Troglodytidae – Wrens

The Troglodytidae are mostly small, brownish passerine birds in the mainly New World family commonly known as wrens. 88 species of true wrens in roughly 20 genera are described. Only the Eurasian Wren occurs in the Old World, where in Anglophone regions, it is commonly known simply as the ‘wren’, as it is the originator of the name. The name wren has been applied to other, unrelated birds, particularly the New Zealand wrens Acanthisittidae and the Australian wrens Maluridae.

Most wrens are small and rather inconspicuous, except for their loud and often complex songs. Notable exceptions are the relatively large members of the genus Campylorhynchus, which can be quite bold in their behaviour. Wrens have short wings that are barred in most species, and they often hold their tails upright. As far as known, wrens are primarily insectivorous, eating insects, spiders, and other small arthropods, but many species also eat vegetable matter and some take small amphibians and reptiles.

The Eurasian Wren is among the smallest birds in its range, while the smaller species from the Americas are among the smallest passerines in that part of the world. They range in size from the White-belliedWren, which averages under 10cm and 9g, to the Giant Wren, which averages about 22cm and weighs almost 50g . The dominating colours of their plumage are generally drab, composed of grey, brown, black, and white, and most species show some barring, especially to tail and/or wings. No sexual dimorphism is seen in the plumage of wrens, and little difference exists between young birds and adults. All haveThey have loud and often complex songs, sometimes given in duet by a pair. The song of members of the genera Cyphorhinus and Microcerculus have been considered especially pleasant to the ear.

Wrens are principally a New World family, distributed from Alaska and Canada to southern Argentina, with the greatest species richness in the Neotropics. As suggested by its name, the Eurasian Wren is the only species of wren found outside the Americas, as restricted to Europe, Asia, and northern Africa (it was formerly considered conspecific with the Winter Wren and Pacific Wren of North America). The insular species include the Clarión Wren and Socorro Wren from the Revillagigedo Islands in the Pacific Ocean, and Cobb’s Wren in the Falkland Islands, but few Caribbean islands have a species of wren, with only the Southern House Wren in the Lesser Antilles, the Cozumel Wren of Cozumel Island, and the highly restricted Zapata Wren in a single swamp in Cuba.

The various species occur in a wide range of habitats, ranging from dry, sparsely wooded country to rainforest. Most species are mainly found at low levels, but members of the genus Campylorhynchus are frequently found higher, and the two members of Odontorchilus are restricted to the forest canopy. A few species, notably the Eurasian Wren and the House Wren, are often associated with humans. Most species are resident, remaining in Central and South America all year round, but the few species found in temperate regions of the Northern Hemisphere are partially migratory, spending the winter further south.

Wrens vary from highly secretive species such as those found in the genus Microcerculus to the highly conspicuous genus Campylorhynchus, the members of which frequently sing from exposed perches. The family as a whole exhibits a great deal of variation in their behaviour. Temperate species generally occur in pairs, but some tropical species may occur in parties of up to 20 birds.

Wrens build dome-shaped nests, and may be either monogamous or polygamous, depending on species.

Though little is known about the feeding habits of many of the Neotropical species, wrens are considered primarily insectivorous, although many species also take vegetable matter such as seeds and berries; the Eurasian Wren has been recorded wading into shallow water to catch small fish and tadpoles; Sumichrast’s Wren and the Zapata Wren take snails; and the Giant Wren and Marsh Wren have been recorded attacking and eating bird eggs (in the latter species, even eggs of conspecifics). A local Spanish name for the Giant Wren and Bicolored Wren is chupahuevo (egg-sucker), but whether the latter actually eats eggs is unclear.

The Plain Wren and Northern Wren sometimes destroy eggs and the Rufous-and-white Wren has been recorded killing nestlings, but this is apparently to eliminate potential food competitors rather than feed on the eggs or nestlings. Several species of Neotropical wrens sometimes participate in mixed-species flocks or follow army ants, and the Eurasian Wren may follow badgers to catch prey items disturbed by them.