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Loop migration in adult marsh harriers Circus aeruginosus, as revealed by satellite telemetry

Klaassen, Raymond LU ; Strandberg, Roine LU ; Hake, Mikael ; Olofsson, Patrik ; Tottrup, Anders P. and Alerstam, Thomas LU (2010) In Journal of Avian Biology 41(2). p.200-207
Abstract
Loop migration among birds is characterized by the spring route lying consistently west or east of the autumn route. The existence of loops has been explained by general wind conditions or seasonal differences in habitat distribution. Loop migration has predominantly been studied at the population level, for example by analysing ring recoveries. Here we study loop migration of individual marsh harriers Circus aeruginosus tracked by satellite telemetry. We show that despite a generally narrow migration corridor the harriers travelled in a distinct clockwise loop through Africa and southern Europe, following more westerly routes in spring than in autumn. We used the Normalized Difference Vegetation Index (NDVI) to identify potential feeding... (More)
Loop migration among birds is characterized by the spring route lying consistently west or east of the autumn route. The existence of loops has been explained by general wind conditions or seasonal differences in habitat distribution. Loop migration has predominantly been studied at the population level, for example by analysing ring recoveries. Here we study loop migration of individual marsh harriers Circus aeruginosus tracked by satellite telemetry. We show that despite a generally narrow migration corridor the harriers travelled in a distinct clockwise loop through Africa and southern Europe, following more westerly routes in spring than in autumn. We used the Normalized Difference Vegetation Index (NDVI) to identify potential feeding habitat in Africa. Suitable habitat seemed always more abundant along the western route, both in spring and autumn, and no important stopover site was found along the eastern route. Observed routes did thus not coincide with seasonal variation in habitat availability. However, favourable habitat might be more important during spring migration, when the crossing of the Sahara seems more challenging, and thus habitat availability might play an indirect role in the harriers' route choice. Grid-based wind data were used to reconstruct general wind patterns, and in qualitative agreement with the observed loop marsh harriers predominantly encountered westerly winds in Europe and easterly winds in Africa, both in autumn and in spring. By correlating tail- and crosswinds with forward and perpendicular movement rates, respectively, we show that marsh harriers are partially drifted by wind. Thus, we tentatively conclude that wind rather than habitat seems to have an overriding effect on the shape of the migration routes of marsh harriers. General wind conditions seem to play an important role also in the evolution of narrow migratory loops as demonstrated for individual marsh harriers. (Less)
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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Avian Biology
volume
41
issue
2
pages
200 - 207
publisher
Wiley-Blackwell
external identifiers
  • wos:000276934600011
  • scopus:77953337159
ISSN
0908-8857
DOI
10.1111/j.1600-048X.2010.05058.x
language
English
LU publication?
yes
id
c1d7ea9e-0b3b-45b8-b866-d0a9840da160 (old id 1601655)
date added to LUP
2016-04-01 10:59:27
date last changed
2022-07-21 22:29:25
@article{c1d7ea9e-0b3b-45b8-b866-d0a9840da160,
  abstract     = {{Loop migration among birds is characterized by the spring route lying consistently west or east of the autumn route. The existence of loops has been explained by general wind conditions or seasonal differences in habitat distribution. Loop migration has predominantly been studied at the population level, for example by analysing ring recoveries. Here we study loop migration of individual marsh harriers Circus aeruginosus tracked by satellite telemetry. We show that despite a generally narrow migration corridor the harriers travelled in a distinct clockwise loop through Africa and southern Europe, following more westerly routes in spring than in autumn. We used the Normalized Difference Vegetation Index (NDVI) to identify potential feeding habitat in Africa. Suitable habitat seemed always more abundant along the western route, both in spring and autumn, and no important stopover site was found along the eastern route. Observed routes did thus not coincide with seasonal variation in habitat availability. However, favourable habitat might be more important during spring migration, when the crossing of the Sahara seems more challenging, and thus habitat availability might play an indirect role in the harriers' route choice. Grid-based wind data were used to reconstruct general wind patterns, and in qualitative agreement with the observed loop marsh harriers predominantly encountered westerly winds in Europe and easterly winds in Africa, both in autumn and in spring. By correlating tail- and crosswinds with forward and perpendicular movement rates, respectively, we show that marsh harriers are partially drifted by wind. Thus, we tentatively conclude that wind rather than habitat seems to have an overriding effect on the shape of the migration routes of marsh harriers. General wind conditions seem to play an important role also in the evolution of narrow migratory loops as demonstrated for individual marsh harriers.}},
  author       = {{Klaassen, Raymond and Strandberg, Roine and Hake, Mikael and Olofsson, Patrik and Tottrup, Anders P. and Alerstam, Thomas}},
  issn         = {{0908-8857}},
  language     = {{eng}},
  number       = {{2}},
  pages        = {{200--207}},
  publisher    = {{Wiley-Blackwell}},
  series       = {{Journal of Avian Biology}},
  title        = {{Loop migration in adult marsh harriers Circus aeruginosus, as revealed by satellite telemetry}},
  url          = {{http://dx.doi.org/10.1111/j.1600-048X.2010.05058.x}},
  doi          = {{10.1111/j.1600-048X.2010.05058.x}},
  volume       = {{41}},
  year         = {{2010}},
}