0 the winter wren (troglodytes hiemalis) is a very small north american bird and a member of the mainly new world wren family troglodytidae .
1  it was once lumped with troglodytes pacificus of western north america and troglodytes troglodytes of eurasia under the name winter wren .
2 it breeds in coniferous forests from british columbia to the atlantic ocean .
3  it migrates through and winters across southeastern canada , the eastern half the united states and (rarely) north-eastern mexico .
4  small numbers may be casual in the western united states and canada .
5 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 .
6 rufous brown above , grayer below , barred with darker brown and gray , even on wings and tail .
7  the bill is dark brown , the legs pale brown .
8  young birds are less distinctly barred .
9  most are identifiable by the pale "eyebrows" over their eyes .
10 by studying the songs and genetics of individuals in an overlap zone between troglodytes hiemalis and troglodytes pacificus , toews and irwin (2008) found strong evidence of reproductive isolation between the two .
11  it was suggested that the pacificus subspecies be promoted to the species level designation of troglodytes pacificus with the common name of pacific wren .
12  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 .
13 the winter wren nests mostly in coniferous forests , especially those of spruce and fir , where it is often identified by its long and exuberant song .
14   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 .
15 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 .
16  at night , usually in winter , it often roosts , true to its scientific name , in dark retreats , snug holes and even old nests .
17  in hard weather it may do so in parties , either consisting of the family or of many individuals gathered together for warmth .
18 for the most part insects and spiders are its food , but in winter large pupae are taken and some seeds .
19 the male builds a small number of nests .
20  these are called "cock nests" but are never lined until the female chooses one to use .
21 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 .
22  five to eight white or slightly speckled eggs are laid in april , and second broods are reared .
