In the link that above, one of the posters wondered what kind of research showed that chickens can count or have numerical abilities. There have been quite a few studies that support that birds have numerical abilities. Here is a link to info on a study that shows young chicks know the difference between "less" and "more." There is even a short video.
http://www.guardian.co.uk/science/2009/apr/01/chicks-mathematics-arithmetic-sums
http://www.guardian.co.uk/science/2009/apr/01/chicks-mathematics-arithmetic-sums