The Eurasian Wren (Troglodytes troglodytes), is a very small bird, and the only member of the wren family Troglodytidae found in Eurasia.
The scientific name is taken from the Greek word “troglodytes” (from “trogle” a hole, and “dyein” to creep), meaning “cave-dweller”, and refers to its habit of disappearing into cavities or crevices whilst hunting arthropods or to roost. The taxonomy of the genus Troglodytes is currently unresolved, as recent molecular studies have suggested that Cistothorus spp. and Thryorchilus spp. are within the clade currently defined by Troglodytes.
The 9- to 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.
The plumage is subject to considerable variation, and where populations have been isolated, the variation has become fixed in one minor form or another. There are around 27 subspecies of this taxonomically complex bird. The disputed subspecies orii, the Daito Winter Wren, became extinct around 1940 – if it is indeed a valid taxon and not merely based on an anomaly.
In most of northern Europe and Asia, it 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