Things have gotten downright Darwinian at the bird feeders lately. Several squadrons of Common Redpoll, which we haven’t seen at the feeder before, have descended upon the feeders and seem to have almost completely displaced our regular visitors, the American Goldfinches. Where there were once as many as 20 goldfinches feeding at one time, we now see around twice as many redpolls. If there are any goldfinches fighting for a feeding spot in that melee, it’s two or three at most. The two finch species do not seem to be taking turns: I haven’t seen the goldfinches wait for the redpolls to finish; it’s either redpolls or nothing. The redpolls appear to be a bit more fearless; they’re certainly more numerous. I imagine the goldfinches will admit defeat and head elsewhere, if they haven’t already done so. The chickadees, starlings, nuthatches and woodpeckers, who arrive in ones and twos and don’t swarm like sky piranhas, seem unaffected.
Finch behaviour at the feeders was interesting even before the redpolls turned up. When startled, which was often, they would fly off at once. Usually all but one bird, who would keep eating at the feeder. I thought to myself when I saw that a few times: here are birds that hedge their bets. Most are choosing to flee, on the basis that your chances of survival improve if you give up opportunities to eat, but spend energy fleeing from danger. But then there’s one bird that chooses to accept a higher risk of being eaten in order to get at more food. This is diversification in the financial sense, applied to natural selection — spreading out risk by, in this case, adopting multiple survival strategies.