The unsolved riddle of the Antipodes Island snipe

Colin Miskelly (Curator of Vertebrates, Te Papa) highlights how little we know about the snipe that inhabit Antipodes Island

Antipodes Island snipe. Photo by Dave Boyle, NZ Birds Online

Antipodes Island snipe. Photo by Dave Boyle, NZ Birds Online

One of the points of interest of the remote Antipodes Islands is that they hold forms of life that are found nowhere else on the planet. Among the birds there are four such endemic forms, comprised of two species of parakeets, plus subspecies of the New Zealand pipit and subantarctic snipe. The parakeets and pipits are all in-your-face, with all three species readily seen from boats close offshore. The snipe are both scarcer and more secretive, making them not only a challenge to find, but difficult to study.

My only visit to Antipodes Island was a 5-day stay in October 1990, and I was determined to learn what I could about this most mysterious of the island’s feathered inhabitants. I had recently completed a PhD thesis study on the breeding ecology of the closely-related Snares Island snipe and Chatham Island snipe, and so arrived well-equipped to locate snipe and to interpret their behaviour and ecology – though it would have been great to have been able to stay longer!

Few New Zealanders are aware of what a snipe is, or that we have our own species of them. They formerly occurred throughout the mainland and on inshore and outlying islands. The North Island snipe was last seen in 1870 (on Hauturu/Little Barrier Island), and the South Island snipe in 1964 (on Taukihepa/Big South Cape Island, off the southern tip of Stewart Island). Both forms succumbed to introduced predators (feral cats and ship rats respectively), and the same fate befell snipe on the larger islands in the Chatham Islands, Auckland Islands and Campbell Island groups. As a result, our five surviving forms of snipe became confined to small, remote islands free of introduced rodents or cats. The one exception was that snipe managed to survive in the presence of mice on Antipodes Island – but were the snipe there affected by the presence of mice?

Antipodes Island snipe probing for food. Photo by Mark Fraser, NZ Birds Online

Antipodes Island snipe probing for food. Photo by Mark Fraser, NZ Birds Online

Snipe look and behave like miniature kiwi, but are more closely related to godwits and sandpipers. Elsewhere in the world, other species of snipe are typically found in densely vegetated wetlands – swamps and marshes. The various forms of New Zealand snipes also typically stay among dense vegetation, but occur under forest, among tussock grasslands and in herbfields on the islands they have been confined to.

Antipodes Island snipe occur at low densities all over the main island, but are almost impossible to observe among the 2-metre tall tussock on the coastal slopes. They are more readily found among the shorter grasses and ferns on the central plateau – and it was here that I was astonished to find two well-grown chicks during my October visit. The reason that I was so surprised was that during six years of study on the Snares Islands, I had never found evidence of breeding commencing before November. These two chicks must have come from clutches that were laid in August.

 

Antipodes Island snipe chick. Photo by Dave Boyle, NZ Birds Online

Antipodes Island snipe chick. Photo by Dave Boyle, NZ Birds Online

 

I didn’t have opportunities to undertake further fieldwork on snipe for the following seven years, but this all changed following a remarkable discovery in November 1997. A team of dog-handlers searching for further populations of the flightless Campbell Island teal were landed by helicopter on some of the small, sheer-sided stacks offshore from the rat-infested main Campbell Island. They failed to find any teal on 19-hectare Jacquemart Island, but did catch one snipe there. This was the first evidence that there was such a thing as a Campbell Island snipe. This was the first ‘new’ New Zealand bird to be discovered since the Westland petrel in 1945.

The then-unnamed Campbell Island snipe was clearly critically endangered, being confined to less than 19 hectares of habitat. But steps were already underway to eradicate rats from 11,000 hectare Campbell Island, 1 km away. This occurred in 2001, and within 4 years there was evidence that at least one pair of snipe had flown back to the main island from Jacquemart Island, and had bred there. I began organising a survey of the recolonising birds (which was undertaken in January 2006), and as part of my background research, started gathering all the information that I could about the likely nearest relatives of the Campbell Island snipe – namely the subspecies of subantarctic snipe that occur on the Auckland Islands and Antipodes Islands.The main source of information was in the notebooks of Kath Walker and Graeme Elliott and their teams of albatross researchers, who had been visiting Adams Island (in the Auckland Islands) and Antipodes Island since 1991 and 1994 respectively. They had kept records of any snipe nests found and chicks seen, and in many cases had photographed the chicks. From my studies of Snares Island snipe, I knew that the two eggs in a snipe clutch are laid 3 days apart and take about 22 days to hatch. I also had detailed measurements and descriptions of chick growth and plumage development, and so was able to estimate the approximate laying dates of any nests where the hatch date was known, and also for any chicks that had been measured, described or photographed. The resulting graph of the timing of breeding of Antipodes Island snipe produced an even bigger surprise than the August lay dates I had deduced in 1990.

The first Campbell Island snipe caught, in November 1997. Photo by Jeremy Carroll, NZ Birds Online

The first Campbell Island snipe caught, in November 1997. Photo by Jeremy Carroll, NZ Birds Online

Antipodes Island snipe nest. Photo by Mark Fraser, NZ Birds Online

Antipodes Island snipe nest. Photo by Mark Fraser, NZ Birds Online

Antipodes Island snipe not only started breeding earlier in the year than related forms, they then stopped breeding for two and a half months at the height of summer, before resuming again in the last week of January. This gap in breeding from mid-November to late January occurred precisely when most snipe pairs on the Snares Islands and Auckland Islands were breeding. Adams Island is at a similar latitude to Antipodes Island, and the higher slopes (where the albatrosses breed) have similar vegetation. However, 73% of the snipe pairs on Adams Island bred during the 10 weeks when no snipe were breeding on Antipodes Island. Why do Antipodes Island snipe have this bizarre bimodal breeding season, and avoid breeding when other snipe do?
Antipodes Island snipe holding food for its chick. Photo by Mark Fraser, NZ Birds Online

Antipodes Island snipe holding food for its chick. Photo by Mark Fraser, NZ Birds Online

Laying dates of Antipodes Island snipe (above) and Auckland Island snipe. The data shown are the number of clutches estimated to have been commenced per 10-day period. The labels below are months, starting at July. Based on a figure published in Notornis 53(4), 2006, reproduced with permission of Birds New Zealand

Laying dates of Antipodes Island snipe (above) and Auckland Island snipe. The data shown are the number of clutches estimated to have been commenced per 10-day period. The labels below are months, starting at July. Based on a figure published in Notornis 53(4), 2006, reproduced with permission of Birds New Zealand

The most obvious difference in the ecology of the two islands is that one of them (Antipodes Island) has mice. Kath and Graeme also kept notes on how often they saw snipe on the two islands while walking to and within their albatross study areas. Snipe were seen 3.4 times more often on Adams Island than Antipodes Island. We hypothesised that mice on Antipodes Island were disrupting the invertebrate food-web that snipe depend on, but there has not been any opportunity to study how this occurs, nor why the breeding-gap appears to occur year after year without any exceptions. If mice were competing with snipe for food, surely there would be occasional good years for snipe?

Our hope is that mouse eradication on Antipodes Island will lead to higher densities of snipe, and will allow them to breed in summer. Or is there some other explanation for the unusual breeding behaviour of Antipodes Island snipe?

 

Further reading

Barker, D.; Carroll, J.; Edmonds, H.; Fraser, J.; Miskelly, C.M. 2005. Discovery of a previously unknown Coenocorypha snipe in the Campbell Island group, New Zealand subantarctic. Notornis 52: 143-149.

Miskelly, C.M.; Baker, A.J. 2009. Description of a new subspecies of Coenocorypha snipe from subantarctic Campbell Island, New Zealand. Notornis 56: 113-123.

Miskelly, C.M.; Bell, E.A.; Elliott, G.P.; Walker, K.J. 2006. ‘Hakawai’ aerial displaying by three populations of subantarctic snipe (genus Coenocorypha). Notornis 53: 375-381.

Miskelly, C.M.; Fraser, J.R. 2006. Campbell Island snipe (Coenocorypha undescribed sp.) recolonise subantarctic Campbell Island following rat eradication. Notornis 53: 353-359.

Miskelly, C.M.; Walker, K.J.; Elliott, G.P. 2006. Breeding ecology of three subantarctic snipes (genus Coenocorypha). Notornis 53: 361-374.

 

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