Isles Kerguelen harbour an astonishing diversity and abundance of seabirds, with 33 breeding species. We had seen breeding colonies of several of the larger species on Grand Terre, but Mayes provided a taste of what the islands would have been like before their discovery – and the introduction of cats, rats and rabbits in particular. There are hundreds of islands in the archipelago, and those lacking introduced predators (plus the unvegetated highlands of Grand Terre) between them provide breeding sites for 15 species of burrow-nesting petrels, most of which nest on Mayes.
The hut on Mayes is used almost exclusively by bird researchers. Skuas, sheathbills, rockhopper penguins and Kerguelen shags are studied, but almost all the field work is focused on the long-term demographic study of petrels. At present there are hundreds of study burrows monitored for grey petrel, white-headed petrel, blue petrel and thin-billed prion, and all four species plus common diving petrel and Wilson’s storm petrel are also monitored by regular mist-netting (at night) near the hut. Grey petrels are winter breeders and were not present during our visit, but the five other species were all present and breeding. Smaller numbers of white-chinned petrel, great-winged petrel, Kerguelen petrel, Antarctic prion, South Georgian diving petrel, grey-backed storm petrel and black-bellied storm petrel are also known or suspected to breed, leaving only soft-plumaged petrel and fairy prion as local species not known to occur on the island.
The main purpose of our visit was to establish a study colony of common diving petrels – the same species that I study on Mana Island near Wellington. Charly Bost wishes to compare the foraging ecology of these birds with the closely-related South Georgian diving petrel, which breeds in larger numbers on Ile aux Cochons, 6 km away (the next site we will visit). Previous attempts to study common diving petrels on Mayes had been terminated as it was suspected that disturbance was causing some birds to shift breeding sites between seasons. We were hoping to train birds to accept artificial nest boxes installed at nest sites, allowing easy inspection of nest contents. We also hoped that the narrow plastic entrance tunnels would exclude larger petrel species that could otherwise take over the burrow. Charly also wished to attach tiny (2.6 g) GPS logging tags on a few breeding birds, and to recover the tags after the birds returned from a foraging trip at sea.
The birds were mostly on eggs at the time of our visit, and we decided that it would be best for the third team member Aymeric Fromant (and assistants) to install most of the nest boxes on his next visit, when the birds would be feeding chicks (and no adults would be present in the day time). I installed a single box as a demonstration, and we experimented with whether the birds would accept a 62 mm internal diameter pipe inserted in their burrow, and whether this diameter pipe would exclude blue petrels and thin-billed prions.
We searched for burrows at two sites – near the hut and at “Plon-Plon Beach” about 20 min walk away. ‘Plon plon’ is a local nickname for common diving petrel, derived from ‘le petrel plongeur’. The main technique used (as for Mana Island) was to mimic the birds’ calls and to trace any responses to a burrow. This is very effective at night, and I was surprised to find that many birds would also respond in the late afternoon.
By the end of our stay we had 27 marked burrows containing eggs and one with a chick, and had deployed six tail- or back-mounted GPS tags (and retrieved three). We also deployed three leg-band-mounted geo-logger tags as a trial. I also assisted Aymeric with monitoring blue petrel breeding success, checking about 60 study burrows for newly-hatched chicks.
Te Papa curator of vertebrates Dr Colin Miskelly’s participation in seabird research programmes on the French subantarctic island groups of Crozet and Kerguelen was at the invitation of Dr Charly Bost of the CEBC laboratory (Chizé) of CNRS (Centre National de la Recherché Scientifique), France, and was supported by the Institut Polar Français Paul Emile Victor (IPEV) and Te Papa.
Previous blogs in this series
A week on Ile Mayes, Iles Kerguelen
Subsequent blogs in this series