The rock wren belongs to the Acanthisittidae, the New Zealand Wrens, an ancient and taxonomically very significant family once comprising at least seven species in five different genera.
The rock wren Xenicus gilviventris is a diminutive, ground-feeding passerine found only in mountainous regions along or close to the Southern Alps of the South Island of New Zealand.
Remaining throughout its life above bush-line, the rock wren is New Zealand's only true alpine bird species. It occupies a specialised niche in an environment typified by harsh climatic conditions and rugged terrain. Work on rifleman, the only other remaining New Zealand Wren, has been limited to a dozen or so authors and all is descriptive of their biology and behaviour with no investigation of trends in abundance or distribution having been completed. Published work on rock wren is even more limited (Michelsen-Heath and Gaze in prep).
In the last five years there has been a study into changes in distribution (Michelsen-Heath and Gaze in prep), an attempt to establish a new population on Anchor Island, Fiordland (Willans and Weston, 2005) and a study into changes in abundance in the Murchison Mountains, Fiordland (Weston pers.comm).
It was difficult to obtain consistent counts of rock wren, nevertheless, the population appears to have varied from a high of 29 in 1986 to a low of 10 in 2004-05 with a spectacular recovery to 23 in 2005-06. The resighting of banded rock wren has revealed a female at least 6 years old. Only one banded bird has been re-sighted beyond the area of contiguous favourable habitat in which it was banded.