wgeoff

Interesting observation.

Several Bittern species have a dark mark at the rear of the iris - Schrencks's and also Cinnamon it appears.
Here is an old Screnck's photo of mine



but it seems Yellow Bittern does not.

I still don't know what the function of this dark iris mark is.

[ Last edited by wgeoff at 7/10/2015 09:34 ]