Grey-backed Storm Petrel
Garrodia nereis
Number Of Mature
Individuals (Regional)
2 000
Regional
Population Trend
Decreasing
2025
Regional Category
Near Threatened
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CONTENTSOverview
Names
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IOC English Name: |
Grey-backed Storm Petrel |
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SA & IOC Scientific Name: |
Garrodia nereis |
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BirdLife International Taxonomy (scientific name): |
Garrodia nereis |
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Order: |
PROCELLARIIFORMES |
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Family: |
Oceanitidae |
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Species name author: |
Gould 1841 |
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Afrikaans: |
Grysrugstormswael |
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Sesotho (South Africa): |
Lefokotsanefefo la mokokotloputswa |
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Sesotho (Lesotho): |
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Siswati: |
|
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Zulu: |
unohhalomhlanompunga |
Current Assessment Status
|
2025 Regional Category [Criteria] |
NTo [A3e; D2] |
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2024 Global Category [Criteria] |
LC (BirdLife International 2018) |
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Population size (Regional) |
Unknown, 2000 breeding adults estimated in 2008 (Ryan and Bester 2008) |
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Population size (Global) |
Unknown (BirdLife International 2018) |
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Distribution size (EOO) (Regional) km2 |
c. 720 (breeding) |
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Distribution size (EOO) (Global) km2 |
78 000 000 (BirdLife International 2018) |
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Distribution size (AOO) (Regional) km2 |
334 (breeding) |
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Generation time |
4.6 years (Bird et al. 2020) |
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Status change reason |
No Change |
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Migrant (in the region) |
Possibly |
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Regional endemic |
No |
Historic Listing Information
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2000 Regional Status |
LC |
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2015 Regional Status |
NT [D2] |
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Status change reason (if applicable) |
Criteria Revision |
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2015 Population size (Regional) |
Unknown |
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2015 Global Status |
LC |
Reason for Inclusion
Reason for Inclusion in the Assessment
The Grey-backed Storm Petrel Garrodia nereis was previously assessed as Near Threatened in the 2015 regional assessment (Madden and Wanless 2015).
Category Justification
Category Justification
The regional population of Grey-backed Storm Petrel breeds on Prince Edward Island and has been confirmed to breed on Marion Island (Nelson Mandela University (NMU) and FitzPatrick Institute of Africa Ornithology (FPIAO), unpubl data), 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). Preston et al. (2019) indicate that the species possibly extirpated from Marion Island due to mice predation. In addition, the species qualifies for Vulnerable (VU) under Criterion A3 due to projected future declines based on expert-assessed extinction horizons due principally to the threat of House Mice Mus musculus on Marion Island (Preston et al. 2019). While there is limited direct evidence of ongoing population decline currently, predictive assessments suggest that the species may experience a significant reduction over the next three generations. The extinction horizon estimates indicate that the species’ population may decline by 43% within this period, exceeding the threshold for VU under A3 (Lee 2025). There is a probability that a rescue effect may occur as the global population is relatively large, hence the Grey-backed Storm Petrel is assessed NTo [A3e, D2].
Population Justification
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 2000 (Ryan and Bester 2008). Grey-backed Storm Petrels have been confirmed breeding on Marion Island (NMU, FPIAO, unpubl data), but the population size remains unknown. Confidence in this regional population estimate is low.
Trend Justification
The global population is thought to be in decline due to predation by invasive species (BirdLife International 2018). Trends on Marion and Prince Edward islands are unknown.
Biology & Ecology
Taxonomy
Grey-backed Storm Petrels are placed in the genus Garrodia, within Oceanitidae (Cibois et al. 2015).
Identification
This small storm petrel measures 20–22 cm and weighs 48–60 g. It resembles Wilson’s Storm Petrel Oceanites oceanicus but is smaller than the White-faced Storm Petrel Pelagodroma marina. Its black, white, and grey coloring gives it a distinctive hooded look. The upperparts are black with a grey wash across the back and wings, and the rump and tail are grey with a black tip. The upper breast is black, while the belly and flanks are white. The underwing is pure white with a bold black leading edge and dark secondaries. Eyes, bill, legs, and feet are blackish (Onley and Scofield 2007).
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 has recently been found breeding on South Africa’s Prince Edward and Marion islands (Cooper and Brooke 1984, NMU, FPIAO, unpubl data). The species is a rare, but possibly under-reported, vagrant to South African waters (Madden and Wanless 2015).
Ecology
The Grey-backed Storm Petrel is generally found over the edge of the continental shelf and is apparently only epipelagic during dispersal. The diet consists mainly of immature barnacles and other crustaceans (e.g. Imber 1981), but also small squid and occasionally small fish (BirdLife International 2018). 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 November, with eggs laid in December and chicks hatching in January. Individuals form loose colonies, creating extremely shallow burrows in vegetation or nesting in crevices in or among rocks (NMU, FPIAO, unpubl data).
Threats & Conservation
Threats
Threats to this species are largely unknown. The population is estimated to be declining due to invasive species on breeding islands (BirdLife International 2018). Predation by mice at Marion Island is a potential threat to adults or chicks. Mortality records attributed to collisions with vessels exist (Black 2005).
Conservation Measures 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.
Conservation Measures Proposed
No conservation actions are currently proposed, as there are no overt threats to this species in the region. Eradication of mice at Marion Island will be beneficial to the species.
Research Priorities and Questions
- Very little 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, would be useful for modelling population trends.
- Levels of connectivity and meta-population dynamics between any Prince Edward Island colonies and elsewhere should be assessed. Movements of this species during and outside the breeding season are also unknown, including the geographical range of juveniles.
- The potential effects of invasive house mice on their breeding success needs to be established.
Contributors & References
Assessor/s
Stefan Schoombie
Reviewer/s
Maëlle Connan
References
Bird JP, Martin R, Akçakaya HR, Gilroy J, Burfield IJ, Garnett ST, Symes A, Taylor J, Şekercioğlu ÇH, Butchart SH. 2020. Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology 34:1252–1261. DOI: 10.1111/cobi.13486.
BirdLife International. 2018. Garrodia nereis. The IUCN Red List of Threatened Species 2018: e.T22729148A132660152. Available: https://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T22729148A132660152.en. [Accessed on 18 August 2023].
Black A. 2005. Light induced seabird mortality on vessels operating in the Southern Ocean: incidents and mitigation measures. Antarctic Science 17: 67–68.
Brooke MD. 2004. Albatrosses and Petrels Across the World (Bird Families of the World). Oxford, United Kingdom: Oxford University Press.
Cibois A, Thibault J, LeCroy M, Bretagnolle V. 2015. Molecular analysis of a storm petrel specimen from the Marquesas Islands, with comments on specimens of Fregetta lineata and F. guttata. British Ornithologists’ Club 135(3): 240–246.
Cooper J, Brooke MD. 1984. Breeding status of burrowing petrels at Prince Edward Island. Unpublished report.
Imber MJ. 1981. Diets of stormpetrels Pelagodroma and Garrodia and of prions Pachyptila (Procellariiformes). In Cooper J (ed), Proceedings of the Symposium on Birds of the Sea and Shore, 1979. Cape Town: African Seabird Group. pp 63–88.
Lee ATK. 2025. The application of IUCN Regional Red List Criteria to the species of South Africa’s Prince Edward Islands. Unpublished report. Johannesburg: BirdLife South Africa.
Madden CF, Wanless RM. 2015. Grey-backed Storm Petrel. In: Taylor MR, Peacock F, Wanless RM (eds), The Eskom Red Data Book of Birds of South Africa, Lesotho and Swaziland. Johannesburg: BirdLife South Africa. pp 344–345.
Onley D, Scofield P. 2007. Albatrosses, Petrels and Shearwaters of the World. London, United Kingdom: A&C Black.
Preston GR, Dilley BJ, Cooper J, Beaumont J, Chauke LF, Chown, SL, Devanunthan N, Dopolo M, Fikizolo L, Heine J, Henderson S, Jacobs CA, Johnson F, Kelly J, Makhado AB, Marais C, Maroga J, Mayekiso M, McClelland G, Mphepya J, Muir D, Ngcaba N, Ngcobo N, Parkes JB, Paulsen F, Schoombie S, Springer K, Stringer C, Valentine H, Wanless RM, Ryan PG. 2019. South Africa works towards eradicating introduced house mice form the sub-Antarctic Marion Island: the largest island yet attempted for mice. In: Veitch CR, Clout MN, Martin AR, Russell JC, West CJ (eds), Island Invasives: Scaling up to Meet the Challenge. Occasional Paper of the IUCN Species Survival Commission; Vol. 62 pp 40–46. IUCN. https://portals.iucn.org/library/node/48358.
Ryan PG, Bester MN. 2008. Pelagic Predators. In: Chown SL, Froneman PW (eds), The Prince Edward Islands: land-sea interactions in a changing ecosystem. Stellenbosch, South Africa: Sun Media. pp 121–164.
Citation
Schoombie S 2025. Grey-backed Storm Petrel. In: Lee ATK, Rose S, Banda S, Bezeng SB, Maphalala MI, Maphisa DH, Smit-Robinson H (eds), The 2025 Red Data Book of Birds of South Africa, Lesotho and Eswatini. Johannesburg, South Africa: BirdLife South Africa. Available at: https://www.birdlife.org.za/red-list/grey-backed-storm-petrel/
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