Black-bellied Storm Petrel
Fregetta tropica
Number Of Mature
Individuals (Regional)
10 000
Regional
Population Trend
Decreasing
2025
Regional Category
Near Threatened
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CONTENTSOverview
Names
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IOC English Name: |
Black-bellied Storm Petrel |
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SA & IOC Scientific Name: |
Fregetta tropica |
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BirdLife International Taxonomy (scientific name): |
Fregetta tropica |
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Order: |
PROCELLARIIFORMES |
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Family: |
Oceanitidae |
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Species name author: |
Gould 1844 |
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Afrikaans: |
Swartpensstormswael |
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Sesotho (South Africa): |
Lefokotsanefefo la mpantsho |
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Sesotho (Lesotho): |
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Siswati: |
|
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Zulu: |
Unohhalosisusimnyama |
Current Assessment Status
|
2025 Regional Category [Criteria] |
NT° [A3e; D2] |
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2024 Global Category [Criteria] |
LC (BirdLife International 2018) |
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Population size (Regional) |
10 000 breeding adults (Ryan and Bester 2008) |
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Population size (Global) |
Unknown |
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Distribution size (EOO) (Regional) km2 |
Unknown |
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Distribution size (EOO) (Global) km2 |
21 200 000 (breeding/resident) |
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Distribution size (AOO) (Regional) km2 |
44 (confirmed breeding) |
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Generation time |
5.1 years (Bird et al. 2020) |
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Status change reason |
No Change |
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Migrant (in the region) |
Native and breeding visitor |
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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) |
Application of criteria |
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2015 Population size (Regional) |
10 000 breeding adults (Ryan and Bester 2008) (<2500 in previous RDB was likely an error) |
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2015 Global Status |
LC |
Reason for Inclusion
Reason for Inclusion in the Assessment
The Black-bellied Storm-petrel Fregetta tropica was regionally assessed in 2015 as Near Threatened (Hagen 2015). Global and regional population estimates are based on dated data, complicating application of the regional filter. A cautionary approach was adopted, and the species was assessed.
Category Justification
Category Justification
The regional population of Black-bellied Storm-petrel satisfies the criterion for Vulnerable under D2, due to mice predation. This species also 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 44% within this period, exceeding the threshold for VU under A3 (Lee 2025) Since a Regional Rescue Effect is applicable given the pelagic nature of the species, plus a non-threatened global population, the Category is modified to: NTo [A3e; D2].
Population Justification
There is no recent information available. Brooke (2004) estimated the global population size to be 500 000 individuals and Del Hoyo et al. (1992) provide a figure of 100 000 – 150 000 breeding pairs. It is estimated that the number of adult birds breeding annually on Prince Edward Island is 10 000 (Ryan and Bester 2008), but indications are that this estimate is from an earlier unknown source and are dated. Breeding on Marion Island is suspected but has not been confirmed (Cooper and Brown 1990, McClelland et al. 2013). Dilley et al. (2017) indicates that the species was probably extirpated from Marion Island due to cat predation. Confidence in the regional population estimate is low.
Trend Justification
The global population is suspected to be in decline owing to light pollution (BirdLife International 2018). Preston et al (2019) have indicated that the species is possibly extirpated on Marion Island due to cat or mice predation. Despite uncertainties around size of the Marion Island population, future population projections based on extinction horizon estimates suggest that significant reductions may occur within the next three generations (Preston et al. 2019), justifying careful consideration under Criterion A3 (Lee 2025). Ongoing monitoring is essential to validate these projections and determine whether the species is experiencing measurable population decreases.
Biology & Ecology
Taxonomy
Originally placed in the genus Thalassidroma but has since been moved to Fregetta (Robertson et al. 2016). Two subspecies are recognised: F. tropica tropica has a more circumpolar and Southern Ocean distribution, while F. t. melanoleuca occurs on Tristan da Cunha and Gough islands. The taxonomy of the latter is poorly understood (Onley and Scofield 2007), especially in regard to affinities to the White-bellied Storm-petrel F. grallaria.
Identification
20 cm, 50–58 g. A robust storm-petrel characterised by a dark line along the mid-plane of the otherwise white belly. Females usually larger than males but otherwise alike. The head, neck and back are black or dark brown. Mantle, scapulars, upperwing coverts and flight feathers blackish brown. Rump white. Tail dark. Central underwing coverts white; undersides of remiges plus leading underwing coverts dark. Throat, upper breast, vent and undertail coverts blackish brown, connected by black central line down belly, although this varies from completely absent to very bold. Eyes, bill and legs black. Juveniles are similar but have pointed outer primaries and white tips to loral feathers (Ryan 2005).
Distribution
This species has a circumpolar distribution, with recorded breeding sites at ten Subantarctic islands or island groups (South Georgia, South Orkney, South Shetland, Bouvet, Prince Edward, Crozet, Kerguelen, Auckland, Bounty and Antipodes islands). Black-bellied Storm-petrels breed in the austral summer (from November) and can disperse as far north as the equator in winter (Onley and Scofield 2007). Within the region, the species breeds on Prince Edward Island and is thought to breed on Marion Island as two juvenile birds with traces of down, were captured in 2009, coming from the interior of the island (McClelland et al. 2013). It is a common passage migrant in waters off the South African mainland, occurring mainly in spring and autumn (Ryan 2005).
Ecology
The species forages over the open ocean and associates with land only when breeding (Ryan 2005). This species forages for fish and small crustaceans in cool currents (Hahn 1998) although they can also forage in a wide range of water temperatures (0–30° C) (Ryan 2005). They forage in groups, often associating with whales, seals, seabirds or fishing vessels. In South African waters, they are common for two brief periods (approximately 6–8 weeks) during spring and autumn, where they are found along the continental shelf-break (500–1000 m deep) and especially around the Agulhas Retroflection (Ryan 2005). Breeding begins in November at loose colonies on bare slopes, in thick vegetation, or peat. One egg is laid in a burrow or rocky crevice (Del Hoyo et al. 1992). A generation length of 5.1 years is provided by Bird et al. (2020).
Threats & Conservation
Threats
Predation by alien rats, mice and cats at some colonies may be a problem. It is thought that this bird was extirpated from Marion Island due to predation by cats (van Aarde 1980). Since the removal of cats, there is some evidence that this species is returning to breed (Hagen 2015). They may be vulnerable to predation by introduced mice on Marion Island. Light pollution from the research base on Marion Island may blind individuals causing them to collide with unseen structures, injuring or killing them (RM Wanless pers obs). Incidents where mortalities have been caused by lights on vessels operating in the Southern Ocean have been recorded (Black 2005, Ryan et al. 2021). Oil pollution events are a serious risk for a species that actively investigates oil from fish/whales, particularly in search of food.
Conservation Measures Underway
No conservation measures are underway since the removal of introduced cats from Marion Island, which has proven beneficial to a number of burrowing seabirds nesting on the island, although the ongoing presence of house mice may have reduced the fully recovery potential (Dilley et al. 2017). Many general conservation actions and strict guidelines are in place to protect the islands and their native ecosystems. In addition, the Prince Edward Islands are listed as a Ramsar Wetland of International Importance, 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
The proposed eradication of introduced mice from Marion Island should be conducted, which may encourage this species to resume breeding on this island.
Research Priorities and Questions
- Determine if the species breeds on Marion Island.
- Determine whether mice impact the species at Marion Island.
- Regular population censusing is needed.
- The degree of movement of birds between the Prince Edward Island colony and other colonies in the Subantarctic region should be assessed.
Contributors & References
Assessor/s
Christina Hagen
Reviewer/s
Mäelle 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. Available: 10.1111/cobi.13486.
BirdLife International. 2018. Fregetta tropica. The IUCN Red List of Threatened Species 2018: e.T22698459A132648556. Available: https://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T22698459A132648556.en. [Accessed on 16 November 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.
Cooper J, Brown C. 1990. Ornithological research at the Subantarctic Prince Edward Islands: a review of achievements. South African Journal of Antarctic Research 20: 40–57.
Del Hoyo J, Elliot A, Sargatal J. 1992. Handbook of the Birds of the World. Vol. 1. Barcelona: Lynx Edicions.
Dilley BJ, Schramm M, Ryan PG. 2017. Modest increases in densities of burrow-nesting petrels following the removal of cats (Felis catus) from Marion Island. Polar Biology 40: 625–637.
Hagen CT. 2015 Black-bellied Storm Petrel Fregetta tropica. In: Taylor MR, Peacock F, Wanless RW (eds), The Eskom Red Data Book of Birds of South Africa, Lesotho and Swaziland. Johannesburg, South Africa: BirdLife South Africa. pp 336–337.
Hahn S. 1998. The food and chick feeding of Black-bellied Storm Petrel (Fregetta tropica) at King George Island, South Shetlands. Polar Biology 19: 354–357.
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.
McClelland GT, Cooper J, Chown SL. 2013. Evidence of breeding by Diving Petrels and Storm Petrels at Marion Island of the eradication of feral cats. Ornithological Observations 4:90–93.
Onley D, Scofield P. 2007. Albatrosses, Petrels and Shearwaters of the World.
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.
Robertson BC, Stephenson BM, Ronconi RA, Goldstien SJ, Shepherd L, Tennyson A, Carlile N, Ryan PG. 2016. Phylogenetic affinities of the Fregetta storm-petrels are not black and white. Molecular Phylogenetics and Evolution 97:170–176.
Ryan PG. 2005. Black-bellied Storm-Petrel Fregetta tropica. In: Hockey PAR, Dean WRJ, Ryan PG (eds), Roberts – Birds of Southern Africa, 7th Edn. Cape Town, South Africa: The Trustees of the John Voelcker Bird Book Fund. pp 636–637.
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.
Ryan PG, Ryan EM, Glass JP. 2021. Dazzled by the light: the impact of light pollution from ships on seabirds at Tristan da Cunha. Ostrich 92:218–224.
van Aarde RJ. 1980. The diet and feeding behaviour of feral cats, Felis catus, at Marion Island. South African Journal of Wildlife Research 10: 123–128.
Citation
Hagen C 2025. Black-bellied 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/black-bellied-storm-petrel/
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