have helped to ensure that they can resist predators that would attack smaller species. Westland petrels nest in burrows dug 1 to 2 metres into the hillside, often on a steep slope. There are around 29 colonies of petrel in the breeding territory. Each colony has between 50 to 1000 burrows. Colonies can be located anywhere from above sea level. Westland petrel are winter breeders, arriving at their breeding grounds annually in late March or early April to prepare their burrows for nesting. Colonies are noted to be very vocal around three weeks before nesting, during the time when courtship and mating occur. Petrels can form life time pair-bonds. The female lays a single egg between May and June that hatches two months later, between August and September. Both the male and female taking turns incubating the egg. After hatching, the parents care for the chick for about two weeks. After this time the chick is left alone, but is fed at night. If either parent dies before the chick is nearly ready for fledging, the chick will not survive. Fledging occurs between 120 and 130 days after hatching. Fledging begins in early November, with a peak around 20 November, and finishes in mid-January. In total, chick rearing takes between 177 and 198 days (approximately 6 to 6.5 months). After leaving the nesting sites, fledglings may not return for up to 10 years. Diet and foraging Petrels are nocturnal and hunt at night, preying primarily on fish, some squid, and less commonly on crustaceans. Westland petrels are known to opportunistically scavenge fish from waste discarded by hoki fisheries during their breeding season as it overlaps with the fishing season, switching back to natural foraging at other times. They capture their prey by seizing or diving from the surface, and, less frequently, pursuit plunging. They have been recorded diving to depths of . Their strong vision allows them to spot prey, and recent studies have shown that smell is also important to petrel foraging, specific odours seeming to attract the birds to certain areas. Threats Breeding colony hazards Westland petrels, along with other types of seabird exhibit natal philopatry—they return to their natal colony to breed. This means that the loss of a breeding colony through landslides, predation or human interference can have severe consequences for the population. Storm, landslide and tree fall The breeding colonies are often on steep sites,