Campbell Island

Forest and Bird, Issue 268, 1 May 1993, Page 3

Campbell Island

Alan Tennyson

A SERIES OF recent studies organised by the Department of Conservation have shown a continuing decline in a number of bird and marine mammal colonies on Campbell Island. New Zealand’s southernmost subantarctic island is a critical breeding island for many seabirds and marine mammals because it is surrounded by a vast expanse of ocean that is a very rich source of food. More than 95 percent of the world’s southern royal albatrosses, for example, breed on Campbell. Despite its remoteness, the 11,000-hectare island has also suffered greatly from human impact. Thanks to conservationists, however, there is optimism that one day much of its former glory may return. The effects of removing browsing mammals is already apparent with the spectacular and palatable megaherb species rapidly recolonising parts of the island. Cattle were removed in 1984 and the last sheep was shot in November 1991. Norway rats and cats are still widespread and they have wiped out all the smaller ground-dwelling birds, such as pipits and storm petrels, and many insects. Fortunately for many of these species, small offshore stacks, such as Dent Island, act as predator-free refuges. The Campbell Island

teal now survives in the wild only on Dent Island, but a mainland captive breeding programme is being attempted (see Forest & Bird May 1991). Rapidly developing eradication techniques provide hope that one day these mammalian predators will be removed from the main island allowing some of the native species to recolonise or be reintroduced. Some of the more difficult management problems involve marine changes which are still little understood. The spectacular rockhopper penguin colonies numbering almost a million pairs in the 1940s have dwindled to 50,000 pairs at the latest count, and elephant seals have decreased by over 95 percent during this period. Both grey-headed and blackbrowed mollymawks (small albatrosses) have also decreased, with the grey-heads suffering substantially more than the black-brows. Populations of all these species and yellow-eyed penguins appear to be still decreasing and while water temperature change has been suggested as the cause of these declines, other factors including the drowning of mollymawks and royal albatrosses on longlines, and the depletion of fish stocks such as southern blue whiting around the islands may also be causal factors.