How can you tell if a chicken is in pain?

[Chocobo]

I have gotten help with what appears to be a sick chick (original thread: https://www.backyardchickens.com/forum/viewtopic.php?id=523696) and am hopeful everything will turn out well.
But while looking in on her I had the thought that even though she looked tired she didn't appear to be in any pain. I then realized that I didn't actually know what a chicken in pain would look like except one that was peeping loudly and constantly.
In a general sense, how do chickens actually react to pain?
Do they always just peep or vocalize loudly?
If not, is there any way to tell if a chicken is in pain just by looking at it?

 

[Blue_Myst]

Birds are very reluctant to show pain, unfortunately. It would make things a lot easier if they did. When they do show pain or discomfort, you know something is definitely wrong.

You're right about the chicks, they usually peep loudly and constantly if they feel pain. You may also see them with their eyes closed and huddled up somewhere, or with their beaks open, like they're panting.

 

[Happy Chooks]

Quote:
I agree.