Here's another observation experiment for you the next time you are at a beach...
Pelicans (of the "Brown Pelican" variety on the USA OBX) I have observed fly in groups of 2^N (where max N I've witnessed is 5) quite often, as in a statistically significant often. Count pelicans the next time you see some flying by. As 2^N is even, this makes one leg of the V they often fly in longer, too.
