Are Birds Small?
Are birds small? Our intuition tells us birds are smaller than mammals—but wait. We're big mammals. Might we be biased? It turns out that flight is the main thing that determines body size, not what sort of animal you are. I found that flying birds are on average bigger than flying mammals (namely bats). More surprisingly, flightless birds are bigger than flightless mammals. (Remember, most mammals are actually quite small; rodents and the like.) So birds are a little bigger than mammals. This infuriates mammalogists.