I've always had a thing for bluebirds. Their plumage is an extraordinary color, much more delicate than you find on blue jays, or even kingfishers on Lake Lillinonah — and have much nicer personalities, too, bluebirds never scold. Even their songs and calls are sweet: the website just hyperlinked, above, characterizes bluebird vocalizations as “a series of melodious, gurgling whistles sometimes sounding like cheer, cheer, cheerful, charmer.”
So one of the first things I did after moving to Brookfield was put up a bluebird house. A pair was already hanging out, feeding on caterpillars and insects, in one of our backyard maple trees... and sure enough, they soon nested in the purpose-built box. Which, having been a City Boy for a few years, I'd mounted on a tree.
Bad idea: the grey squirrels attacked, gnawing at the opening until it was wide enough to climb in and eat the eggs. Needless to say, the bluebirds decamped.
The following year I put the birdhouse on a pole, and as I recall, we (it's hard not to say “we”) had at least one successful brood. A couple years later, I won a beautiful, hand-made, painted-and-shingled birdhouse at a Housatonic Habitat for Humanity fundraiser, and bluebirds occupied that one, too.
Until, at least, the trouble started. Although I was a hardcore bird-watcher in my youth — at 14 I spent my birthday money on Arthur Cleveland Bent's complete Life Histories of North American Birds, all 21 volumes (most of it now available online) — I was still innocent about house wrens being, well, agents of the devil.
They dart about like brown sprites, have cute stubby tails, and are enthusiastic, full-throated singers: how could such creatures be evil? And yet they're notorious, it turns out, for squatting — for invading other birds' nests, destroying the eggs and moving in. Their typical victims? Bluebirds, who also nest in tree cavities, and play George McFly to the wrens' Biff Tannen.
At least that's how things played out at my house, until I bought yet another birdhouse and put it on a pole, in the lawn, well away from trees, buildings and undergrowth. There's a reason conservationists put bluebird boxes in the middle of fields: that's where the bluebirds find dinner and what wrens avoid, as they prefer skulking in the undergrowth (when not loudly warning others to stay away from their ill-gotten nest, that is).
The ploy worked: last year a pair of bluebirds raised a family there... though we hardly noticed, because the nest is so far from the human house.
The jury is out for this year. We've seen a few bluebirds around, but no sign of nesting, yet. But I can't blame the wrens; they're ensconced in the original bluebird box, from which I often hear very cute squabbling from the young nestlings. I'm happy for that: wrens are always welcome here, provided they don't drive away their betters.
Less welcome are the house sparrows, Enemy Number Two among nesting bluebirds (yes, things get violent — there's even a webpage devoted to house sparrow-on-bluebird attacks).
The sparrows — actually a kind of finch and non-native, having been brought over from Europe — haven't assaulted the new bluebird house, yet: for the third year in a row they're nesting, instead, in a corner of our retractable awning. I prefer that to a wasp nest — we've had those in the awning, too — but if the house sparrows think I'm going to put a box up just for them... well, they'll be waiting a looooooooooooong time.