Pest species management is causing rapid and signifi cant changes to burrow-nesting petrel populations on sub-Antarctic Macquarie Island. The Weka, Gallirallus australis, was eliminated by 1989 and the Feral Cat, Felis catus, eradicated in 2000. The most abundant burrow nesting petrel species currently, White-headed Petrels, Pterodroma lessonii, Antarctic Prions, Pachypti!.a desolata, and Sooty Shearwaters, Puffinus griseus, have yet to increase in numbers, but are expected to do so in the absence of cats. This study found evidence that Grey Petrels, Procellaria cinerea, began breeding again on the island in 1999, after an absence of over 100 years. Blue Petrels, Halobaena caerulea, and Fairy Prions, Pachyptila turtur, were found to be re-colonising Macquarie Island from offshore stacks after a similar absence. South Georgian Diving-Petrels, Pelecanoides georgicus, were also possibly recolonising the island. Despite the presence of Black Rats, Rattus rattus, most of the bird species discussed are considered capable of population increase. If European Rabbits, Oryctolagus cuniculus, are not elimi nated or maintained in reduced numbers, some petrel populations will never fully recover. Climate change could have a negative impact on burrow-nesting petrels, and is likely to exacerbate the detrimental effects of the remaining pest species on vulnerable indigenous bird species, compounding the need for remedial action against rabbits in particular. Together with predictions that other petrel species will now return to breed, certain terrestrial bird species, alien to the region, may invade Macquarie Island as a consequence of the combination of pest eradication and changing climatic conditions.