近观乌鸦，翻白眼，跟谁过不去？
Close up: Watch This Crow Use its Translucent "Third Eyelid"
见过乌鸦翻白眼吗？见过乌鸦黑羽毛下面的羽毛是什么颜色的吗？
下面的英文是gemini写的，再下面的中文是deepseek翻译的。
看看视频，看完后你觉得它在跟谁过不去？
看完后你还觉得天下乌鸦一般黑吗？
Caught this lone crow in a tree the day before yesterday displaying its nictitating membrane. This "third eyelid" is a translucent layer that protects and moistens the eye while allowing the bird to maintain some level of vision. Even though you only see one crow here, there were actually four others nearby in the same tree.
What is that translucent eyelid?
The white or cloudy film you see moving cross the eye is the nictitating membrane, often called the "third eyelid". Unlike human eyelids, which move up and down, this membrane moves horizontally across the eye (from the inner corner outward).
Why do crow have it?
Protections: it acts like a pair of safety goggles, protecting the eye from dust, wind, and debris while the bird is flying or foraging.
Moisture: it sweeps across the eye to keep the cornea moist and clean without completely blocking the bird's vision.
Maintaining Sight: Because it is translucent, the crow can still see well enough to detect motion or threats even while the membrane is closed. This is vital for a bird sitting in a tree with four other companions, as it stays alert to the group's surroundings.
(Thank gemini for writing the above words).
前天在树上拍到这只独自停留的乌鸦，它正在展示自己的瞬膜。这层“第三眼睑”是半透明的薄膜，能在保护眼睛、保持湿润的同时让鸟类维持一定视野。虽然画面里只有一只乌鸦，其实当时同一棵树上还有另外四只同伴。
那层半透明眼睑是什么？
你看到横向划过眼球的白色/灰白色薄膜就是瞬膜，常被称为“第三眼睑”。它与人类上下闭合的眼睑不同，是水平方向（从内眼角向外侧）扫过眼球的。
乌鸦为何需要瞬膜？
保护作用：如同护目镜，在飞行或觅食时保护眼睛免受灰尘、风沙和碎屑侵扰。
保持湿润：横向扫动能为角膜保湿清洁，且不会完全遮蔽乌鸦的视线。
维持视觉：得益于半透明特性，即使瞬膜闭合时乌鸦仍能清晰感知动作或威胁。这对于与四只同伴共栖树梢的鸟类至关重要——它得以持续警觉群体周边的动静。
（上述文字鸣谢Gemini撰写，鸣谢deepseek翻译成中文）
Camera: Nikon P1000
Watch from 0:00 to 00:19, the translucent membrane （0秒 到19秒，看瞬膜）
Watch at 00:19, the color of the inner feather is white, instead of black（第19秒看黑毛里面是白毛，谁说天下乌鸦一般黑？）
跟谁翻白眼？
谁说天下乌鸦一般黑？
https://www.youtube.com/watch?v=59_nVL7dwxo
