There are some birds that seem almost too improbable to be real. The American white pelican (Pelecanus erythrorhynchos) is one of them. With a wingspan stretching nearly 9 feet and a bill so absurdly oversized, this is a bird that is hard to confuse with anything else. Yet, despite their enormous size, white pelicans fly with astonishing grace. Flocks can often be seen circling overhead, riding invisible columns of rising warm air called thermal…