[Fisherman]

My hen at the bottom of the pecking order tends to get a bit of a beating when they go up to roost. So last night I decided to watch what was going on (as you do) and stayed longer than I first thought I would. After the usual commotians some of the hens started to fall asleep and I noticed that their eylids close from bottom upwards over their eyes. Is this the same for all birds and why have they evolved this way?

It's a sad life I lead but I like it

[Aunt Sally]

They actually have 3 eyelids.  The third one is called a nictitating membrane which is just  thin transparent skin that the bird can see through while it wipes their eyes.

[Fisherman]

Thank you Aunt Sally. I assume they have a top and bottom eye lid as well as the nictitating (not sure how to prenounce that) membrane, the bottom eye lid being the predominant one? It makes you realise how delicate they are!

You learn something every day.