The Wren (Troglodytes troglodytes), also known as the Northern Wren, is a very small bird. In Europe it is commonly known simply as the Wren. It is noteworthy among songbirds both because of its long and complex songs and because it is one of the few passerine species that has a distribution spanning both North America and Eurasia
The 9–10.5 cm long Wren is rufous brown above, greyer beneath, barred with darker brown and grey, even on wings and tail. The bill is dark brown, the legs pale brown. Young birds are less distinctly barred.
This small, stump-tailed Wren is almost as familiar in Europe as the Robin. It is mouse-like, easily lost sight of when it is hunting for food, but is found everywhere from the tops of the highest moors to the sea coast.
In North America, most of northern Europe and Asia, the winter wren nests mostly in coniferous forests, where it is often identified by its long and exuberant song. Although it is an insectivore, it can remain in moderately cold and even snowy climates by foraging for insects on substrates such as bark and fallen logs.
Its movements as it creeps or climbs are incessant rather than rapid; its short flights swift and direct but not sustained, its tiny round wings whirring as it flies from bush to bush.
It is a bird of the uplands even in winter, vanishing into the heather when snow lies thick above, a troglodyte indeed. It frequents gardens and farms, but it is quite as abundant in thick woods and in reed-beds.
When annoyed or excited its call runs into an emphatic churr, not unlike clockwork running down. Its song is a gushing burst of sweet music, loud and emphatic. It has an enormous voice for its size, ten times louder, weight for weight, than a cockerel.
The male Wren builds several nests, up to 6 or 7 in Europe, but fewer in North America. These are called "cock nests" but are never lined until the female chooses one to use.
The normal round nest of grass, moss, lichens or leaves is tucked into a hole in a wall, tree trunk, crack in a rock or corner of a building, but it is often built in bushes, overhanging boughs or the litter which accumulates in branches washed by floods.
Five to eight white or slightly speckled eggs are laid in April, and second broods are reared. The eggs of the St. Kilda Wren are marginally larger and often more boldly spotted; six is the usual number.