Thursday 24 July, 2008
Endemic alpine bird declining
A recent study shows the rock wren or tuke is declining in numbers and in range.
Sue Michelsen-Heath (University of Otago) and Peter Gaze (Department of Conservation) have studied all known records of the diminutive and unique alpine bird and published their findings in the journal Notornis.
Over 2100 records were gathered from between 1912 and 2005 from a wide range of sources including
DOC, the Ornithological Society of NZ (OSNZ) and tramping and alpine clubs, prominent naturalists and many nature enthusiasts.
A map of all rock wren sightings shows a 24% reduction in the area they have been found in since 1984. Gaze said “It could be that local populations are so low they are not being spotted. The birds are also hard to detect because of their small size and their camouflage. This makes it difficult to quantify changes in population size.”
Michelsen-Heath said “Changes in the popularity of different types of outdoor recreation over the pastcouple of decades has contributed to a reduction in rock wren reportings. But predation by mice and stoats is the main factor.”
Fewer reports of rock wren sightings could be due to fewer people doing once popular exploratory tramps.More people are kayaking and white-water rafting. Furthermore, DOC now uses contractors to maintain back-country tracks so many staff are not regularly out in these remote areas.
Gaze said “It could be that they are no longer present in some areas, or that people aren’t looking as hard, or perhaps people are not reporting sightings or visiting some of these areas anymore.”
Michelsen-Heath said that consistent anecdotal accounts of decline, evidence of predation by stoats and mice, unsuccessful searches in previous strongholds, and the recent post settlement extinction of five other New Zealand wren species are a real concern and do not bode well for the bird’s future.
The study’s authors also hold fears for the effect climate change on the species. Rats may start colonising alpine areas as these areas become warmer, and prey on rock wren. It is unknown how climate change could affect the diversity and abundance of insects that the bird feeds on.
Michelsen-Heath said “We’d love to see regular reports of birds coming in from trampers, climbers, hunters and outdoor adventure guides, as well as from DOC staff and bird watchers, showing the birds are still alive and well in these areas.”
“The more records we receive, the more confident we will be that we’ve got the real picture” said Gaze.
The public should report sightings of rock wren including a GPS or map reference to their local DOC office, or enter their recording directly into eBird – OSNZ’s online database (www.eBird.com/nz).
Gaze said “The results confirmed what we had expected. People were saying they weren’t seeing them as often, or weren’t seeing them where they had in the past. So we tried to look at anecdotal evidence scientifically. The results give us justification to be concerned.”
• Results show that rock wren may have disappeared from: Douglas Range in Kahurangi National
Park, Kaikoura Mountains, Paparoa National Park and Lewis Pass.
• Numbers appear to be declining in: Mt Aspiring National Park, Henderson Range in Kahurangi
National Park, Murchison Mountains.
• The remoteness, high altitude and vastness of the Southern Alps make it extremely difficult to
control predators such as stoats and mice. Currently there is no way to control these pests on a large scale within rock wren habitat.
• With the help of a large donation, DOC has translocated some rock wren onto two predator-free
islands in Fiordland.
• How to identify rock wren: Smaller than a silvereye, but with similar colouring. Males are olivegreen,females are more slatey-brown below, have a very short tail, long legs, rounded wings and destinctive cream ‘eyebrows’. They can be identified by their high-pitched, simple three-note call.
• Where rock are found: Alpine basins of the Southern Alps, among rock falls, scree slopes and
• Rock wren behaviour: It bobs up and down among rocks and subalpine scrub feeding on small
insects. It runs and hops and only flies short distances. It nests in holes.
• The only ‘true’ alpine bird in NZ, breeding and living in the alpine zones all year round.
• The rock wren or tuke (Maori name) is endemic to NZ meaning it is a native species and found only in NZ.
• Rock wren are classed as 'nationally vulnerable’, one of three criteria for threatened species in NZ. This status is due to the relatively small total population and the expected continued decline in abundance. Rock wren’s global status is ‘globally threatened.
• The rock wren belongs to a distinct family [actually ‘Infra Order’] of birds that is known only from NZ. A hundred years ago there were five species in this family but now the rifleman and rock wren are the only survivors. The rock wren and rifleman’s ancestors separated from all other bird families about 90 million years ago.
• Notornis is a scientific journal published quarterly by the Ornithological Society of New Zealand