Chicken open and closes mouth

[Bchicken]

Today is the first time she's doing this, and I have no idea why. There isn't slime in or around her mouth, so it isn't a cold.

Could anyone help? She's about 4 years old.

 

[target022]

I see this on really hot days. It's almost like they are panting.

 

[devora]

It's almost like they are panting.

It's exactly like they are panting.