When Jessica Yorzinski watched long-tail scratches on a field, it wasn’t a contest to see who blinked first. But he wanted the birds to blink.
Dr. Yorzinski dressed the grills, which look a bit like crows, but belong to another family of birds, with head-mounted cameras facing forward. Like other birds, the squeak blinked sideways, throwing a semi-transparent membrane over his eyes. Records have shown that birds spend less time blinking in the riskiest parts of a flight. The finding was published in Biology Letters on Wednesday.
Dr. Yorzinski, a sensory ecologist at Texas A&M University, wondered how animals balance their need to blink with their need to get visual information about their environment.
People, she said, “blink quite often, but when we do that we lose access to the world around us. It made me think about what might happen to other species. “
He worked with a company that builds eye tracking equipment to make a custom bird-sized helmet. Because a bird’s eyes are on the sides of its head, the device is reminiscent of a video camera pointing to the left and one to the right, making the bird look like a sports fan in a beer helmet. The headset was connected to a backpack that held a battery and a transmitter.
Dr. Yorzinski captured 10 large-tailed wild scratches common in Texas to wear this training. She used only male birds, which are large enough to carry the equipment smoothly. Each bird wore a camera helmet and backpack, while Dr. Yorzinski encouraged her to fly over an outdoor enclosure.
She then split the flight videos into stages, from standing and taking off to landing. She said she saw “clear patterns.” As the birds fled, their blinking was faster than when they were on the ground. And just before landing, they were barely blinking.
“Maximizing the visual input I receive in these critical stages of flight and landing makes a lot of sense,” she said. During the fast flight, the collision with another object could be disastrous. Choosing a landing site is also risky. Think of a bird throwing itself on a branch, Dr. Yorzinski said, “If it had gone a little, it might land on nothing and fall to the ground.”
He also saw that the birds blinked most often when they hit the ground. This may have been due to the fact that they had to blink after keeping their eyes open or to protect their eyes from debris. Dr. Yorzinski intends to do other experiments with birds navigating in different environments, such as a forest with many obstacles.
Graham Martin, professor emeritus of avian sensory science at the University of Birmingham in England, said the study was “an interesting work”. But he pointed out that the flights observed by Dr. Yorzinski lasted only a few seconds. He doesn’t think there’s enough evidence to say anything about how birds change their flashes in flight.
“I think we need to see signs of intermittent behavior during longer flights and in other species before any general conclusions are possible,” he said.
Although he has so far studied the question in a single species of bird, Dr. Yorzinski’s findings are similar to those of human pilots. A small 1996 study showed that simulator pilots blinked faster and less frequently while flying, especially during landing. A 2002 study showed that pilots blinked less during the visually demanding parts of a flight.
Human pilots are not exactly like birds, but Dr. Yorzinski said the parallels are interesting. During risky maneuvers, squeaking may benefit from being left with your eyes open. “I think it’s quite remarkable that they’re able to adjust their blinking to this fine scale at times when it’s so important for them to be aware of the environment,” she said.