Plaintive Cuckoo’s nictitating membrane

posted in: Morphology-Develop. | 2

Dr Jonathan WK Cheah managed to capture an image of the Plaintive Cuckoo (Cacomantis merulinus) showing the nictitating membrane moving half-way across the eye just before the bird took off from the ground (above right). Obviously the bird spotted a prey and was about to pounce on it. The images on the left shows the normal eye.

Birds have three eyelids – one upper, one lower and a third, the nictitating membrane. This membrane is between the two other eyelids and the cornea and moves sideways. It is used to clean and protect the eye.

When flying, the bird cannot afford to close its eyelids as this leads to loss of vision. The nictitating membrane protects the eye when the bird lunges into the undergrowth in search of prey. It also functions when the bird is under water going after fish.

An earlier post shows the nictitating membrane of the Buffy Fish Owl (Ketupa ketupu).

Images by Dr Jonathan WK Cheah.


2 Responses

  1. […] to the regular eyelids, cleaning the eye’s surface and keeping it moist.” In an earlier post we showed the nictitating membrane moving sideways in the case of the Plaintive Cuckoo (Cacomantis […]

  2. […] to cover the eye. The nictitating membrane or the third eyelid is a translucent membrane that moves sideways, although in the owl this membrane moves diagonally. The nictitating membrane cleans the eye and […]


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