The Winter Wren (Troglodytes troglodytes), also known as the Northern Wren, is a very small bird, a member of the mainly New World wren family Troglodytidae. It is the only one of nearly sixty species in the family which occurs in the Old World; in Europe it is commonly known simply as the Wren. They are noteworthy among songbirds both because of their amazingly long and complex songs and because they are one of the few passerine species that has a distribution spanning both North America and Eurasia.

It occurs in Europe, a belt of Asia from northern Iran and Afghanistan across to Japan, and North America. It is only migratory in the northern parts of its range.

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. 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 . A study of individuals in an overlap zone between two divergent subspecies of winter wren in North America (Troglodytes troglodytes hiemalis in Eastern North America and Troglodytes troglodytes pacificus in Western North America), which differ substantially in song and genetics, found strong evidence for reproductive isolation and suggested that the pacificus subspecies be promoted to the species level designation of Troglodytes pacificus .

Description

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.

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 Eurasian subspecies of this taxonomically complex bird, with around 12 more in North America. 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.

Thus in the British Isles, in addition to the typical bird, T. t. indigenus, there are two distinct insular forms; one, T. t. hirtensis, is confined to the island of St Kilda, and another, T. t. zetlandicus to Shetland. The St. Kilda Wren is greyer above, whiter beneath, and with more abundant bars on the back; the Shetland Wren is darker.

Taxonomy

Recent taxonomies of the Troglodytes genus have shown that winter wrens are the most distantly related of all species within Troglodytes, and have shown that two other groups, the timberline wren (Thryorchilus browni) and the four species within the genus Cistothorus, are within the clade defined by all of the Troglodytes. To make Troglodytes monophyletic, Rice et al. (1999) proposed that winter wrens could be placed in their own genus, Nannus. Alternatively, as suggested by Gómez et al. (2005) , Troglodytes could be made more inclusive by assigning the Troglodytes genus to the current Thryorchilus and Cistothorus genera.

By studying the songs and genetics of individuals in an overlap zone between two subspecies of winter wren within North America (Troglodytes troglodytes hiemalis in Eastern North America and Troglodytes troglodytes pacificus in Western North America), a study by Toews and Irwin (2008) found strong evidence of reproductive isolation between the two. It was suggested that the pacificus subspecies be promoted to the species level designation of Troglodytes pacificus with the common name of "?Pacific wren'. By applying a molecular clock to the amount of mitochondrial DNA sequence divergence between the two , it was estimated that Troglodytes pacificus and Troglodytes troglodytes last shared a common ancestor approximately 4.3 million years ago, long before the glacial cycles of the Pleistocene, thought to have promoted speciation in many avian systems inhabiting the boreal forest of North America .

Ecology

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.

Individuals vary in quality as well as volume of their song. The song begins with a few preliminary notes, then runs into a trill, slightly ascending, and ends in full clear notes or another trill. At all and any season the song may be heard, though most noticeable during spring. Despite its generally mouse-like behaviour, the male may sing from an exposed perch as its whole body quivers from the effort.

At night, usually in winter, it often roosts, true to its scientific name, in dark retreats, snug holes and even old nests. In hard weather it may do so in parties, either consisting of the family or of many individuals gathered together for warmth.

For the most part insects and spiders are its food, but in winter large pupae are taken and some seeds.

Breeding Winter Wren with 4 hatchlings, having fed one a spider

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.

Myths and legends

According to European folklore, the Wren is the King of the Birds. Long ago the birds held a contest to see who could fly the highest; at first it looked as though the Eagle would win easily, but just as the Eagle began to tire, the Wren, which had hidden under the Eagle's tail feathers, crept out and soared far above. The wren's majesty is recognized in such stories as the Grimm Brothers' The Willow-Wren and the Bear.

The Wren also features in the legend of Saint Stephen, the first Christian martyr, who supposedly was betrayed by the noisy bird as he attempted to hide from his enemies. Traditionally, St. Stephen's Day (26 December) has been commemorated by Hunting the Wren, wherein young Wrenboys would catch the bird and then ritually parade it around town, as described in the traditional Wren Song. The Wren, the Wren, the king of all birds, St. Stephen's day was caught in the furze. Although he is little, his family's great, I pray you, good landlady, give us a treat.. The tradition, and the significance of the Wren as a symbol and sacrifice of the old year, is discussed in Sir James Frazer's The Golden Bough.

In popular culture

• In The Jungle Book by Rudyard Kipling, Limmershin, the Winter Wren, is the narrator of the "The White Seal" story .
• The German saying "jemand freut sich wie ein Zaunkönig" means "be joyful" .