Grey-faced Petrel (Pterodroma gouldi)

Detailed introduction

The Grey-faced Petrel (scientific name: *Pterodroma gouldi*) has no subspecies. Prior to 1993, the Grey-faced Petrel (*P. gouldi del Hoyo and Collar* 2014) and the Giant-winged Petrel (*Pterodroma macroptera*) were classified as two separate subspecies under the name *Pterodroma macroptera*. In 2014, they were separated into two distinct species.

During the breeding season, the Grey-faced Roundtail Shearling primarily forages in the Tasman Sea or the waters east of New Zealand, near the edge of the continental shelf, or in deeper waters, ranging from thousands of kilometers. During summer molting, they are widely distributed across the Tasman Sea to the Australian coast, with some reaching the Coral Sea.

The Grey-faced Roundtail is nocturnal while at breeding grounds. Unlike other species of the same genus on the southern islands, they are very active in their colonies at night, calling and searching for burrows, as well as moving and sleeping on the shore. On damp nights, shore activity is more pronounced, but they return on windy nights under bright moonlight. A spectacular aerial courtship chase is a characteristic of this species, and breeding grounds can be very noisy during April-May and August. At sea, they fly rapidly to the edge of the continental shelf before beginning to forage. They can travel great distances in search of food, and have been recorded flying to the east coast of Australia while their mates are incubating eggs. After breeding, the Grey-faced Roundtail disperses primarily to the warmer waters of the Northern Tasman Sea or the southern and eastern waters of Australia.

The Grey-faced Round-tailed Shearling has a wide diet, most commonly feeding on squid, but also eating crustaceans and fish. It hunts at night, but often anchors at sea during the day and may prey on other animals. It catches smaller squid alive at the surface, but larger squid are likely eaten when dead animals float to the surface. Studies of the species' diving ability indicate that they primarily forage at depths of 5 meters below the surface, but occasionally dive to depths of up to 20 meters. The nocturnal nature of its prey may be due to the prevalence of bioluminescence, suggesting this is a method of prey location for the bird. It occasionally appears after cetaceans and mixes with other shearlings. Its primary flight calls are high-pitched whistles (whi-her, wik-wik) or low moans (oor-wik). These identical calls are frequently heard on the ground or in burrows.

The Grey-faced Roundtail breeds in northern New Zealand, on islands, and some mainland headlands. These birds begin breeding in the dead of winter, but many chicks don't fully emerge until mid-summer. Some Maori tribes still exercise their right to hunt on the islands, harvesting Grey-faced Roundtail chicks between mid-November and mid-December each year. As predators on many breeding islands are eliminated, the Grey-faced Roundtail will regain its abundance.

The breeding season for the Grey-faced Round-tailed Shearling is roughly from early March to January of the following year. They nest in loose colonies on ridges, slopes, or flat ground on ocean islands, using burrows that can be about 1.5 meters long. A single white egg, measuring 68 x 48 mm, is laid between mid-June and late July. The neatly arranged nest cells are located at the end of a long burrow dug into the soil or vegetation. The egg hatches in August or September, with an incubation period of about 55 days. The chicks develop feathers during the winter, from November to January of the following year, at approximately 118 days old. This species breeds once a year; very few pairs skip the breeding season. Both parents share incubation and chick care. The young birds' plumage is fully developed by late December. Immature chicks begin to return to the colony at age 3 and can breed as early as age 4, but most delay breeding until 8-10 years old.

Invasive mammalian predators are the primary threat to the Grey-faced Roundtail. Cats, Polynesian rats, brown rats, house mice, stoats, and pigs are all thought to cause population decline by raiding nests and reducing reproductive success; cats also prey on adult birds. Eradication efforts have been undertaken to reduce the numbers of cats and Polynesian rats. Removal of each species from breeding islands has resulted in an increase in the Grey-faced Roundtail population (Greene et al., 2015). Cats remain on one breeding island and are distributed across the continent outside the fenced area, while Polynesian rats remain in certain areas of their range. Brown rats and house mice remain on nine and fourteen breeding islands, respectively. The species is still legally fished on some offshore islands in the Bay of Plenty and the Hauraki Gulf; however, efforts have been made to ensure that current harvests are sustainable (Greene et al., 2015).

Listed as Least Concern (LC) in the IUCN Red List of Threatened Species 2018 ver3.1.

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