Blink of an Eye

July 19, 2013 Posted by: EH - Park Ranger (Yosemite Valley)
Common Raven

Eating lunch at Taft Point (a lovely overlook reached by a trail leaving from Glacier Point Road), my favorite bird paid me a visit. A large, black bird with an inquisitive nature, the common raven (Corvus corax) is a frequent visitor to campgrounds, picnic areas, and picturesque overlooks. While the raven kept an eye on my peanut butter and jelly sandwich, I caught the raven's eye on film.

Like most vertebrates, birds have eyelids that they close while preening or sleeping. But their eyes also have another protective shield, a nictitating membrane! This additional "eyelid" sweeps over the eye sideways, from the corner of the eye closet to the beak across to the outside corner, functioning to keep the eyeball moist and clear of dust. The membrane can also be useful during flying as it is translucent, still allowing the bird to see!

You know the little pink nub in the corner of your eye? It's actually an evolutionary remnant of the nictitating membrane, no longer functioning as it does for birds.

Although dust may get into our eyes, these ravens are set for a patient perch at a blustery overlook, staying on the look out for leftover lunch. So keep your food close, or it may disappear in the blink of an eye! 

Nature Scene, Glacier Point, EH

5 Comments Comments icon

  1. Ken
    December 24, 2014 at 12:06

    We've got a pair a ravens at our Yosemite cabin. They are very territorial, and extremely intelligent. They use different vocalizations to warn of preditors

  2. August 20, 2013 at 06:05

    Designed with built-in goggles! Nice. Anybody else ever outsmarted by a raven? Keep etting your lunch on your lap isn't always close enough to be safe from these cool characters

  3. July 28, 2013 at 12:46

    How do you differentiate between a crow and raven? Look at the tail: round raven; square crow.

  4. July 26, 2013 at 09:23

    Historically, ravens have not been a big player in Yosemite's ecosystem (see Grinnell study). I am concerned with the growing number of ravens in the park. I'm afraid their numbers are artificially high due to consumption of human food. My concern is that they will bump a more endemic species from their ecological niche, as well as preying on nests of birds more commonly associated with Yosemite.

  5. July 24, 2013 at 09:51

    How do you differentiate between a crow and raven? I've been calling these crows over here near the Chowchilla mountains. They seem to be paired up. Also they make a clicking type sound while perching.

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Last updated: July 19, 2013

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