Described by Robert Falla in 1946, it is a stocky bird weighing approximately 1,100 grams (39 oz), and is one of the largest of the burrowing petrels.

The only known breeding colonies of the Westland petrel are in New Zealand, in a small area of forest-covered coastal foothills between Barrytown and Punakaiki on the South Island's West Coast.

In 2014, the breeding colony areas suffered extensive damage from landslips and tree fall during the tail-end of Cyclone Ita.

Other significant potential threats to the breeding colonies are predation by feral pigs and vagrant dogs from nearby settlements.

[4] The Westland petrel was identified in 1945 after the students of Barrytown School wrote to Falla, as he was then the director of the Canterbury Museum.

Initially he considered that the West Coast birds were a subspecies of the black petrel (Procellaria parkinsoni), but it was soon classified as a separate species.

[4]Moulting occurs in the Westland petrel in their non-breeding season between October and February, during migration to South America.

[7] In the non-breeding season, the birds migrate east to waters off South America and feed in the Humboldt Current.

[1] Their large size and aggressive behaviour have helped to ensure that they can resist predators that would attack smaller species.

[10] Westland petrel are winter breeders, arriving at their breeding grounds annually in late March or early April to prepare their burrows for nesting.

[22] Westland petrels can forage during both day and night, preying primarily on fish, some squid, and less commonly on crustaceans.

[23] 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.

This means that the loss of a breeding colony through landslides, predation or human interference can have severe consequences for the population.

[26] Predation by feral pigs and vagrant dogs are among the top threats to Westland petrels at the breeding colonies.

[27] Burrow-nesting seabirds like the Westland petrel returning to their burrows at night, or leaving them before dawn, can become disoriented by artificial lights and crash land on roads.

In 2009, the Department of Conservation asked residents of Punakaiki to help reduce the occurrences of fledgling birds crash landing in the town by turning off outside lights and closing blinds at night, particularly during misty or stormy weather.

[28] In 2020, the NZ Transport Agency (Waka Kotahi), in what was reported as a nationwide-first, turned off streetlights in Punakaiki between November and January, the period when the fledgling birds leave their burrows and take their first flight.

[29] Shortly after the start of this conservation initiative, Westland petrels were found crash-landed in Greymouth, in larger numbers than reported in previous years.

[32][33] In February 2022, the Grey District Council and the West Coast Regional Council declined an application to mine 5,000 tonnes of ilmenite sands per week, citing environmental concerns, including the potential effects on sensitive waterways and the risks to Westland petrels from vehicle activity and lights associated with the mining project.

This is a significant risk for Westland petrels, as they are known to interact closely with the fishing vessels and forage from fishery waste.

[2] During the fledging season, a team of local conservationists patrol an 8 km (5.0 mi) section State Highway 6 in the Barrytown Flats area that lies beneath the flight path from the breeding colonies, looking for birds that have crash-landed on or near the road.

[35] Every year, a festival is held in Punakaiki to celebrate the return of the petrel to its only known breeding sites, close to the town.

[36] There is an ecotourism business in the area that provides viewing opportunities at the breeding colony located on private land.