If you think humans have a hard time getting along, you should look at your backyard birds. Some of them are getting pretty testy with each other.
For much of the year, birds are tolerant of their own kind. During nesting season, all bets are off.
It varies by species. Some birds accept their neighbors better than others. Much of the belligerent behavior is determined by a bird’s self-preservation strategy. Take pigeons, for example. They’re big, slow and tasty. Their survival chances improve if they stick together, with multiple birds watching out for trouble.
Blue jays also know that they are a prime target for predators, due to their size, lack of speed and a near total inability to hide. They may push each other around at the bird feeder, but they still get comfort from having friends nearby to sound a warning.
Some birds that reside in challenging habitats are slower to anger. Birds in grasslands, such as bobolinks, hide from predators in the weeds. But in so doing, they hide from each other as well. It’s hard to prevent a mate from wandering, and fidelity is not an oft-practiced virtue among hayfield species.
Marsh birds face the same challenge, though each species deals with the challenge in its own way. Swamp sparrows sing. A lot. Mostly, it’s a vocal duel, but if one encroaches too closely on the other, a fight can break out. Rails are at even greater risk of blindly bumping into each other among the reeds, whereupon a battle results. They vocalize often enough to remind neighbors of their jealously guarded territories.
Colonial birds tolerate each other out of necessity. Barn, cliff and bank swallows have limited choices of nesting sites, and typically cram together in them. Fights are uncommon, but so is mate fidelity.
On the other hand, treetop birds are quick to anger if they spy an intruder. I’m not sure why, but I’ve seen more fights between black-throated green warblers over the last week than in previous years. Usually, they work out their boundary disputes before Memorial Day. Bad weather through mid-May seems to have delayed and prolonged their arguments.
Black-and-white warblers are easily enraged by rivals. They typically get back to Maine earlier than black-throated green warblers, but even their disputes seemed to have lasted longer this season.
Ovenbirds put up with nothing. They have a precise understanding of where their territories end and their neighbor’s begins. Any trespass results in an immediate fight. Since ovenbirds are so loud, you can sometimes tell the size of a bird’s territory just by how far it is from the next singing ovenbird. Split the distance, and there’s the boundary.
Inevitably, the more birds there are, the smaller their territories will be. On many bogs in Maine, palm warblers protect huge territories. But in places like Orono Bog, so many nest along the bog boardwalk that their territories are considerably smaller. You can tell the size of their defended territories by how close they are to other singing birds.
Red-eyed vireos are champion singers. I’d wager that they sing more songs in more places than any other species in Maine. There are so many vireos that they have no choice but to tolerate nearby rivals. I walked my road earlier this week and found five red-eyed vireos all singing within a three-acre patch of woods. Few other birds would tolerate so many rivals so close.
Philadelphia vireos take advantage of this. They are slightly smaller than red-eyed vireos and would typically lose a fight. Therefore, Philadelphia vireos evolved to sing a song virtually identical to red-eyed vireos. I can’t tell the difference. Neither can the red-eyed vireo. The Philly arrives earlier and holds territory by posing as a red-eyed vireo — and outsinging his larger rivals. Phillies even sing while sitting on the nest, keeping up the ruse as long as necessary.
Birds that normally flock together are now settling into nesting territories. Finches and waxwings form big flocks for much of the year, but right now you may see them only in pairs.
That’s my invitation to you this week.
Spy on the birds to see how they behave around each other. Which birds are content to stay in groups? Which ones argue? Listen for two singing birds of the same species and estimate how far apart they are. Is it the same distance as other singing birds? It costs 20 bucks to watch a movie or Netflix.
Watching nature is free.
