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Flight altitude dynamics of migrating European nightjars across regions and seasons

Norevik, Gabriel LU orcid ; Åkesson, Susanne LU ; Andersson, Arne LU orcid ; Bäckman, Johan LU orcid and Hedenström, Anders LU (2021) In Journal of Experimental Biology 224(20). p.1-1
Abstract

Avian migrants may fly at a range of altitudes, but usually concentrate near strata where a combination of flight conditions is favourable. The aerial environment can have a large impact on the performance of the migrant and is usually highly dynamic, making it beneficial for a bird to regularly check the flight conditions at alternative altitudes. We recorded the migrations between northern Europe and sub-Saharan Africa of European nightjars Caprimulgus europaeus to explore their altitudinal space use during spring and autumn flights and to test whether their climbs and descents were performed according to predictions from flight mechanical theory. Spring migration across all regions was associated with more exploratory vertical... (More)

Avian migrants may fly at a range of altitudes, but usually concentrate near strata where a combination of flight conditions is favourable. The aerial environment can have a large impact on the performance of the migrant and is usually highly dynamic, making it beneficial for a bird to regularly check the flight conditions at alternative altitudes. We recorded the migrations between northern Europe and sub-Saharan Africa of European nightjars Caprimulgus europaeus to explore their altitudinal space use during spring and autumn flights and to test whether their climbs and descents were performed according to predictions from flight mechanical theory. Spring migration across all regions was associated with more exploratory vertical flights involving major climbs, a higher degree of vertical displacement within flights, and less time spent in level flight, although flight altitude per se was only higher during the Sahara crossing. The nightjars commonly operated at ascent rates below the theoretical maximum, and periods of descent were commonly undertaken by active flight, and rarely by gliding flight, which has been assumed to be a cheaper locomotion mode during descents. The surprisingly frequent shifts in flight altitude further suggest that nightjars can perform vertical displacements at a relatively low cost, which is expected if the birds can allocate potential energy gained during climbs to thrust forward movement during descents. The results should inspire future studies on the potential costs associated with frequent altitude changes and their trade-offs against anticipated flight condition improvements for aerial migrants.

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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Ascent, Climbing costs, Descent, Exploratory movement, Individual-based tracking, Wind
in
Journal of Experimental Biology
volume
224
issue
20
article number
jeb242836
pages
1 - 1
publisher
The Company of Biologists Ltd
external identifiers
  • scopus:85118189873
  • pmid:34647575
ISSN
0022-0949
DOI
10.1242/jeb.242836
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2021 Company of Biologists Ltd. All rights reserved.
id
0203839a-23a9-4b3b-8e77-6b9315ae282e
date added to LUP
2021-11-13 11:29:59
date last changed
2024-06-16 22:55:19
@article{0203839a-23a9-4b3b-8e77-6b9315ae282e,
  abstract     = {{<p>Avian migrants may fly at a range of altitudes, but usually concentrate near strata where a combination of flight conditions is favourable. The aerial environment can have a large impact on the performance of the migrant and is usually highly dynamic, making it beneficial for a bird to regularly check the flight conditions at alternative altitudes. We recorded the migrations between northern Europe and sub-Saharan Africa of European nightjars Caprimulgus europaeus to explore their altitudinal space use during spring and autumn flights and to test whether their climbs and descents were performed according to predictions from flight mechanical theory. Spring migration across all regions was associated with more exploratory vertical flights involving major climbs, a higher degree of vertical displacement within flights, and less time spent in level flight, although flight altitude per se was only higher during the Sahara crossing. The nightjars commonly operated at ascent rates below the theoretical maximum, and periods of descent were commonly undertaken by active flight, and rarely by gliding flight, which has been assumed to be a cheaper locomotion mode during descents. The surprisingly frequent shifts in flight altitude further suggest that nightjars can perform vertical displacements at a relatively low cost, which is expected if the birds can allocate potential energy gained during climbs to thrust forward movement during descents. The results should inspire future studies on the potential costs associated with frequent altitude changes and their trade-offs against anticipated flight condition improvements for aerial migrants.</p>}},
  author       = {{Norevik, Gabriel and Åkesson, Susanne and Andersson, Arne and Bäckman, Johan and Hedenström, Anders}},
  issn         = {{0022-0949}},
  keywords     = {{Ascent; Climbing costs; Descent; Exploratory movement; Individual-based tracking; Wind}},
  language     = {{eng}},
  number       = {{20}},
  pages        = {{1--1}},
  publisher    = {{The Company of Biologists Ltd}},
  series       = {{Journal of Experimental Biology}},
  title        = {{Flight altitude dynamics of migrating European nightjars across regions and seasons}},
  url          = {{http://dx.doi.org/10.1242/jeb.242836}},
  doi          = {{10.1242/jeb.242836}},
  volume       = {{224}},
  year         = {{2021}},
}