Anticipatory Manoeuvres in Bird Flight.
It is essential for birds to be agile and aware of their immediate environment, especially when flying through dense foliage. To investigate the type of visual signals and strategies used by birds while negotiating cluttered environments, we presented budgerigars with vertically oriented apertures of different widths. We find that, when flying through narrow apertures, birds execute their maneuvers in an anticipatory fashion, with wing closures, if necessary, occurring well in advance of the aperture. When passing through an aperture that is narrower than the wingspan, the birds close their wings at a specific, constant distance before the aperture, which is independent of aperture width. In these cases, the birds also fly significantly higher, possibly pre-compensating for the drop in altitude. The speed of approach is largely constant, and independent of the width of the aperture. The constancy of the approach speed suggests a simple means by which optic flow can be used to gauge the distance and width of the aperture, and guide wing closure.
Queensland Brain Institute, University of Queensland, St Lucia, QLD 4072, Australia.
Hong D
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Queensland Brain Institute, University of Queensland, St Lucia, QLD 4072, Australia.
Ingo
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Schiffner
Queensland Brain Institute, University of Queensland, St Lucia, QLD 4072, Australia.|School of Information Technology and Electrical Engineering, University of Queensland, St Lucia, QLD 4072, Australia.|ARC Centre of Excellence in Vision Science, University of Queensland, St Lucia, QLD 4072, Australia.
Mandyam V
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Srinivasan
D000818:Animals; D001696:Biomechanical Phenomena; D005426:Flight, Animal / Q000502:physiology*; D046408:Melopsittacus / Q000502:physiology*; D014921:Wings, Animal / Q000502:physiology*