The nictitating membrane or “third eyelid” that birds have, is something we need to manage as bird photographers. It moves horizontally across the eye episodically or during risky behaviours to protect the eye. When covering the eye the bird has a bit of a dull eyed “zombie” look that is not ideal if trying to portray them at their best.

My camera lives in burst mode so even with perched or stationary birds I take short burst of images when a good pose happens. The logic being that if an image is spoiled by a nicitating membrane, one image before of after in the burst will capture the phase with a nice clear eye.

The Matuku moana/White-faced heron juvenile from last week was a case in point as illustrated by this sequence of images taken as a short burst. I would rather delete some duplicate images than have only a choice of one image with a covered eye.

Photos with Nikon Z9 and Nikkor Z 400mm f4.5 VR S