Whakau (Māori name) or Red Mercury Island (225 ha) (named by Captain James Cook in 1769 because of its reddish coloured cliffs) lies off the east coast of the Coromandel Peninsula, approximately 30 km from Whitianga. It is the second largest of the seven Mercury Group Islands, and is surrounded by boulder beaches, steep coastal cliffs and often rugged seas which offer geological barriers that help confine and protect many enigmatic and threatened native species.
The island is a protected Department of Conservation Reserve, with access and landing restricted to DOC-permitted parties only. As a result, the opportunity to venture ashore and stay on the island for 7 days in early 2013 was considered a real privilege for our small group of conservationists.
Formed sometime in the Pliocene and/ or lower Pleistocene, as part of the Whakau Volcanics (Hayward & Moore 1971), Red Mercury Island’s history is long yet relatively poorly known. Studies in the late 1960’s touched on the island’s geology, and later in the early 1970’s the Auckland University Field Club mounted expeditions to the island to investigate its archaeological history and ecology; describing the vegetation, invertebrate fauna, reptile and bird assemblages, marine biology and undertook studies on introduced rodents (e.g. kiore, Rattus exulans) (McCallum 1983). Following the important findings of the late Tony Whitaker in 1973, who reported significant adverse effects on island lizard populations (including other fauna) as a result of rodents (Whitaker 1973), a series of mammalian eradication programmes began in the late 1980’s, and included the eradication of kiore from Red Mercury Island in 1992. However, since then very little work has been undertaken on the island, and visitations have been limited to DOC staff, scientists and few volunteers involved translocations and post-release monitoring of tuatara (Sphenodon punctatus) and Mercury Island tusked weta (Motuweta isolata).
The island is also home to a range of other interesting native species, including:
Over the last 22 years, the island’s vegetation and fauna have recovered well (with a little help via species reintroductions); enough so that some of the island’s reptile and bird populations are approaching carrying capacity and have become viable for harvest, providing opportunities for island restoration groups to collect founder individuals and start new island populations elsewhere. One such group, the Motuora Restoration Society (MRS), are doing just that and are a third of the way through a programme to restore a population of Pycroft’s petrels (Pterodroma pycrofti) on Motuora Island in the Hauraki Gulf.
Pycroft’s petrel translocation
Pycroft’s petrel is a small gadfly petrel endemic to New Zealand that only breeds on several islands in the northern North Island. Red Mercury Island is considered the species stronghold for the Pycroft’s petrel with an estimated population of between 5,000 and 10,000 breeding pairs as of 2009 (G. Taylor & M. Rayner, unpub. data.), from a total breeding population of 30,000-40,000 individuals (Birdlife International 2013).
Six enthusiastic volunteers/ researchers, including myself, visited the island in March 2013 to complete a survey of the Pycroft’s petrel population, at the three largest colonies (e.g. Base camp, Von Luckner’s Cove, and Roly Poly Bay), in order to gauge the number of birds potentially available for the transfer to Motuora Island. The survey involved thorough searches of every accessible petrel burrow within these colonies and the collection of information on the development stage of any chicks found. But first…we had to deal with a rough boulder beach landing, setting up camp, and tramping out to the colonies.
Prior to entering the colony – which basically consists of a hillside sprinkled with thousands of small burrows and holes in the ground, and overtopped by vegetation and occasional giant boulders – each team gathered a set of burrow-maintenance equipment and set out tip-toeing through a fragile landscape reminiscent of a mature gouda with an equally pungent smell. At each and every burrow we encountered, we would have to drop to the ground and delve our arm into the deep dark crevice in the hope that something warm and fuzzy was home to greet our prying fingers. An outcome of this kind was highly rewarding as there are probably fewer things cuter than a young, fluffy seabird chick…..
…but what they don’t tell you is what other kind of surprises lurk in the depths of seabird burrows! Deceased, maggot ridden bird carcasses, rotten eggs that explode at the slightest touch due to the build-up of gasses and shower your arm with putrid goo, and if you were to be so lucky, an up-close and personal greeting from one of the worlds meanest looking insects…Motuweta isolata!!!
Whenever a burrow was found to be occupied, we gently manoeuvred the bird out towards the entrance and removed it from the burrow to collect morphometric measurements and record the age of the bird. Knowing the age of the birds is crucial in order to carry out a successful translocation. This is because you can’t simply collect seabirds, transfer them to a burrow on another island and expect them to remain and breed at the release site; as is the case with most terrestrial bird transfers. Seabirds require a lot more effort, and need to be anchored to their colonial breeding sites before the chicks leave their burrows and head out onto the open ocean for the first years of their lives. This anchoring phenomenon is often carried out as the chicks begin to grow their adult plumage and begin venturing a short distance out of their burrow entrances each night, possibly as a means of familiarising themselves with both the land- and sky-scape.
Therefore, it is important to collect the chicks before they begin to anchor themselves at their natal burrows and translocate them to new burrows at the translocation site (Motuora Island in this case).
Occasionally, burrows get damaged as a result of walking on the soft friable soil, and repairs are needed to ensure that the burrows remain dark, watertight, and sturdy enough to avoid the roof collapsing in on the chick at a later stage. In some instances, the burrows can be repaired by reconstructing a new ‘roof’ using sticks, branches, rocks and leaf litter, but on other occasions, something more drastic is required. The photographs below show John and Vince installing an artificial observation burrow, which consists of a hard plastic box (green)to form the burrow chamber and a section of flexible pipe to form the new burrow. These observation burrows, as the name suggests, have a specially designed lid that can be opened to reveal the chick within the burrow chamber. This is very handy for monitoring the growth and condition of chicks as it limits the amount of disturbance and damage to a burrow during the monitoring programme…well at least once the burrow has been installed :s
When installing artificial burrows it is absolutely crucial that the position and orientation of the burrow entrance is not altered in any way. This is because the adult birds rely heavily on landscape features and cues to identify their particular burrow entrance from the thousands of holes scattered throughout the colony. Any slight alteration to the position or orientation of the entrance could prevent an adult bird from identifying its own burrow and could result in a chick starving to death.
After checking each burrow, the entrance was marked to indicate that the burrow had been ‘serviced’ and GPS’d for aerial mapping and burrow-density estimate purposes.
After a day of burrow inspections, we all looked forward to the peaceful walk back to camp for a cuppa and a shower with the most spectacular view.
Seventy Pycroft’s petrel chicks were transferred from Red Mercury to Motuora Island on 12 March 2013. This represented the first transfer of three to be undertaken over a 3- year period, as part of a project initiated by the Motuora Restoration Society (MRS) and supported by the Department of Conservation (DOC). The translocation of Pycroft’s petrels to Motuora has three main objectives, the first being to increase the long term security of the species, which is considered an “At Risk – Recovering” species (Miskelly et al. 2008). The second and third objectives include enhancing the ecological restoration of Motuora Island and promoting the public awareness of seabird conservation issues in the region.
Three to four weeks after being transferred to Motuora Island, most of the birds had fledged; taking to the open ocean where they will spend the first 2-3 years of their lives, before hopefully returning to Motuora to breed. Two further transfers of up to 100 chicks will be undertaken in March 2014 and 2015, and a fourth transfer may be considered if required. To read more about the post-translocation activities (e.g. chick feeding and fledging) go to the Motuora Restoration Society website by clicking here.
Thanks to John Stewart and Kay Milton for organising an unforgettable trip, and to the rest of the team for all the fun and adventures!
This post is dedicated to the late Vince Waanders, who tragically passed away five months after joining the trip to Red Mercury Island. Vince was an integral part of the team, offering his experience and wealth of knowledge on seabirds to the rest of us. Vince was an early riser, and took it upon himself to always make sure that the camp was stocked and running smoothly, and that the welfare of the birds throughout the translocation process was the number one priority. He was a genuine kiwi bloke, with self-less personality and a giant heart. I’m glad I had the opportunity to meet him and I thank him for a very memorable fishing trip 🙂 R.I.P. Vince.