Winter Wren (with the amusing Latin name troglodytes troglodytes) sometimes roosts communally when cold weather hits. Although unusual, roosting groups can be large; more than 30 wrens were found in one nest in Washington State, USA.
A Winter Wren: One of England's Well-Loved Birds! This is actually a Carolina Wren, identified as such by the warm reddish brown back, buffy underparts and white stripe above the eye. This bird is also much bigger than a Winter Wren.