Two game wardens, seven hunters, and a cow

In another bit of Illinois stupidity, three hunters yesterday killed a trupeter swan by mistake:

U.S. Fish and Wildlife Service officials say hunters thought they were shooting at a snow goose but actually killed a rare trumpeter swan at a conservation area in far southern Illinois.

One of the comments on the above-linked page gets it right: "[S]houldn't a hunter be able to identify what [he is] shooting?" Yes. Let's compare: Snow goose:

Trupeter swan:

Hey, I'm not an orinthologist or anything, but those birds look different to me.