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Twilight ascents by common swifts, Apus apus, at dawn and dusk: acquisition of orientation cues?

Dokter, Adriaan M. ; Åkesson, Susanne LU ; Beekhuis, Hans ; Bouten, Willem ; Buurma, Luit ; van Gasteren, Hans and Holleman, Iwan (2013) In Animal Behaviour 85(3). p.545-552
Abstract
Common swifts are specialist flyers spending most of their life aloft, including night-time periods when this species roosts on the wing. Nocturnal roosting is preceded by a vertical ascent in twilight conditions towards altitudes of up to 2.5 km, behaviour previously explained as flight altitude selection for sleeping. We examined the nocturnal flight behaviour of swifts, as uniquely identified by a Doppler weather radar in central Netherlands using continuous measurements during two consecutive breeding seasons. Common swifts performed twilight ascents not only at dusk but also at dawn, which casts new light on the purpose of these ascents. Dusk and dawn ascents were mirror images of each other when time-referenced to the moment of... (More)
Common swifts are specialist flyers spending most of their life aloft, including night-time periods when this species roosts on the wing. Nocturnal roosting is preceded by a vertical ascent in twilight conditions towards altitudes of up to 2.5 km, behaviour previously explained as flight altitude selection for sleeping. We examined the nocturnal flight behaviour of swifts, as uniquely identified by a Doppler weather radar in central Netherlands using continuous measurements during two consecutive breeding seasons. Common swifts performed twilight ascents not only at dusk but also at dawn, which casts new light on the purpose of these ascents. Dusk and dawn ascents were mirror images of each other when time-referenced to the moment of sunset and sunrise, suggesting that the acquisition of twilight-specific light-based cues plays an important role in the progression of the ascents. Ascent height was well explained by the altitude of the 280 K isotherm, and was not significantly related to wind, cloud base height, humidity or the presence of nocturnal insects. We hypothesize that swifts profile the state of the atmospheric boundary layer during twilight ascents and/or attempt to maximize their perceptual range for visual access to distant horizontal landmarks, including surrounding weather. We compare twilight profiling by swifts with vertical twilight movements observed in other taxa, proposed to be related to orientation and navigation. (C) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. (Less)
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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Apus apus, atmospheric assessment, celestial cue, common swift, flight, altitude, orientation, navigation, twilight, weather radar
in
Animal Behaviour
volume
85
issue
3
pages
545 - 552
publisher
Elsevier Ltd
external identifiers
  • wos:000315794400006
  • scopus:84875243282
ISSN
1095-8282
DOI
10.1016/j.anbehav.2012.12.006
project
Centre for Animal Movement Research
language
English
LU publication?
yes
id
0ca50830-4800-42a8-a035-35e500098a00 (old id 3669964)
date added to LUP
2016-04-01 10:29:22
date last changed
2021-01-27 22:02:14
@article{0ca50830-4800-42a8-a035-35e500098a00,
  abstract     = {Common swifts are specialist flyers spending most of their life aloft, including night-time periods when this species roosts on the wing. Nocturnal roosting is preceded by a vertical ascent in twilight conditions towards altitudes of up to 2.5 km, behaviour previously explained as flight altitude selection for sleeping. We examined the nocturnal flight behaviour of swifts, as uniquely identified by a Doppler weather radar in central Netherlands using continuous measurements during two consecutive breeding seasons. Common swifts performed twilight ascents not only at dusk but also at dawn, which casts new light on the purpose of these ascents. Dusk and dawn ascents were mirror images of each other when time-referenced to the moment of sunset and sunrise, suggesting that the acquisition of twilight-specific light-based cues plays an important role in the progression of the ascents. Ascent height was well explained by the altitude of the 280 K isotherm, and was not significantly related to wind, cloud base height, humidity or the presence of nocturnal insects. We hypothesize that swifts profile the state of the atmospheric boundary layer during twilight ascents and/or attempt to maximize their perceptual range for visual access to distant horizontal landmarks, including surrounding weather. We compare twilight profiling by swifts with vertical twilight movements observed in other taxa, proposed to be related to orientation and navigation. (C) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.},
  author       = {Dokter, Adriaan M. and Åkesson, Susanne and Beekhuis, Hans and Bouten, Willem and Buurma, Luit and van Gasteren, Hans and Holleman, Iwan},
  issn         = {1095-8282},
  language     = {eng},
  number       = {3},
  pages        = {545--552},
  publisher    = {Elsevier Ltd},
  series       = {Animal Behaviour},
  title        = {Twilight ascents by common swifts, Apus apus, at dawn and dusk: acquisition of orientation cues?},
  url          = {http://dx.doi.org/10.1016/j.anbehav.2012.12.006},
  doi          = {10.1016/j.anbehav.2012.12.006},
  volume       = {85},
  year         = {2013},
}