There are at least eight species of burrowing petrel on Macquarie Island. Each species lay one egg in a burrow underground. Grey petrels breed during winter, whereas the rest breed during the summer months. Birds are typically absent from the island outside their breeding season, except blue petrels which are resident year-round. After the successful eradication of vertebrate pests from Macquarie Island (cats, rats, rabbits and rodents), several species that were restricted to offshore rockstacks are now breeding on the main island. The primary threat to these species on land is predation by skuas and giant petrels, and some species can be impacted by fishing operations at sea.