As I have reported throughout the winter, a flock of lesser goldfinches stayed on our Littleton farm, declining to head for the Desert Southwest as had been their long-established tradition. During those months, which were generally mild and relatively snowless, these beautiful freeloaders had the thistle (niger) feeder to themselves, disturbed only by an occasional, brief visit from one of our abundant house finches.
Today, for the first time, a small flock of American goldfinches arrived to take advantage of the handouts. Larger and bulkier than their lesser cousins (and especially intimidating due to the molting plumage of the males), these new opportunists were initially more aggressive, displacing the lesser goldfinches from the feeder; this pattern continued until the male lessers seemed to have had enough (after all, this had been their exclusive domain for the past several months). Taking charge, they refused to be dislodged and the American goldfinches soon decided to give up the battle, feeding with the lessers in peaceful coexistence.
Such confrontations are common in nature, fueling natural selection through competition and "the survival of the fittest." Sometimes, however, when resources are plentiful, cooperation makes more sense. Humans should take note!