T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Wren (Rock) Xenicus gilviventris

Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Suborder: Acanthisitti
Family: Acanthisittidae
Genus: Xenicus
Species: X. gilviventris
Binomial name: Xenicus gilviventris
Common name: New Zealand rock wren, rock wren, South Island wren, pīwauwau, mātuitui, tuke.

Xenicus gilviventris is a small New Zealand wren endemic to the South Island of New Zealand. The rock wren is currently restricted to alpine and sub alpine areas (900–2500 m altitude) of the Southern Alps, the TasmanMountains of Northwest Nelson, and the Victoria Range of Westland, all in the South Island.
It is a poor flier and highly terrestrial, feeding in low scrub, open scree, and rock falls. The rock wren and rifleman are the only two surviving New Zealand wrens. Its current alpine distribution is a habitat where few rodents can survive. Their preferred habitat is close to the tree line, amongst rock falls, scree, fellfield, and low scrub. Rock wrens, unlike many alpine birds, do not migrate to lower elevations in winter, instead, they seem to shelter and forage in rock falls beneath the snow layer.

The rock wren is a very small, almost tailless bird that prefers to hop and run on its long legs, and uses its rounded wings to fly only short distances. They rarely fly more than 2 m off the ground or for distances of more than 30 m. Males are 16 g, females 20 g. Males are greenish with yellow flanks and a pale underside, females tend to be browner, although the degree of difference between the sexes varies geographically. airs maintain a year-round territory, and work together to build a large enclosed nest with an entrance tunnel. The nest is lined with feathers, often from other species of birds. Guthrie-Smith recovered 791 feathers from one nest in the 1930s, most from weka, but including some kiwi, kakapo, kea, and kereru. Rock wrens are such assiduous collectors of feathers that their nests have been checked for kakapo feathers, to determine if those endangered parrots are in the area. Three eggs are laid in late spring and incubated for three weeks. Chicks take about 24 days to fledge and are fed for at least 4 weeks. Rock wrens mostly eat invertebrates on the ground, but will sometimes take berries and seeds, and even nectar from flax flowers.

Xenicis gilviventris, showing distinctive green, yellow, and grey colouring. 

Thanks to Wikipedia for text and information