The wren typically forages on the ground or in low vegetation, creeping around the forest floor in short, rapid hops which can make it appear more like a mouse than a bird (4) (5) (7). It generally flies only short distances, with very rapid wing beats, and often bobs the head and body up and down when perched (4) (7). The diet of the wren consists mainly of invertebrates, including insects, insect larvae, spiders, millipedes and sometimes snails (2) (3) (4) (6). It has been known to take vertebrate prey, such as small fish, tadpoles and young frogs, and also eats some plant food, including berries, seeds and even seaweed (3) (4). The wren searches methodically for food amongst vegetation, dead wood, roots and other nooks and crannies, and will also snatch insects from the air or even immerse its head in water in search of aquatic prey (2) (3) (4).
The breeding season of the wren usually begins in March or April in Western Europe, but is slightly later in Central Europe, Russia and northern North America (3). Male wrens are highly territorial throughout the year (4). The males may mate with several females in some areas, although monogamy is more common in North America (3) (4). The wren frequently builds its nest in a hole or crevice, such as an old woodpecker hole, a natural tree cavity, a rock crevice, or a hole in a bank, or it may create a free-hanging structure on a branch, log, root mass, building, or underneath a bank of moss (2) (3) (4) (5). This species has also been known to nest in unusual locations such as the pocket of a hanging coat or in a bundle of rope (3) (4).
The nest of the wren is built by the male, and typically consists of a dome of grass, moss, twigs, bark, rootlets, feathers and hair, usually lined with feathers and with an entrance hole at the side (2) (3) (4) (8). The scientific name of this species, troglodytes, means “cave dweller”, alluding to its habit of building enclosed nests, and probably also in reference to its rather skulking and secretive behaviour (8). Each male constructs several different nests, and the female then selects one to use for breeding. It is the female that adds the nest lining. The nest site may be reused over a number of years, and the wren will also use surplus nests for roosting (2) (3) (4) (8). In cold weather, many individuals may roost in the same nest (2) (4) (8), with a record of 31 wrens packing into one nest box in western Washington, USA (2).
The wren lays between one and nine eggs, which are white with reddish-brown spotting (2) (3) (4). Only the female incubates, and the eggs hatch after about 16 days. The young wrens are fed by both adults and leave the nest after 14 to 19 days, after which they are fed for a further 9 to 18 days before becoming independent. The breeding pair may go on to raise a second or even a third brood in the same season (3) (4). The oldest wren has been recorded living to over six years of age (4).