About Xenicus gilviventris Pelzeln, 1867
Xenicus gilviventris, commonly called the rock wren, is a very small, nearly tailless bird. It prefers to hop and run using its long legs, and only flies short distances with its rounded wings. Typical body length of the species is around 9 centimetres (3.5 in). Males weigh approximately 16 grams, while females weigh around 20 grams. Male plumage is greenish with yellow flanks and a pale underside; females are typically browner, and the degree of this sexual difference in appearance varies across geographic locations. This species is currently restricted to alpine and subalpine zones, between 900 and 2500 metres in altitude, in the Southern Alps, the Tasman Mountains of Northwest Nelson, and the Victoria Range of Westland, all located in New Zealand's South Island. It is the only truly alpine bird native to New Zealand. Subfossil remains show that the species was also found in lowland forest before Polynesian settlement. DNA was extracted from remains previously believed to originate from the North Island, and when compared to DNA from South Island rock wrens, these remains were found to be more closely related to the southern South Island clade. The misidentified North Island specimen is thought to come from mislabeling by the original collector. The species' current alpine habitat has too few surviving rodents, and is filled with sheltering rocks and dense vegetation. Rock wrens prefer to live close to the treeline, among rockfalls, scree, fellfield, and low scrub. Unlike many other alpine bird species, rock wrens do not migrate to lower elevations during winter. Instead, they shelter and forage in rockfalls located beneath the snow layer.
