It’s all about sex. This weekend, the bulk of migrating songbirds will finish the long journey to Maine and begin the competition for territories and mates. Actual fights are rare. Rather, it’s mostly a contest of song.
Males stake out an area to call their own and literally sing away the competition. If another male intrudes, there is a brief chase, generally won by the defender, usually without harm to either combatant. Thus, the forest gets divided into individual territories.
However, there can be brief comical moments.
A couple of years ago, I watched a pair of male black-and-white warblers sitting side-by-side on a branch. They had arrived overnight, and neither had established an effective claim on the grove. They stood an inch apart and sang directly into each other’s faces, arguing like a pair of New York cab drivers.
I watched something similar last weekend. Two singing Nashville warblers were on opposite sides of a logging road. I knew from experience that they were too close to each other. Nashville warblers are staunch defenders of their territories and can’t tolerate another singing male within 75 yards. These had probably arrived overnight, and their singing competition had not yet determined the winner. The contest was under way.
You can actually watch the results of these battles. Each species has a different tolerance for rival encroachment. If you place a large number of birdhouses in a grassland, tree swallows and eastern bluebirds can successfully nest side-by-side, while also maintaining sufficient territorial distance from others of their own kind. For species nesting deep in the grass, territory size tends to be much smaller. Bobolinks and savannah sparrows are quite tolerant of nearby competitors.
The territory sizes are even more apparent when many defending males are singing simultaneously. On one of the morning bird walks during last weekend’s birding festival in Stonington, a group of birders stood in one spot, surrounded by black-throated green warblers. This species is abundant in Maine, so it’s normal to hear several singing males at once. Four warblers were singing from different directions, and the distance between each was nicely spaced at about 150 yards.
Mourning warblers are unusual in Maine, but where they breed, they often cluster. In one of my favorite sites west of Baxter State Park, they are precisely spaced 100 yards apart.
It’s particularly fun to observe the contests between ovenbirds. This ground-dwelling warbler is very protective of its territory. Many birds will move in the direction of a perceived intruder, sometimes slowly, sometimes more directly. But the ovenbird moves to investigate an intruder as if shot out of a cannon, bold and angry. Each ovenbird has a precise understanding of its territory and its boundaries.
In Bangor City Forest, there is one particular trail intersection where ovenbirds have territories in each quadrant. The road itself is the dividing line between their territories. All four ovenbirds can be heard singing at once, each from their own side of the crossroad. But if one bird crosses the road and sings, all heck breaks out. The presiding male in that territory immediately challenges the intruder and chases the bird back across the road. If that chase accidentally wanders into an adjacent territory, the third male joins the fray until each bird is back on their own side of the property line.
Field guides show that ovenbirds have small orange patches on top of their heads. However, birders seldom see it unless the bird is angry. They raise the orange crest to show aggression. Ruby-crowned and golden-crowned kinglets also flash their colorful crests only during territorial squabbles.
For red-winged blackbirds, it’s the red shoulder patch that displays dominance. A singing male on its territory flashes the red proudly. But marshes are a funny place. Unlike a forest, where males can disperse and divide up the woods, marshes concentrate birds. In order to forage, blackbirds have to cross each other’s territories routinely. When that happens, the male birds deliberately cover their red shoulders so that they don’t display aggression and invite attack. Since marshes concentrate food and space, territories tend to be much smaller. Marsh wrens, common yellowthroats, rails, swamp sparrows and a host of other birds squeeze into a smaller space.
For the next month, note the distance between singing birds. Observe the circumstances under which they chase each other. Watching birds is fun; watching bird behavior is fascinating. It turns out, they have personalities. Some territory defenders are shy, some are sneaky, and some are downright ornery.
Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. Bob developed the Maine Birding Trail, with information at mainebirdingtrail.com. Bob can be reached at firstname.lastname@example.org.