Magnolia Gardens 4-16-2021
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GBH with nictitating eyelid showing.
The nictitating membrane is a third eyelid under the typical two eye lids we all have. It’s a translucent eyelid that can be closed while the other eyelids are open to clean and protect the eye. If you have a cat you might have seen an example of this, as cats also have nictitating membranes.
Each time a pigeon puts its head down to peck at something on the ground, the nictitating membrane moves across the eye to protect it from spiky leaves and grasses. In raptors the membrane covers the eye immediately before the bird slams into its prey, and in exactly the same way the membrane covers the eye just before a plunging gannet hits the water.
In analyzing my images of birds I’ve seen how the nictitating membrane will cover a woodpeckers eyes just before it begins pecking at a tree or stem. I’ve seen instances of the membrane closing just before a bird ruffles its feathers, shaking itself in the process of preening. And in most cases my camera’s shutter just happened to close at exactly the right time to catch the membrane closing or opening while the bird was standing still.
Information from Tim Birkhead and Todd Henson on the internet.
