Wrens are noted for using a wide variety of cavities in human artifacts for their nests, but this is the first time I've seen it here--and to turn down that carefully cleaned and hung box, so well-situated, away from the main drag.
From Birds by Bent:
Other interesting nesting sites of the house wren have been in a fish creel or watering pot hung on the side of a shed or fence, rusty tin cans in garbage piles, old threshing machines and other farm machinery, in tin cans, teapots, and flowerpots left on shelves of sheds, in a soap dish, in old boots and shoes, and even in a bag of feathers. Outdoors they have been known to nest in the nozzle or main part of pumps, in the hat or pockets of a scarecrow, in an iron pipe railing, in a weather vane, in holes in a brick wall or building, and in a coat hung up at a camp site. One pair of wrens built their nest on the rear axle of an automobile which was used daily. When the car was driven the wrens went along. Even under these most unusual circumstances the eggs were successfully hatched (Northcutt, 1937).
One thing I noticed having them so close at hand was all the conversation that went on between the pair, while, I guess, the nest was being perfected and the female was sitting on eggs. All the sounds were wren-like, but very complex at times. Even a few days ago, when feeding and poo-removal (pictured at the right) was going strong, I'd hear one or another of the wrens in the nearby spruce producing a catbird-like cacophony of squeaks and chatters.
And there's lots of scolding too, of course. Though the only chasing I've seen was of a chickadee, the only other cavity nester that's happened into the vicinity of the nest since it's been active, which I speculate is the reason the wren chased it, while tolerating the robins, cedar waxwings, blue jays, and various others who've been around. I'm surprised by the tolerance shown the bluejays, which have been particularly numerous (and noisy) around the yard this year, but perhaps they pose no threat. Obviously the opening into the watering can is much larger than that of the standard nest box, but inside (unfortunately I haven't been able to photograph this) there is a "vestibule" of a few inches, and then a wall of sticks, with just a small open space between its top and the wall of the can, that hides the nest. It seems possible that this arrangement would prevent most avian nest predators from gaining access.
Hummingbird numbers are way up just now as the young are out of their nests and into the feeders, also around the patio. The wrens don't chase the hummingbirds, but one day I did see a hummingbird chase one of the wrens. It'll seem awfully quiet when they've both gone south--won't be long now.