Toutouwai (North Island robins Petroica longipes) on Aotea/Great Barrier Island

KEVIN PARKER (Parker Conservation Ltd)

Toutouwai, or North Island robins (Petroica longipes), were once widespread throughout forested areas in Te Ika a Maui, the North Island, Aotearoa New Zealand. However, they have declined since human settlement because of the extensive loss of their forested habitats and the introduction of exotic mammalian pests, especially ship rats (Rattus rattus). They are now mainly confined to colder and wetter forests in the central North Island, along with large natural populations on Kapiti Island and Hauturu o Toi/Little Barrier Island(1).

Toutouwai have been extensively translocated to protected islands, and mainland sanctuaries, under varying levels of pest management. Translocation outcomes have been variable. Some sites maintain large thriving translocated populations while others are small with little population growth. Some have failed, despite small numbers of individuals persisting for 10-20 years(2),(3).

Toutouwai were translocated to Aotea/Great Barrier Island with releases at the Little Windy Hill Sanctuary in 2004, 2009 and 2012 and Glenfern Sanctuary in 2005, 2009, 2012(2). Despite excellent pest control, and successful breeding at both sites, these translocations ultimately failed. By 2016 there were no longer toutouwai present at either site. However, there have been consistent reliable reports of toutouwai since 2007 from Wildlife Management International teams and Department of Conservation staff working in the black petrel/ tākoketai (Procellaria parksoni) breeding colony on Hirakimata, the highest point on Aotea. There is also a population of North Island tomtits/miromiro (Petroica macrocephalus toitoi) on Hirakimata, along with consistent reports of red-crowned kākāriki (Cyanoramphus novaezelandiae) and korimako/bellbirds (Anthornis melanura).

Given these sightings, Judy Gilbert, from the Windy Hill Rosalie Bay Trust, secured funding for surveys at Hirakimata in 2022, 2023 and 2024. So in April of each year I loaded my pack with supplies and toutouwai catching gear and headed up Hirakimata to survey the birds.

While up on Hirakimata I walked the main tracks, along with research tracks and pest lines, playing toutouwai calls and looking and listening for birds, along with revisiting sites where I had seen or caught birds in previous trips. It is big steep country up on the maunga and toutouwai are not a big bird. However, they have two characteristics that help in locating them. First, the males give loud territorial calls that can be detected from some distance. Second, they are an incredibly curious bird and will come in and investigate if they hear me moving through the bush.  

When I found a toutouwai I would record its leg band combination, its location, and feed it with mealworms, a toutouwai delicacy. If it was unbanded, I would bait a small trap with a mealworm and attempt to catch the bird, band it, sex and age it, and give it a brief health check. It would then be released at the point of capture. Most birds get over capture very quickly and will readily approach me again, often within minutes, for a mealworm treat. However, despite coming within millimetres of the trap, they will not enter it again willingly, which is hardly surprising.

Each year I would typically encounter 12-20 birds, a mix of banded birds from previous years and unbanded birds that either evaded capture the previous year, or juveniles from the breeding season prior to my annual visits. All of the toutouwai I encountered appeared healthy, and in good condition.

Miromiro/North Island tomtits are also abundant and were frequently encountered while on Hirakimata, along with two to six red-crowned kākāriki, black petrels and the occasional Cook’s petrel. Unfortunately no korimako/bellbirds were heard or seen on any of my visits over the three years.

The results of these surveys are encouraging because despite the unsuccessful translocations to Windy Hill and Glenfern a small population of toutouwai has established on Hirakimata. This is almost certainly a result of the combination of a colder and wetter climate at elevation on Hirakimata, along with cat (Felis catus) and rat control to protect black petrels. Together, these factors provide some protection for the small toutouwai population and, assuming this continues, the toutouwai population on Hirakimata is likely to persist. This is especially so given that the toutouwai distribution neatly matches that of the trapping network maintained by DOC.

Therefore, the most important management action to maintain toutouwai on Hirakimata will be to maintain the current trapping network. If resources allow, the network could be intensified by using for example, additional traps and more frequent checks. Ideally this would align with the onset of toutouwai breeding (August-January) when toutouwai are most sensitive to rat and cat predation. Intensified control would also further protect black petrels, Cook’s petrels (Pterodroma cookii) and other threatened species on and around Hirakimata.  

Some toutouwai are almost certainly dispersing downslope to unmanaged areas. Unfortunately, while males that disperse could likely persist for many years, females are unlikely to survive through the breeding season because of intense rat predation (Parlato and Armstrong 2012, 2013). However, these dispersing birds could be further protected by expanding pest control beyond the current network. This would allow for the expansion of the Hirakimata toutouwai population, along with miromiro, kākāriki and korimako.

Ultimately, if the area under pest control increases, threatened bird species, along with lizard, invertebrate and plant species, will be able to expand their local ranges. This might also allow for the reintroduction of several missing species, including popokatea (Mohoua albicilla) and kōkako (Callaeas wilsoni) and, if a pest free Aotea can ever be achieved, even the most pest sensitive bird species such as North Island tīeke (Philesturnus rufusater), hihi (Notiomystis cincta) and kākāpō (Strigops habroptilus).

 Hirakimata is an outstanding remnant of mixed podocarp forest and Aotea more generally contains many rare species and ecosystems. The removal of key pest species, especially ship rats and cats, will allow the motu to be restored to an ecosystem resembling its former ecological glory, along with being a further point of pride for the islanders who call Aotea home.      

Acknowledgements

Biz Bell and her Wildlife Management International Team first documented the presence of toutouwai on Hirakimata in 2007 and kept records of birds that were very useful for my surveys. DOC Aotea Great Barrier, especially Sue Moore, have been also very helpful in providing information while working on Hirakimata. Finally, Judy Gilbert, a true champion for conservation on Aotea, funded this work and provided support throughout.

References

1. Heather B, Robertson H 2015. The field guide to the birds of New Zealand. New Zealand, Penguin NZ.

2. Miskelly CM, Powlesland RG 2013. Conservation translocations of New Zealand birds, 1863-2012 Notornis 60: 3-28.

3. Richardson K, Doerr V, Ebrahimi M, Parker KA 2015. Considering dispersal in reintroduction and restoration planning. In: Armstrong DP, Hayward MW, Moro D, Seddon PJ ed. Advances in Reintroduction Biology of Australian and New Zealand Fauna. Australia, CSIRO Publishing. Pp. 59-72.

4. Parlato EH, Armstrong DP 2012. An integrated approach for predicting fates of reintroductions with demographic data from multiple populations. Conservation Biology 26: 97-106.

5. Parlato EH, Armstrong DP 2013. Predicting post-release establishment using data from multiple introductions. Biological Conservation 160: 97-104.

6. Caughley G 1994. Directions in conservation biology. Journal of Animal Ecology 63: 214-244.