Scientists find bird-centric solution to avian collisions
Ever been startled by a sudden thud on the window, only to see some poor bird fly away half-dazed? A study published in Ibis, the International Journal of Avian Science, sheds new light on why some species of bird are prone to colliding with large man-made objects, many of which seem easily avoidable to human eyes. The researchers believe their results could be vital in helping to save certain species whose very survival is threatened by their inability to avoid collisions. 'From a human perspective it appears very odd that birds so often collide with large objects as if they don't see them,' commented Professor Graham Martin from Birmingham University in the UK. He said that it is widely held that flight in birds is controlled primarily by vision, an idea captured by the phrase 'a bird is a wing guided by an eye,' but he pointed out that 'birds live in a different visual world to humans'. To get a better understanding of how birds view the world Professor Martin turned to sensory ecology, a field of study which investigates how sensory information underlies an animal's behaviour and its interactions with the environment. 'Previously most proposed solutions to bird collisions only consider a human perspective of the problem,' said Professor Martin. 'Put simply, it has been a matter of finding a solution to bird collision problems based upon making the perceived hazard more conspicuous to human observers, not birds.' His research revealed that a subtle set of interrelationships exists between a bird's visual capacities, the interpretation of sensory information, and the behaviour of birds when flying in open airspace. 'When in flight, birds may turn their heads to look down, either with the binocular field or with the lateral part of an eye's visual field,' explained Professor Martin. 'Such behaviour results in certain species being at least temporarily blind in the direction of travel.' Professor Martin also explored how avian frontal vision is tuned for the detection of movement, rather than spatial detail. When a bird is hunting detecting movement may be more important than simply looking ahead into open airspace. In addition, birds have a restricted range of flight speeds; for many birds it is simply impossible for them to fly slowly, making it difficult to adjust the rate of information they gain if visibility is reduced by rain, mist or low level lights. The problem of bird collisions is a serious concern for conservationists. Research suggests that bird mortality caused by collisions with human artefacts - from office block windows to power lines and wind turbines - is the largest unintended human cause of avian fatalities worldwide. Indeed, collisions with large and prominent obstacles may even threaten the survival of endangered species. In Europe, scientists estimated that over a 16-year period approximately 25 per cent of juvenile and 6 per cent of adult White Storks (Ciconia ciconia) died annually from power line collisions and electrocutions. 'Armed with this understanding of bird perception we can better consider solutions to the problem of collisions,' insisted Professor Martin. He agreed that 'while solutions may have to be considered on a species by species basis, where collision incidents are high it may be more effective to divert or distract birds from their flight path rather than attempt to make the hazard more conspicuous.' He concluded that while 'the human viewpoint provides just one way of appreciating and understanding the world...such is the difference between human and birds' eye views that a human perspective on the problem of bird collisions is quite misleading.'For more information, please visit: Ibis - the International Journal of Avian Science: http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1474-919X University of Birmingham Centre for Ornithology http://www.ornithology.bham.ac.uk/index.shtml
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