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Negotiating an ecological barrier : Crossing the Sahara in relation to winds by common swifts

Author:
  • Susanne Åkesson
  • Giuseppe Bianco
  • Anders Hedenström
Publishing year: 2016-09-26
Language: English
Publication/Series: Royal Society of London. Philosophical Transactions B. Biological Sciences
Volume: 371
Issue: 1704
Document type: Journal article
Publisher: Royal Society

Abstract english

The Sahara Desert is one of the largest land-based barriers on the Earth, crossed twice each year by billions of birds on migration. Here we investigate how common swifts migrating between breeding sites in Sweden and wintering areas in sub-Saharan Africa perform the desert crossing with respect to route choice, winds, timing and speed of migration by analysing 72 geolocator tracks recording migration. The swifts crosswestern Sahara on a broad front in autumn, while in spring they seem to use three alternative routes across the Sahara, awestern, a central and an eastern route across the Arabian Peninsula, with most birds using the western route. The swifts show slower migration and travel speeds, and make longer detours with more stops in autumn compared with spring. In spring, the stopover period in West Africa coincided with mostly favourable winds, but birds remained in the area, suggesting fuelling. The western route provided more tailwind assistance compared with the central route for our tracked swifts in spring, but not in autumn. The ultimate explanation for the evolution of a preferred western route is presumably a combination of matching rich foraging conditions (swarming insects) and favourable winds enabling fast spring migration.

Keywords

  • Biological Sciences
  • Barrier crossing
  • Common swift
  • Migration
  • Migration routes
  • The sahara
  • Wind assistance

Other

Published
  • ISSN: 0962-8436
Susanne Åkesson
E-mail: susanne [dot] akesson [at] biol [dot] lu [dot] se

Professor

Evolutionary ecology

+46 46 222 37 05

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