It’s nesting season for some of the resident birds. Having staked out a territory and driven off the competition, it’s time to find that perfect little home in which to raise the kids this year. For some species, the safest place is a cavity in a tree or nest box, where the offspring will hopefully be safe from predators. The other day while I was down by the pond in the far backyard looking at turtles, a pair of Black-capped Chickadees were flitting in and out of a notch in a dead branch just a few feet away.
This cavity may have been used by a previous owner (e.g., a woodpecker) because the entrance is quite a bit larger than the chickadee is. Nevertheless, this pair is modifying the cavity to suit their needs this year — for example, the typical cavity for a chickadee nest is about 8 inches deep. After excavation, they will add a layer of moss and small sticks, and then another layer of soft fur to line the nest cup. It’s quite a production.
But the number of suitable cavities of just the right size are limited, and there are lots of chickadees, House Wrens, Tree Swallows, and Bluebirds that require one about this size to start building their nest. While I was watching the courtship activities of the osprey pair at the marsh the other day, I saw some of this interspecific competition between chickadees and Tree Swallows, each of whom seemed to be claiming a cavity in a tall, dead snag.
I didn’t stay to see who got control of this cavity. Tree Swallows are a little larger than chickadees and weigh about 50% more, so it’s possible they might have ousted the chickadees and claimed this cavity for their own home. I’ll have to check back later to see who “won”.