Basic logic would seem to imply that in terms of pecking order at bird feeders, smaller birds would be displaced by larger ones. To a large extent this is in fact true – except in the case of Pine Siskins, Carduelis pinus.
Perhaps the siskins that have recent reappeared at our feeders are simply more belligerent than normal. Maybe they are simply juveniles – young thugs that stand around near feeders like disaffected teen-agers in a shopping mall, just looking for someone to bother. Whatever the case, the fact that these quarrelsome little birds have been recently observed giving the bum’s rush to other larger birds, particularly the local Purple Finches, Carpodacus purpureus, has me contemplating these interspecies interactions.
When the siskins run the Purple Finches off the feeders, they aren’t simply satisfied that the finches take a place on a nearby branch and, assumably, await the departure of the aggressors. After only a moment of so, the siskins will leave the feeder and proceed to harass the finches on the off feeder perches as well, being not content until the larger bird is completely out of the immediate area.
Of course, the arrival of a truly larger bird, such as a grosbeak or even a jay will displace the siskins. However they will then only leave after a considerable and noisy interchange, and even then still calling back – possibly obscenities – at the displacing bird. While the arrival of the jay can be understood to elicit both alarm and avoidance, what with jays being possible nest predators and all, the aggression toward the finches is mysterious.
I know of no documentation of Purple Finches posing any threat, other than the ubiquitous one of competitors for the same food sources, to Pine Siskins. Yet perhaps this in itself is enough. The siskins, being among the smaller of the bird species found in the area, are likely in danger of being left the scraps of whatever food is available, thus they have become rather scrappy themselves in their daily acquisition of, as the economists say, necessary resources. This is certainly a question worth continued contemplation.
Peace and good bird watching.
