Xenicidae, formerly Acanthisittidae, bird family of the order Passeriformes; its members are commonly known as New Zealand wrens. The three living species are the rock wren (Xenicus gilviventris) and the rare bush wren (X. longipes) on South Island and, common to both islands, the rifleman (Acanthisitta chloris). A fourth species, the Stephen Island wren (X. lyalli), was discovered in 1894 by a lighthouse keeper and killed soon afterward by his cat. Nine specimens, brought home by the cat, were sent to the British Museum. This may have been the only flightless passerine bird; certainly its distribution—less than one square mile on an island in Cook Strait—was astonishingly limited.
Xenicids are tiny birds of stout build, with a nuthatch-like bill and an extremely short tail. They vaguely resemble pittas, with which they may share ancestry. The rifleman, only eight centimetres (three inches) long, has brown and yellow plumage suggesting the uniform of an early-day British rifle corps. It is a tree-creeping species found mainly in beech forest. The bush wren is also an arboreal insect eater. The rock wren feeds chiefly in mountains on open slopes. Both wrens bob up and down vigorously on alighting, and the rifleman is a constant wing quiverer.