And finally, any bluebird box where house sparrows are allowed to successfully produce young is worse for bluebirds than no box at all. The Jenny Wren, more commonly known as the House Wren, is one of those birds that is an annoyance and an enjoyment to bluebird enthusiasts. These birds' determination at filling all available nest boxes is matched only by their exuberant singing. The house wren, ranging from the Atlantic to the Pacific coast, and from Canada south to Argentina, is New York's most common and plainest wren. They can be found in low, deciduous woods and woodland edges, but are also quite common in yards, parks and gardens.
House wrens are cavity nesters like the bluebird.
They prefer natural cavities and woodpecker holes, but readily occupy nest boxes - especially those located along shrubby woodland edges. These energetic birds are also opportunists, and have been known to nest in flower pots, old boots, tin cans, shoes, deserted nests of other birds, and even under cars. They almost always return to a territory where they have previously nested successfully. Like bluebirds, male house wrens arrive before the females - usually in late March or April. Upon return, males will establish their territory by singing and by building stick nest foundations.