New Zealand Wrens

New Zealand wrens (Acanthisittidae) are a unique family of very small birds native to New Zealand. Once comprised of seven Holocene species, only two exist today, both of which are poor fliers, adapted to foraging on insects in forests, and the rock wren being endemic to alpine regions. The family is ancient, potentially having evolved following New Zealand's separation from Gondwana around 82-85 million years ago. The taxonomy of these birds has been debated, with recent genetic studies suggesting a lineage distinct from other passerines and possibly surviving a genetic bottleneck during the Oligocene, when New Zealand was largely submerged. Notably, several species, like the stout-legged and long-billed wren, became flightless, a rare trait among passerines. Human settlement in New Zealand led to the extinction of several wren species, including the South Island stout-legged wren, North Island stout-legged wren, long-billed wren, Lyall's wren, and bushwren, mainly due to introduced predators like the Polynesian rat. Currently, the rifleman is fairly common across both the North and South Islands, while the New Zealand rock wren is confined to the alpine areas of the South Island and is considered vulnerable. New Zealand wrens typically have drab brown-green plumage, show some sexual dimorphism in size and plumage, and form monogamous pairs for breeding. They live in a range of habitats from forests to alpine zones and, like most New Zealand passerines, are sedentary with no evidence of migration. The birds’ ability to adapt is illustrated by the rifleman expanding into exotic pine plantations after their native forest habitats were reduced. The conservation status of these unique birds remains a concern due to their limited distribution and declining numbers, especially for the vulnerable New Zealand rock wren.