind speed rather than specifically to the side-wind effect. Our results suggest that important differences may exist between species in their capacities to orient in relation to the wind and that the swift may be particularly efficient in adjusting heading direction and airspeed to obtain complete compensation for wind drift during high-altitude nocturnal migratory flights. (C) 2010 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.},
  author       = {Karlsson, Håkan and Henningsson, Per and Bäckman, Johan and Hedenström, Anders and Alerstam, Thomas},
  issn         = {1095-8282},
  keyword      = {wind,tracking radar,side-wind,orientation,migration,drift,compensation,Apus apus,common swift},
  language     = {eng},
  number       = {3},
  pages        = {399--404},
  publisher    = {Elsevier Ltd},
  series       = {Animal Behaviour},
  title        = {Compensation for wind drift by migrating swifts},
  url          = {http://dx.doi.org/10.1016/j.anbehav.2010.05.023},
  volume       = {80},
  year         = {2010},
}