Willet’s Blink

Willet (Tringa semipalmata)

Given the interest in the eye blink of the Great Blue Heron and the Snowy Egret, I thought it would be worth a peek at how the Willet does it. This bird resting on the east shore of the designated Burrowing Owl Sanctuary volunteered for the study, tucking its beak between its flight feathers and keeping one eye open, as is its habit while napping. It turns out that the Willet, or at least this Willet, blinks frequently and conventionally by human standards, that is, with eyelids. In this 15-second video clip, I counted seven blinks. The bird did not use its nictitating membrane, if it has one, as the heron and the egret do. The upper eyelid seemed to do most of the traveling but the lower eyelid also rose to meet it.

This comparison between the Willet and the heron/egret is a bit of apples and oranges. The Willet is napping, while the other two were hunting, specifically, stalking, in a situation where any motion on part of the hunter might alert the prey. It remains to be seen what the Willet does to keep its eyeballs lubricated when it also is in hunting mode. Stay tuned.

Willet (Tringa semipalmata)

Oh, and if you believed that this concern with birds’ blinking is a bit over the top, you should read the December 19 New York Times report on a scientist’s study of blinking in Great-tailed Grackles. The researcher, Dr. Jessica Yorzinski, reflected that during the moments when humans blink, we are temporarily blinded. She wondered how birds in flight managed these interruptions in their vision, which might expose them to danger. She outfitted a group of Great-tailed Grackles with headsets containing a pair of small video cameras, one on each side, focused on the bird’s eye, with a battery-powered radio transmitter on the bird’s back. Like this:

Great-tailed Grackle with blink camera headset. Photo Jessica Yorzinski, Biology Letters 2020/New York Times

Then she chased the birds inside a giant cage to make them fly, and recorded the resulting video.

These birds, she found, blink laterally with their nictitating membranes. The birds blinked more rapidly in flight than when perched at rest, and they blinked almost never during their approach to a landing spot. But at the instant they touched the ground, they blinked most often, possibly to clear their eyes of dust that they stirred up in the landing maneuver. The study appeared in Biology Letters.

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