2011 was a grim year for New Zealand seabirds. They suffered the triple-whammy of nuclear-fallout from the crippled Fukushima Daiichi power plant affecting the North Pacific non-breeding grounds of at least four species, a severe winter storm that killed up to half a million prions, then the Rena oil spill believed to have killed several thousand birds. Compared to the scale of these disasters, attempts to restore seabird populations appear almost futile.
For the past two decades, New Zealand conservationists have been developing techniques for restoring burrow-nesting petrels (including shearwaters and prions) to sites safe from predators. This required overcoming the birds’ strong homing instincts by translocating then hand-feeding young chicks until they completed their feather development and flew out to sea. This method has now been tried on more than ten species of petrels, but progress is glacially slow. All petrel species lay only a single egg per year, and many do not start breeding (or even return to land) until they are four or more years old.
Mana Island, off the Wellington west coast, has been the single site where the greatest effort has been made to restore burrow-nesting petrels. Between 1997 and 2008, over 700 chicks of three species were translocated to the island, and cared for by teams of contractors and volunteers organised by the Department of Conservation and the Friends of Mana Island (a community conservation group). The younger birds are still returning, but over 60 have been recorded back so far.
All three species are now nesting on the island, with increasing numbers of chicks being recorded each year. During the 2011/12 breeding season, 19 chicks are known to have survived to fledging – 8 common diving petrels, 7 fluttering shearwaters and 4 fairy prions. Other chicks are likely to have been produced in undetected or unmonitored burrows (some of the latter are located at inaccessible cliff sites).
In addition to the translocated chicks that returned as adults, a few unmarked birds of each species have been attracted by loudspeakers broadcasting petrel calls each night, and perhaps also by the birds that have returned to the island.
Restoring seabirds takes time and requires a lot of effort. Understanding how to proceed, at what cost, and the likely outcomes, is essential as we consider how to offset the impacts of disasters caused directly or indirectly by humans.