Rationale
(Changed due to Application of criteria)
The regional population of Grey-backed Storm Petrel Garrodia nereis breeds on Prince Edward Island and is suspected to breed on Marion Island, thus satisfying the criterion for classification as Vulnerable under D2 (population limited to a small number of locations, which makes it vulnerable to the effects of human activities or stochastic events. However, it was felt that it is unlikely that the species will become severely threatened within one to two generations and as a result, it is assessed as regionally Near Threatened.
Distribution
Grey-backed Storm Petrels have a circumpolar distribution in the Subantarctic, breeding on oceanic islands including South Georgia, Gough Island, Crozet Islands, Kerguelen Islands, Auckland Islands, Antipodes Island and Chatham Islands (Onley and Scofield 2007). This species is uncommon in the Subantarctic and Antarctic region, remaining in the Southern Ocean year-round and rarely moving north of the Subtropical Convergence (Ryan and Bester 2008). The species' movements are largely unknown and it may be largely sedentary (Onley and Scofield 2007). Breeding is suspected on the Falklands, Stewart Islands and in southern Chile (Onley and Scofield 2007), and on South Africa's Prince Edward and Marion islands (Barnes and Huyser 1998). The species is a rare, but possibly under-reported, vagrant to South African waters.
Population
The global population is estimated at 200 000 mature individuals (Brooke 2004). This species breeds on Prince Edward Island (Cooper and Brooke 1984) where breeding adults are estimated at 2 000 (Ryan and Bester 2008). Barnes and Huyser (1998) suspect that breeding also occurs on Marion Island but give no estimate of the number of breeding pairs. Confidence in this regional population estimate is low.
Population trend
The global population is thought to be in decline due to predation by invasive species (BirdLife International 2014). Trends on Marion and Prince Edward islands are unknown.
Threats
Threats to this species are largely unknown. The population is estimated to be declining due to invasive species on breeding islands (BirdLife International 2014). Mortality records attributed to collisions with vessels exist (Black 2005).
Conservation
Underway
None specific to this species, but various generic conservation measures are in place at its breeding islands. The Prince Edward Islands are listed as a Ramsar Wetland of International Importance, and as a Special Nature Reserve under the Environment Conservation Act (No 73 of 1989) and managed under the Prince Edward Islands Management Plan 1996. The Prince Edward Islands Marine Protected Area was proclaimed in 2013.
Proposed
No conservation actions are currently proposed, as there are no overt threats to this species in the region. Predation by mice is a potential threat that should be addressed.
Research
* Potential impacts of mouse predation on chicks of this species at Marion Island should be investigated.
* Information is required on population numbers and trends on Marion and Prince Edward islands.
* Virtually nothing is known about many basic demographic parameters for this species at the Prince Edward Islands. Knowledge of breeding success, recruitment parameters, longevity, breeding frequency, sex-based differences in parental investment, age/sex structure, etc. would be useful for modelling population trends; currently all this information would have to be inferred from other areas or sister taxa.
* Movements of the Kerguelen Petrel during and outside the breeding season are unknown, including the geographical range of juveniles.
