The swallows here in Montana have an admirable ability to assort themselves into nesting niches. Bank Swallows live in our many sandy banks. Tree Swallows live in trees — and nest boxes. I have seen Cliff Swallows on cliffs, but even more than that, they enjoy bridges. And then there’s this guy:
Birds without a nesting site assigned to them by name seem to be a little more confused. All About Birds describes the Violet-green Swallow as a cavity nester, seen in open woods at middle elevations. Project Nestwatch elaborates: “Violet-green Swallows nest in cliff crevices, natural tree cavities, woodpecker holes, in old nests of Bank and Cliff Swallow, under the eaves of buildings, and in nest boxes.”
This made me feel a little less crazy, because until I started reading, “cavity nesters” and “middle elevations” were not terms I associated with Violet-green Swallows. I had always seen them well over my head, in rocky canyons, and given that they are an exclusively Western species, I assumed this is why.
And that’s why they caution you about assumptions. In fact, it seems like Violet-green swallows will nest anywhere they can fit in an egg and someone to incubate it. Though they face stiff competition from birds like House Wrens, to say nothing of each other, they are not without resources. In fact, they can be surprising in their subtlety: “One report documented a pair of Violet-greens assisting a pair of Western Bluebirds in raising young. The swallows guarded the nest and tended the bluebird nestlings, and after the bluebirds fledged, the swallows used the nest site.”
With such options at their disposal — everything from competition to cooperation, everywhere from woodpecker holes to rocky ledges — one wonders why this swallow remains so mysterious, and so limited in range.
Barn Swallow by David Menke, USFWS