Field Notes––

Tree Swallows Win The Battle For The Bluebird Box

By Dottie Evans

Early June is a heady time in the yard and garden. One hardly knows where to look first, and there are never enough hours to take in all that beauty.

The showy iris is quite fabulous, the poppies have popped their bright orange petals, and the purple clematis flowers demand second and third looks. Attention must be paid to peonies now coming into their own.

Impossible even to run an errand without being distracted by the glimpse of wild phlox in lavender and white (aka dames’ rocket) gracing an unmowed roadside or a sunny clearing.

Stuck in traffic? Look out the window and enjoy the passing blizzard of cottonwood fluff blowing in the wind like snowflakes with seeds attached. If all of them took root and survived our long, cold winters, our town would be filled with more cottonwood trees than maples and oaks combined. The soft sounds of those spade-shaped leaves rustling in the slightest breeze might serve to slow us Yankees down a bit. Lulled by cottonwoods, we might become more Western in outlook. Less rushed and more leisurely.

But we are bound by the familiar cycle of our Northeastern climate and seasonal change. Now that spring is in full flower, we don’t want to miss a thing.

While I was making the rounds of my garden last week paying homage to my perennials and reveling in the lush green growth all around, I noticed a swooping movement overhead. Tree swallows were making their own tour of the open space at the far end of the lot.

Their wheeling flight was accompanied by much chattering and tweeting as though they approved of all that blue sky above, and their aerial acrobatics were centered around an unoccupied bluebird house standing alone on a hillside.

I had just about given up on that house since only English sparrows seemed interested in it. Over and over again I had removed the sparrow proto-nests before they got big enough to prompt egg- laying. Six removals later and those persistent sparrows were still shoving more grass in there. We were locked in a battle of wills.

Feeling only slightly guilty, I was determined to discourage the aggressive, nonnative English sparrows, mainly because they prey on bluebirds. They not only usurp bluebird nest sites, they will actually kill a female bluebird while she is sitting on her eggs. I didn’t want any part of providing housing for the next generation of English sparrows.

The possibility of tree swallows was something I had never considered. I knew the species shared bluebirds’ preference for nest boxes even down to the size of the entrance hole –– which must be exactly one and a half inches in diameter. And who could not admire tree swallows for their dark blue, iridescent-colored backs and snow-white breasts, as well as for their fantastic flight displays.

We would all benefit from their fondness for insects caught on the fly –– moths, ants, mayflies, beetles, horseflies, mosquitoes. The swallows would help control insect numbers in a manner more environmentally friendly than any application of pesticides could ever be.

Gratefully, I watched while the male tree swallow buzzed and dive-bombed the male English sparrow who was complaining loudly from a nearby rock. While her mate flew interference, the female tree swallow settled into the box and assumed a most domestic stance perched at the edge of the entrance hole looking out. As for the English sparrow and his mate, they fled the territory and have not come back.

Now I’ve added one more stop to my daily garden tour, and it’s not about removing English sparrow nests. Instead, I’m celebrating the serendipitous presence of tree swallows nesting in my bluebird box and watching for their single brood of six to eight babies that will hopefully hatch sometime in July.

I know the tree swallows started housekeeping right away because when I peaked inside the box, there was a single feather placed in the bottom as though to reserve the room.