Isolated at the bottom of the globe’s largest ocean and bathed by rich ocean currents, it is no surprise that New Zealand is a world centre of seabird diversity. We are a hub for albatrosses, the world’s largest seabirds, with 14 out of all 24 known global species breeding in our waters.

In this blog, Auckland Museum's Curator, Land Vertebrates Matt Rayner takes us on a journey beyond the northern-most tip of Aotearoa to Manawatāwhi (Three Kings Islands) to uncover the mystery of the islands' albatrosses. 

These majestic giants spend up to 85 percent of their lives far beyond land out on the open ocean, gliding effortlessly in search of food. Yet tragically, most albatross species (19 out of 24) are threatened with extinction, largely as a result of being killed in interactions with fishing boats or eaten at their breeding sites by introduced mammalian predators. Albatrosses breed on remote oceanic islands, as far from humans as possible. Despite this isolation, most breeding sites are known, and many are monitored to track the birds’ numbers, making it unusual in New Zealand, or globally, that a new albatross population should be discovered and remain unstudied.

In December 1983, such an event happened when Anthony Wright, then Curator of Botany at Auckland War Memorial Museum, ventured ashore on a rock stack that forms part of a chain of islands north of New Zealand known as Manawatāwhi (Three Kings Islands). The rock, named Rosemary after the yacht that had transported Auckland Museum field parties to Manawatāwhi in the 1940s and 50s, is clothed in unique salt tolerant vegetation that Wright was keen to document at the time. It was with some dismay that Wright, possessing a self-confessed bird phobia, was distracted from his botanising by a “strident, duck-like calling” near the summit. Upon investigation he discovered six very large seabirds occupying nests, and took photographs and made detailed observations and sketches. Two years later, others were able to land on Rosemary Rock and collect bill measurements. New Zealand’s bird experts drew into a huddle and concluded that the birds were most likely Buller’s albatross.

Image credit: Featured in the Journal of the New Zealand Ornithological Society Notornis (31) (Wright 1984)

The Buller’s albatross (Thalassarche bullerii) is named after famed bird collector, researcher, and enthusiast, Sir Walter Buller. Quirkily, in New Zealand the species is more commonly known as Buller’s mollymawk. The term mollymawk comes from a 17th century Dutch term mallemok, which translates as foolish (mal) gull (mok). Mollymawks are a group of medium-sized albatrosses of which Aotearoa has an abundance, only two of the world’s nine mollymawk species do not breed here. The Buller’s mollymawk is one of New Zealand’s more numerous species, particularly in its southern waters as their breeding colonies are found on the Chatham and New Zealand sub-Antarctic islands.

Finding a small colony of this predominantly “southern” mollymawk at the top of the North Island and over 1000 kilometres from any other breeding site, was puzzling to say the least. Particularly, which of the major albatross populations were these birds were related to? In the 1980s, it was recognised that not all Buller’s mollymawks were alike.  Birds from the Chatham Islands can be separated from their southern counterparts by differences in bill size, plumage colouration and breeding timetable. Recent genetic analyses have also supported this split, showing Chatham and sub-Antarctic populations are genetically distinct. As a result, they have both been recognised as distinct subspecies: Northern Buller’s mollymawk (Thalassarche bulleri platei) and Southern Buller’s mollymawk (Thalasarrche bulleri bulleri).  Scientists use the term subspecies when they consider populations are different enough to have branched off biologically (i.e., colour, timing of breeding, different DNA), but are similar enough that they could still interbreed with each other if they had the opportunity. However, although albatrosses travel vast distances, they are very much homebodies when it comes to their breeding sites, so interbreeding is unlikely.  

Image credit: Buller’s mollymawk in flight. Edin Whitehead

All of this adds uncertainty to exactly what the Buller’s mollymawks of Rosemary Rock are.  Are they Northern or Southern subspecies, or something different? Such questions are where the rubber hits the road in terms of the relationship between taxonomy (the science of describing and naming biodiversity) and conservation biology (the science of protecting that diversity). Conservation funding and effort is typically based on population size and change of known and described species. If the albatrosses of Rosemary Rock were found to be related to large populations further south, then they would be of lower conservation priority.  However, a tiny population of genetically distinct albatrosses, restricted to one rock stack, would immediately be considered of high conservation concern, possibly even critically endangered.  

Fast forward 37 years to 2020 and we still don’t have that vital information for the Rosemary Rock birds. While this might seem surprising, it is not an unusual situation in our small nation, where important wildlife questions are often left unanswered due to a small pool of researchers, an even smaller pool of funding, and, in this case, the remoteness of the birds in question. However, over the course of several years, Auckland Museum and mana whenua of Manawatāwhi, Ngāti Kuri, had been working on a plan to fill in the blanks. This, of course, would require getting back onto Rosemary Rock, not a simple undertaking. Manawatāwhi lies on an undersea submarine plateau known as the King Bank, 60 kilometres north of Te Rerenga Wairua (Cape Rēinga) at the intersection of the Tasman Sea and South Pacific Ocean. The group is made up of 13 islands and a number of rock stacks, none of which have beaches or easy landing sites. Rosemary Rock is in the Western chain of islands known as the Princes Group. Windswept and completely exposed to Southern Ocean swells, this 50-metre-high lump of basalt, bounded by cliffs, presents a serious challenge to land on, even for experience field researchers.

Image credit: Rosemary Rock, Manawatāwhi​. Jenn Carol

To make this trip, our plan was to target the best possible late-summer weather, a window with light winds and low swells, and visit the island in a single day using a high-speed boat. Outwardly simple, it took two years for these conditions to align. On 27 February 2020, following a pre-dawn karakia, our team (Trenton Neho and Thomas Dvniz (Ngāti Kuri), Kevin Parker (Parker Conservation), Jennifer Carol (Auckland Museum photographer), and myself (Auckland Museum Curator, Land Vertebrates) departed Houhora before the sun was in the sky for a four-hour seaward dash to Manawatāwhi.  

Weather conditions were excellent, so we arrived at the Princes Islands group mid-morning, circling Rosemary Rock to scope out best place to land. A larger-than-forecast swell and strong currents meant we were forced to wait until the turn of the tide for calmer landing conditions. Even with this precaution, stepping off the boat was not going to be possible; we were going to have to swim for it. An hour later, with slack tide conditions we made our move: a short 20 metre swim in life jackets, wetsuits and booties to a wave platform, timing the two-metre swell surge and scrambling ashore. Our gear, secure in a waterproof barrel, had to be hauled up on to the rock using a long rope. A climb up a steep rock face led to a small ledge where we could get dry and organised.

Image credit: Departing Houhora. Jenn Carol

Next was finding our way to the top of the rock, which took us half an hour, during which our excitement increased as we observed at least three Buller's mollymawks flying overhead. We found individual birds and pairs of birds all along the shaded southerly side of the Rock on steep bluffs and cliff edges. Albatrosses, like many of New Zealand’s seabirds, have bred for millennia on islands lacking mammalian predators, and as a result don’t get scared when approached. This lack of fear makes birds naïve when it comes to humans, but they still have a dangerous bill they aren’t afraid to use.

Image credit: Kevin Parker, Parker Conservation

Over the next four hours we were able to capture three adult mollymawks. The birds were impossibly photogenic with a light-grey head, neck and throat, black across the wings and an amazing black bill with yellow on the top and bottom. We also found three nest sites containing large, fluffy chicks. Mollymawks only lay one egg and their single chick is left alone in the nest, sometime for weeks at a time, in between visits from mum and dad. This is not a problem as the chick’s fluffy coat keeps it warm and they are capable of projectile vomiting a noxious stream of fishy stomach oil in self-defence. Despite the hazards of biting bills and projectile vomiting we collected blood samples, measurements and photos from all the birds handled. The top of the rock also made a magnificent vantage point for appreciating the amazing marine life of Manawatāwhi. We sighted huge schools of trevally (araara) and kingfish (haku), at least three sharks and a group of five sunfish.

Image credit: Kevin Parker, Parker Conservation

And then, after a frantic day’s work, we made our exit, climbing back down the rock, executing a well-timed dive and swimming back to the boat for the long journey back to Houhora, exhausted but extremely satisfied.

The next phase of this work on Buller’s mollymawk will move to the lab, where DNA from the collected blood samples will be sequenced and compared with DNA from both subspecies on the Chatham and sub-Antarctic Islands. These results will, finally, provide an answer to the near 40-year-old question of the whakapapa of the Mollymawks of Rosemary Rock. 

Image credit: Projectile vomiting chicks on their nests. Kevin Parker, Parker Conservation

Blog The mystery of Manawatāwhi mollymawks: a history and field report by Auckland Museum Curator, Land Vertebrates Matt Rayner.

Published 7 May, 2020.