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Optic flow cues help explain altitude control over sea in freely flying gulls

  • Julien R. Serres
  • Thomas J. Evans
  • Susanne Åkesson
  • Olivier Duriez
  • Judy Shamoun-Baranes
  • Franck Ruffier
  • Anders Hedenström
Publishing year: 2019
Language: English
Publication/Series: Journal of the Royal Society, Interface
Volume: 16
Issue: 159
Document type: Journal article
Publisher: The Royal Society of Canada

Abstract english

For studies of how birds control their altitude, seabirds are of particular interest because they forage offshore where the visual environment can be simply modelled by a flat world textured by waves then generating only ventral visual cues. This study suggests that optic flow, i.e. the rate at which the sea moves across the eye's retina, can explain gulls' altitude control over seas. In particular, a new flight model that includes both energy and optical invariants helps explain the gulls' trajectories during offshore takeoff and cruising flight. A linear mixed model applied to 352 flights from 16 individual lesser black backed gulls (Larus fuscus) revealed a statistically significant optic flow set-point of ca 25° s-1. Thereafter, an optic flow-based flight model was applied to 18 offshore takeoff flights from nine individual gulls. By introducing an upper limit in climb rate on the elevation dynamics, coupled with an optic flow set-point, the predicted altitude gives an optimized fit factor value of 63% on average (30-83% in range) with respect to the GPS data. We conclude that the optic flow regulation principle helps gulls to adjust their altitude over sea without having to directly measure their current altitude.


  • Evolutionary Biology
  • energy invariant
  • flight modelling
  • motion vision
  • optical invariant
  • visual neuroscience


  • ISSN: 1742-5662
Susanne Åkesson
E-mail: susanne [dot] akesson [at] biol [dot] lu [dot] se


Evolutionary ecology

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+46 70 245 04 23


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Research group


Doctoral students and postdocs

PhD students, main supervisor

Himma Bakam

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