From: Andy Soos, ENN
Published March 18, 2011 01:06 PM

Why Birds Fly into Power Lines and Similar

Birds are different from human beings obviously. Birds have been known to fly into objects and knock themselves out. Why does this happen? A sensory ecology framework is used in a new research study to seek to assess why flying birds collide with prominent structures, such as power lines, fences, communication masts, wind turbines and buildings, which intrude into the open airspace. Such collisions occur under conditions of both high and low visibility. It is argued that a human perspective of the problems posed by these obstacles is unhelpful. Birds live in a different visual world. When in flight, birds may turn their heads in both pitch and yaw to look down, either with the binocular field or with the lateral part of an eye’s visual field. Such behavior may be usual for them and results in certain species being at least temporarily blind in the direction of travel.

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Scientists have previously found that that birds fly into power lines because they have blind spots in their field of vision.  Experts discovered that cranes, bustards and storks were unable to see obstacles straight ahead when they tilted their heads downwards in flight.  The earlier study was published in the journal Biological Conservation in November 2010.

In some other cases the reflections in a window may encourage a bird to attack the window as a rival.

In the new study it was found that even if birds are looking ahead, frontal vision may not be as good as side vision. In general, high resolution occurs in the lateral fields of view and frontal vision in birds may be tuned for the detection of movement rather than the detection of high spatial detail.Birds probably employ lateral vision for the detection of foraging opportunities and predators. The detection of these may be more important than simply looking ahead during flight in the open airspace.

Even if the bird is facing forward, they may fail to see an obstacle; perceptually they have no ability to perceive for human artifacts such as buildings, power wires or wind turbines. Birds have only a restricted range of flight speeds that can be used to adjust their rate of gain of visual information as the sensory challenges of the environment change.

It is argued that to reduce collisions with known hazards, something placed upon the ground may be more important than something placed on the obstacle itself.  However, there is unlikely to be a single effective way to reduce collisions for multiple species at any one site. Warning or diversion and distraction solutions may need to be tailored for particular target species.

For further information:  http://onlinelibrary.wiley.com/doi/10.1111/j.1474-919X.2011.01117.x/abstract;jsessionid=2DE29BA4DDFC4993A5AA9381745282DF.d01t03

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