I never said the authors didn't discuss this. I was explaining it to people less familiar with this issue.

I realize the results support general face recognition. Pigeons are pretty good at visual discrimination on trained/experienced material.

But results should still be considered somewhat "unnatural" as the research was not on normally developed pigeons.

Interesting story: the university I attended used to have a professor who had pigeon housing on the roof of the psych building and would use wild pigeons for experiments. He fed the birds to coax them to participate.

Very ethical because essentially the birds volunteered. And high quality results because they were average wild pigeons in experience and ability.

However the university shut it all down.

This was before my time there but that's the story I was told.