A small brown bird, the Wren, also called Eurasian Wren, is common but secretive, foraging for insects in the undergrowth. Shown here with characteristic upturned tail.
Not Britain's/Europe's smallest bird, -- see Goldcrest link below. Wrens will eat spiders' webs in winter when insects are in short supply.
The Wren has a remarkably loud voice for its size
and uses it to call for a mate and to warn of danger