Last month, we posted a story about how falcon cams mounted on the heads of birds reveal some pretty amazing things about the way they hunted their prey.
Well, it sparked our curiousity. So we looked into it some more and interviewed the author. We wondered: will it ever be possible to stop birds from running into objects like wind turbines and power lines? The answer surprised us.
Sometimes the most technologically astute answers are the simplest ones. To keep birds from running into wind turbines? Shut them down or another suggestion we learned about was building sanctuaries near the turbines so birds would divert themselves there instead of wind blades.
Here’s our story published in Txchnologist:
Falcons are particularly astute hunters, able to use a wide visual field to track and attack targets. Their pursuit strategy has evolved so they can hunt fast and erratically moving prey in complex environments.
The wide-angle vision system that makes them such good predators, however, also make them particularly prone to collisions with buildings, wind turbines and power lines.
Now a new understanding of how falcons track and capture their prey may open up future possibilities in designing structures that are more visible to large birds.
Understanding the hunter’s way
For the first time, Haverford College researchers have been able to study how falcons hone in on the positions of their prey during pursuits. And it’s all been captured with miniature video cameras mounted on the predators’ backs or heads.
Our best vision is straight ahead. We’re forwardly oriented and it’s obvious visually that birds tend to have their visuals oriented to the side,” says physicist Suzanne Amador Kane, the lead author of a report published in the Journal of Evolutionary Biology. “We see what’s happening. But falcons are seeing somehow where their prey is going to be and target their prey at an angle in their field of vision that allows them to fly towards where they can intersect.”
At the heart of the falcon’s hunting mastery is a visual system that keeps the image of the targeted prey locked in the same place on the bird’s retina during pursuit and capture.
While data from animal-borne video has been used to study the aerodynamics of avian flight, navigation and flocking energetics, the team’s research represents the first time scientists have used videos to interpret computer simulations of pursuit.
Amador Kane says the falcon’s prey, meanwhile, doesn’t see its attacker until the predator suddenly looms large, a technique known as “motion camouflage.”
It’s that blur in motion that may explain why birds collide with objects like windmills or are prone to fly into reflective buildings. An upcoming Dutch study found high-contrast hanging wire markers decrease bird collisions at power lines.
A new point of view
Graham Martin, an expert on bird collisions at the University of Birmingham, says being able to see from the falcon’s perspective would make a big difference.
Until now, people have tried to solve the problem by looking at it from a human point of view.
Almost half-a-million birds are killed each year when they collide with wind turbines in the U.S. alone, according to the U.S. Fish and Wildlife Service.
“There’s been a little bit of experimentation—markings on the blades to make them more conspicuous—but it’s limited and people are now thinking more carefully about the site and trying not to put them in the path of migrating birds,” Martin says.
For power lines, Martin says there has also been limited success in using flag-like markers with alternating black-and-white stripes to reduce collisions. But such add-on features wear out quickly and can become costly to replace.
In Portugal, one of the most effective ways of cutting down bird collisions with wind turbines has been a very simple one. The turbines are shut down when radars and lookouts detect birds in the vicinity.
While powering down turbines may seem inefficient, Martin says it’s been noted the impact is minimal because the birds are already choosing to migrate during periods of low wind.
Bird fatalities with manmade structures are an unnecessary mortality,” says Martin. “Humans produced the problem and there’s no reason why we shouldn’t figure out a way to fix it either through technological fixes or rethinking.”
Being able to study how falcons see their prey may save them from hitting structures, Martin says.
We’re battling against what we know about the vision of birds. If you put something big in the sky where birds don’t expect something above the tree line, they’ll fly into them and when you string those structures out, you cause major problems,” he says. “They’re not programmed or evolved to believe there’s anything there. So we have to see the world the way they see it.”
Photo credit: Flickr