YELLOWSTONE NATIONAL PARK — No, that bird isn’t asleep.
Yellowstone National Park (YNP) shared photos this week of a red-tailed hawk perched on a weathered snag in the park, blinking its nictitating membrane, which the park defines as the “the translucent shield that protects its eyes from dust, debris, and injury while still allowing it to see.”
“This built-in ‘goggles mode’ keeps the hawk’s vision sharp as it hunts and scans the landscape,” YNP posted to social media.
Approximately 150 bird species nest in the park, including about a dozen raptor species, per YNP. Birds aren’t the only animals who possess this special membrane. Mammals including dogs and cats also possess the adaptation, along with certain reptiles, fish and amphibians.
“Birds lead lives that could be very hard on the eyes: like flying at breakneck speed, racing for cover into a dense thicket, or diving under water to capture a spiny, struggling fish,” the National Audubon Society shared on its podcast. “Fortunately, birds have evolved a structure for protecting their eyes. Like humans, they have upper and lower outer eyelids. But beneath the outer eyelids lies an extra eyelid, called the nictitating membrane. … This extra eyelid is hinged at the inner side of the eye and sweeps horizontally across the cornea. The nictitating membrane is largely transparent, and it helps keep the eye moist and clean.”
Learn more about the birds of Yellowstone here.
