Don't let the dimunitive size of the rock wren (pīwauwau) fool you for a second. These tiny creatures are some of our very staunchest native birds, and one of only two remaining members of New Zealand's wren family.
Rock wrens, as their name suggests, mostly exist in rocky and craggy areas high above the bushline. The first time I saw them, I was rock-climbing at Sebastopol Bluffs near Mount Cook Village, and as I heaved and struggled my way up the rock, a pair of wrens hopped and flitted around me with ease. Their busy nature, constantly exploring and poking around in their rocky habitat, coupled with their hard-case constant bobbing up and down was a pleasure to watch.
Rock wrens are New Zealand's only true alpine birds that live their entire lives above the bushline in sometimes very difficult climactic conditions, where other birds simply wouldn't stand a chance.
There were once seven species of wren in New Zealand, and now only the rock wren and its cousin the rifleman remain. Our tiny wrens didn't fare well after people and their pests arrived.
The New Zealand bush wren was once widespread throughout the country, but in a familiar tale the introduction of rats and then stoats was the death knell for these wee almost-flightless birds. They disappeared from the North Island around 1911, and in the South Island were last seen in the 1960s in Arthur's Pass. The wren found on Stewart Island is the subject of that awful conservation story where a rat plague got on to Big South Cape Island, wiping out many species including the saddleback and the greater short-tailed bat and despite the rangers' best efforts to translocate a few of the precious wrens, they too were lost to extinction.
The rock wren's breeding habits also give us glimpses at other parts of our conservation history. In his 1936 book Sorrows and Joys of a New Zealand Naturalist, William Herbert Guthrie-Smith described finding kākāpō and kiwi and weka feathers throughout the nest of a rock wren near Te Anau, indicating that those birds were probably plentiful at that time. Of course kākāpō have been extinct from that area for many decades now, but the nest of the rock wren told a marvellous story of the wildlife present at that time. Guthrie was hopeful that rock wrens were high enough at altitude that they might survive in the presence of predators.
"Xenicus gilviventris, I am glad to think, is one of the species likely to survive changes that from the forester's and field naturalist's point of view have desolated New Zealand. The ravages wrought elsewhere by deer, rabbits, opossums, birds, and other imported vermin are unlikely to affect the welfare of the rock wren."
Sadly, this was not to be the case. Our omnipresent and numerous introduced mammals made their way to alpine habitats too, putting the rock wrens at risk. The tiny size of the rock wren means that even mice can eat their eggs, so it's crucial that we provide rock wrens with suitable habitat in a predator-free environment. Currently they are listed as vulnerable under the IUCN threatened status. A recent translocation onto Secretary Island in Fiordland has already given excellent results, with unbanded (therefore new!) birds being found when scientists and rangers monitored the rock wrens after their successful translocation.
Have you ever seen a rock wren? Where? Did you know about the plight of our native wrens?