Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Brooke (2004) estimated the global population to potentially number over 200,000 individuals.
The population is suspected to be in decline owing to predation by invasive species.
The Grey-backed Storm-petrel has a circumpolar distribution in the subantarctic, breeding on islands from the Falkland Islands (Islas Malvinas) in the south-west Atlantic east to the Chatham Islands (New Zealand). Individuals can winter nearer to the continents, when they are found off the extreme southern coast of Argentina, and south-east Australia and Tasmania (del Hoyo et al. 1992).
This marine species occurs in the cool waters of the subantarctic zone. It is generally found over the edge of the continental shelf and is apparently only pelagic during dispersal. Its diet comprises mainly of immature barnacles and other crustaceans, but also small squid and occasionally small fish. It catches prey mostly by pattering over the surface whilst in flight, but also by dipping and shallow plunging. It has been seen to attend trawlers and occasionally follows ships. Its breeding season starts in October or November, with individuals forming loose colonies on oceanic islands, creating burrows in vegetation or nesting in crevices in rocks (del Hoyo et al. 1992).
This species may be at risk from egg predation by invasive mice, suspected on Antipodes Island (Burger and Gochfeld 1994 in Angel et al. 2009). A number of Grey-backed Storm-petrels are killed each year due to light-induced collisions with boats however, the extent of this seems to be small (Black 2004).
Text account compilers
Ekstrom, J., Butchart, S., Fjagesund, T., Calvert, R., Hermes, C., Martin, R., Miller, E., Stuart, A.
BirdLife International (2019) Species factsheet: Garrodia nereis. Downloaded from http://www.birdlife.org on 23/07/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/07/2019.