Fairy prions are small burrow-nesting seabirds that breed in large colonies on many islands around New Zealand. The largest colony (of about 1.8 million pairs) is on Takapourewa / Stephens Island in the western approaches to Cook Strait. As part of a project to restore the ecology of Mana Island (off the Wellington west coast), the Friends of Mana Island are leading a project to increase the size of the small population of fairy prions that established following the translocation of 240 chicks from Takapourewa in 2002-04.
As described in a previous blog, 100 healthy chicks were removed from burrows on Takapourewa and flown by helicopter to Mana Island on 22 January. This blog describes what happened to the birds after their arrival.
Preparation on Mana Island had begun months earlier, with the construction and installation of 100 artificial burrows. These provide a safe environment for the chicks during their short stay on the island, plus potential breeding burrows for any birds that return to Mana Island as adults in 3-4 year’s time.
The new arrivals were welcomed by Ngati Toa, who acknowledged the taonga accompanied across Cook Strait by the Ngati Koata members of the collecting team. One chick was removed from its carry box to show the assembled crowd. The remaining chicks were kept in the shade, then each was given a drink of water before being placed in its new home (one chick per burrow).
Fairy prions are members of the petrel family, most of which nest in burrows and visit their breeding colonies at night. Other well-known members of the family include the sooty shearwater (the chicks of which are harvested as muttonbirds), and the fluttering shearwater, which often feeds in flocks in the inner Hauraki Gulf, Wellington Harbour and the Marlborough Sounds. All petrels lay a single egg per breeding attempt, and both parents feed their chick semi-digested seafood by regurgitation. The Mana Island project simulates this by feeding the chicks ‘sardine smoothies’ every day via a large syringe and a soft plastic tube that is slipped down the chicks’ throats.
The growth and development of each chick is monitored by recording the extent of down loss and measuring their weight and wing-length each day. Their weight is used to determine the amount of food they are to be given, and whether any birds require a second feed later the same day.
All petrel chicks are independent of their parents as soon as they leave the breeding colony, meaning that translocated chicks do not require any artificial feeding once they complete their feather development and fly out to sea. We used the wing-length of each chick on Takapourewa to estimate how close it was from being ready to fly out to sea, to see if it fell within our selection criteria. The chicks selected for translocation were all estimated to be 2-10 days from fledging (the term used for a chick taking its first flight). Petrel chicks fly out to sea as soon as they get airborne for the first time, and do not return to land until they reach breeding age.
The first chicks departed from Mana Island on the night of 24 January, with more departing each night until the last one left on the night of 2 February. All 100 chicks survived until fledging, continuing the remarkable 100% survival record for fairy prion chicks translocated to Mana Island achieved in 2002-04.
The success of the project won’t be known until the chicks return to Mana Island 3 or 4 years from now. Based on previous studies, we expect about a quarter of these 100 chicks to survive to breeding age, with about 14 returning to Mana Island, and the balance returning to the source colony on Takapourewa.
A large number of people and organisations have contributed to the project. I acknowledge the approval and support received from the Department of Conservation, Ngati Koata and Ngati Toa. The Friends of Mana Island organised the project, including sourcing funding from sponsors OMV, and organising the teams of volunteer feeders under the expert guidance of contractor Helen Gummer. I thank David Cornick for providing images of the first feeding team in action, and all the members of the bird collection team and the volunteer feeders for the long hours that they put in to ensuring that the 100 chicks were found, selected and fledged in good condition.