Battle for the Box: Tree Swallows Vs. Eastern Bluebirds

Every spring a battle is waged between Tree Swallows and Eastern Bluebirds to see who will win occupancy to the nest boxes on my property. Technically, these boxes are designed for Bluebirds, but that doesn’t keep the Tree Swallows from moving in. (Photo of female Tree Swallow courtesy of Ken Thomas.)

I have four boxes staked along a strip of pasture above my home. A couple hundred feet separate these boxes that face a grove of wild cherry trees about fifty feet away. Somewhere I once read that it’s important to position nest boxes close enough to trees so that fledglings might reach the safety of their branches on first flight. Too, nest boxes should never face west since most storm systems roll in from the west. Thus my boxes face east.

But back to the bird battle . . .

Every spring, I watch to see which bird will prevail, the Eastern Bluebird or the Tree Swallow. Visiting the pasture, one day I’ll see a Tree Swallow perched atop a given box but on my next visit will find sitting there a Bluebird. And so these two species chase each other from a nesting box until one finally prevails.

I can’t say why one species will prevail over the other when claiming a particular box, but I do know something else to be true. If you provide several boxes, Tree Swallows and Bluebirds will share the neighborhood, alternating their residency. For instance, if you stake four boxes across a span of pasture, boxes one and three will house Bluebirds while two and four will be home to the Tree Swallows.

Why this is so, I can’t say. But it seems like a reasonable arrangement to me.

So until next time, happy birding!

Georgia Anne