近觀烏鴉，翻白眼，跟誰過不去？
Close up: Watch This Crow Use its Translucent "Third Eyelid"
見過烏鴉翻白眼嗎？見過烏鴉黑羽毛下麵的羽毛是什麽顏色的嗎？
下麵的英文是gemini寫的，再下麵的中文是deepseek翻譯的。
看看視頻，看完後你覺得它在跟誰過不去？
看完後你還覺得天下烏鴉一般黑嗎？
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).
前天在樹上拍到這隻獨自停留的烏鴉，它正在展示自己的瞬膜。這層“第三眼瞼”是半透明的薄膜，能在保護眼睛、保持濕潤的同時讓鳥類維持一定視野。雖然畫麵裏隻有一隻烏鴉，其實當時同一棵樹上還有另外四隻同伴。
那層半透明眼瞼是什麽？
你看到橫向劃過眼球的白色/灰白色薄膜就是瞬膜，常被稱為“第三眼瞼”。它與人類上下閉合的眼瞼不同，是水平方向（從內眼角向外側）掃過眼球的。
烏鴉為何需要瞬膜？
保護作用：如同護目鏡，在飛行或覓食時保護眼睛免受灰塵、風沙和碎屑侵擾。
保持濕潤：橫向掃動能為角膜保濕清潔，且不會完全遮蔽烏鴉的視線。
維持視覺：得益於半透明特性，即使瞬膜閉合時烏鴉仍能清晰感知動作或威脅。這對於與四隻同伴共棲樹梢的鳥類至關重要——它得以持續警覺群體周邊的動靜。
（上述文字鳴謝Gemini撰寫，鳴謝deepseek翻譯成中文）
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秒看黑毛裏麵是白毛，誰說天下烏鴉一般黑？）
跟誰翻白眼？
誰說天下烏鴉一般黑？
https://www.youtube.com/watch?v=59_nVL7dwxo
