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The rock wren, or tuke, is classed as nationally vulnerable, and the results of a study have shown numbers appeared to be declining in Mount Aspiring National Park, in the Murchison Mountains and in the Henderson Range in the Kahurangi National Park.
University of Otago teaching fellow Sue Michelsen-Heath, of the zoology department, studied more than 2000 sightings of the rock wren recorded between 1912 and 2005.
The results of analysing the sightings showed areas the tiny alpine bird inhabited had declined by 24% since 1984.
Predation by mice and stoats was a major factor in population decline, she said.
Anecdotal evidence of population declines, evidence of predation, unsuccessful searches in previous strongholds and the extinction of five other New Zealand wren species in the past 100 years did not bode well for the bird's future.
Department of Conservation technical support officer Peter Gaze said climate change could also affect the rock wren, as rats could start to colonise alpine areas as they became warmer.
The wren is the only true New Zealand alpine bird which breeds and lives in the alpine zones all year round.
It was difficult to quantify changes in population size as the bird was hard to detect because it was small and well camouflaged.
The rock wren is smaller than a silvereye, but has similar colouring. Males are olive-green while females are more slatey brown.
The birds have a very short tail, long legs and distinctive cream-coloured eyebrows.
They are found in alpine basins of the Southern Alps among rock falls, scree slopes and subalpine scrub. They can be identified by their high-pitched, simple three-note call.
Sightings, with a GPS or map reference, can be reported to Doc or entered on to the Ornithological Society of New Zealand's website www.eBird.com/nz.
The findings of the study were published in the society's scientific journal Notornis.