Why birds fly into power lines
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 behaviour may be usual for them and results in
certain species being at least temporarily blind in the direction of
travel.
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. In some
other cases the reflections in a window may encourage a bird to attack
the window as a rival.
In a 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 artefacts 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.
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