I was out at the Dry Tortugas the other day, trying to get a picture of a Roseate Tern feeding, when I shot off a few frames of a Brown Pelican diving. I never get tired of seeing Brown Pelicans. They're kind of like the John Goodman of the bird world – big and goofy looking, but amazingly graceful. I think of them as role models.
Anyhow, caught a few frames of the pelican diving, then the splash, and then a few of a Laughing Gull, being an asshole and stealing unearned fish. (You can see the whole sequence below.)
In proper scientific terms it's called kleptoparasitism – one bird stealing food from another as part of a foraging strategy. And it's not a new thing. Laughing Gulls have been ripping off Brown Pelicans like this for tens of thousands of years. Since before our kind ever scratched the first picture of a stag on the wall of a cave.
The mechanics work like this: the pelican flies around until it seas some fish, then plunges head first into the water, opening it's mouth and taking in about 20 pints of water and fish. Kind of like a seine net. Except a seine net doesn't hold water like a pelican's pouch – properly called a gulag sack – does.
So the pelican has to open it's mouth a little to let the water drain out before it can be light enough to fly again. And while it's sitting there with its mouth open, the Laughing Gulls will swoop in, jab their bills into the gap, steal a fish, and take off. If the pelican doesn't open his mouth, the Laughing Gulls will sometimes fly in and stand on his head until he does.
It's kind of a fish tax. An evolved, but not symbiotic, relationship.
It's nature and really, you shouldn't judge. But how can you not take sides? Laughing Gulls are assholes.