A swallow observer sees a little bit of everything.

On April 22 the ice on Assawa Lake, the small shallow lake behind my house, was nearly ice-free, save for a sheet of ice floating on the larger and deeper portion of the basin. I’m confident that I could’ve canoed completely around the basin had I wanted to.

As I took a short walk to the shore of the lake during my noon-hour, I heard the familiar tinkling vocalizations of a bird I haven’t heard since late last summer—a tree swallow. Glancing to my left at a bluebird house that I have installed on a post not far from the lake, a tree swallow was clinging to the nest box and looking into the entrance.

Gripping the birdhouse in woodpecker-like fashion, the vocal swallow examined the entrance as it poked its head inside for a look. A moment later the tree swallow entered the birdhouse and then quickly exited and flew off.  

Tree swallows are stocky, broad-winged swallows with snow-white breasts, giving them an almost penguin-like appearance when perched with folded wings.  Widespread amongst all swallows, tree swallows, like purple martins, choose tree cavities and artificial nest boxes for nesting and raising offspring.  

As swallows go, tree swallows are aggressive, especially the males when defending their nesting territory.  The species’ assertiveness is undoubtedly a primary reason why tree swallows are known to out-compete eastern bluebirds for suitable tree cavities and birdhouses.

Therefore, because of this behavior, it’s advisable to erect pairs of bluebird houses at a distance of no more than 10 to 20 feet apart, or back-to-back on the same post.  Thus, since tree swallows don’t allow other tree swallows to nest within 20 feet, the other nearby birdhouse is free for a nesting pair of bluebirds to use. The tactic doesn’t always work, but it is a proven way to combat tree swallow takeovers of bluebird houses.

Tree swallows can be found throughout all of North America and as far north as Alaska. Here in Minnesota, tree swallows are one of the most common migrants. Vocal and acrobatic on-the-wing, these delightful birds are expert aerial hunters as they dart and dive while capturing flying insects as they go. 

Breeding and nesting near open fields and wetlands, tree swallows are easy to distinguish from most other species of birds as their beautiful bluish backs and white breasts set them apart. As well, tree swallows are one of the few birds that skim the surface of water on lakes and wetlands while in flight. Whereas most birds take their baths standing in a puddle or birdbath, tree swallows take their baths by gracefully flying over a body of water, dipping to the surface, and quickly skimming their bodies on the water as they fly.

I’ve enjoyed many times watching groups of tree swallows on calm evenings taking their baths on the surface of Assawa Lake. After they skim a patch of water and quickly gain altitude, it’s not uncommon to see the birds gently shake themselves of excess water that their feathers might’ve collected. 

As mentioned, tree swallows are cavity nesters. These special swallows will normally choose abandoned woodpecker holes in trees, or other makeshift tree cavities, for making their nests inside of, but they will readily use birdhouses, too. Materials that tree swallows use to construct their nests include mostly grasses and other plant materials, but will always be lined with several feathers from other species of birds.  Four to seven eggs are laid that take about a month’s time from laying, incubating, hatching, and fledging. Up to two broods can be raised per season. 

Tree swallows have returned. Watch for them if you haven’t seen one yet, because they’ve just begun trickling back to the Northland. Look for courting pairs carrying feathers in their beaks, a sure sign that you’re witnessing the welcoming sight of springtime tree swallows as we get out and enjoy the great outdoors. 

Blane enjoys getting feedback from readers and hearing about your stories from Minnesota’s great outdoors. Email him at bklemek@yahoo.com.