Mottled Petrel Pterodroma inexpectata


Justification of Red List Category
This poorly known seabird breeds on only a few moderately small islands; on a number of these there are introduced predators and the population is therefore thought to be declining. It is consequently classified as Near Threatened.

Population justification
Brooke (2004) estimated that the population was likely greater than 1,500,000 individuals.

Trend justification
There are no data, but the species is thought to be declining due to the depredations of introduced predators on the breeding grounds.

Distribution and population

Pterodroma inexpectata is endemic to New Zealand. It breeds on islands off Fiordland, the Solander Islands, Foveaux Strait islands, islands around Stewart Island (including Titi islands, Codfish, Big South Cape Islands, and islets in Port Pegasus) and the Snares Islands (Marchant and Higgins 1990, Heather and Robertson 1997). It once bred throughout the North and South Islands, and possibly the Chatham, Bounty, Antipodes and Auckland Islands (Marchant and Higgins 1990, Heather and Robertson 1997). There are c.10,000+ pairs on each of Big South Cape and Main Islands (Heather and Robertson 1997), and the Codfish population was estimated at 300,000-400,000 pairs in 1996 (Taylor 2000). It migrates to the north Pacific as far as the northern Gulf of Alaska and the southern half of the Bering Sea and in summer can range as far south as the pack ice (Ainley and Manolis 1979, Marchant and Higgins 1990, Heather and Robertson 1997, Ogi et al. 1999). 


It breeds in burrows on remote offshore islands and otherwise ranges widely at sea.


This species seems to be vulnerable to changing ocean temperatures, with relatively large numbers were observed washed up during the El Nino event in 1997 in both New Zealand and Alaska (Taylor 2004). Invasive species also represent a threat; the Weka Gallirallus australis, has been introduced to several colonies, and has caused significant losses on Codfish Island (Taylor 2000). House Rat Rattus rattus is present on Big South Cape Island, and may have a severe impact on breeding success. Some populations are on islands that are regularly harvested for Sooty Shearwater Puffinus griseus chicks, but there is little evidence for this having an effect on the species (Heather and Robertson 1997, Taylor 2000).

Conservation actions

Conservation Actions Underway
None is known.

Conservation Actions Proposed
Monitor suitable colonies to assess population trends. Complete pest plan to prevent and enable rapid responses to new species introductions. Eradicate Weka G. australis from Big Solander Island, and Weka and House Rat R. rattus from Big South Cape Island, on agreement with owners. 


Text account compilers
Stuart, A., Symes, A., Taylor, J., Mahood, S., Martin, R., Fjagesund, T., Hermes, C., McClellan, R., Moreno, R., Morgan, K., O'Brien, A.

Recommended citation
BirdLife International (2022) Species factsheet: Pterodroma inexpectata. Downloaded from http://www.birdlife.org on 10/08/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 10/08/2022.