Crozet Shag
Leucocarbo melanogenis
Number Of Mature
Individuals (Regional)
580
Regional
Population Trend
Decreasing
2025
Regional Category
Endangered
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CONTENTSOverview
Names
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IOC English Name: |
Crozet Shag |
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SA & IOC Scientific Name: |
Leucocarbo melanogenis |
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BirdLife International Taxonomy (scientific name): |
Leucocarbo melanogenis |
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Order: |
SULIFORMES |
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Family: |
Phalacrocoracidae |
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Species name author: |
Blyth 1860 |
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Afrikaans: |
Crozet Duiker |
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Sesotho (South Africa): |
Ntodi ya Crozet |
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Sesotho (Lesotho): |
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Siswati: |
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Zulu: |
iphishamanzi laseMarion |
Current Assessment Status
|
2025 Regional Category [Criteria] |
EN [A2abc; B2ab(iii, v)] |
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2024 Global Category [Criteria] |
Not recognised as a full species |
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Population size (Regional) |
c. 290 pairs |
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Population size (Global) |
c. 1115 pairs |
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Distribution size (EOO) (Regional) km2 |
377 (breeding; foraging) |
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Distribution size (EOO) (Global) km2 |
c. 2172 |
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Distribution size (AOO) (Regional) km2 |
334 (breeding) |
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Generation time |
10.67 years (calculated in Ecology section) |
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Status change reason |
Genuine Change in Status |
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Migrant (in the region) |
No |
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Regional endemic |
No |
Historic Listing Information
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2000 Regional Status |
VU [C2b; D2] |
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2015 Regional Status |
CR [A2ab] |
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Status change reason (if applicable) |
Genuine Change in Status |
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2015 Population size (Regional) |
230 pairs |
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2015 Global Status |
Not recognised as a full species |
Reason for Inclusion
Reason for Inclusion in the Assessment
South Africa’s Prince Edward Islands (PEIs) support c. 290 pairs of Crozet Shags Leucocarbo [atriceps] melanogenis, which is roughly 26% of the global population of c. 1115 pairs. Elsewhere, the species breeds only at the Crozet Islands, where the population numbered c. 825 pairs (Jouventin et al. 1984). The species was listed as regionally Vulnerable in 2000, then regionally Critically Endangered in 2015.
Category Justification
Category Justification
Based on data collected at Marion Island since 1987/88, the regional population of Crozet Shag satisfies the criteria for regionally Endangered under the reduction in population size Criterion A2abc. A population size reduction of ≥ 60% has been observed within the three-generation period to 2021/22, based on direct counts of breeding pairs and a reduction in habitat quality/food availability. Additionally, a 75% decrease was observed between 1994/95 and 2021/22 (27 years), which would equate to about 81% in 3 generations including the future if the trend continues – and could return the species to a Critically Endangered state under Criteria A4. As the breeding area of Crozet Shag is <500 km2, together with just two locations (Prince Edward and Marion Islands), together with a documented decreasing population, Endangered by Criterion B2ab(iii, v) is met.
Population Justification
The most recent counts of Crozet Shags breeding at Prince Edward and Marion islands were of 81 pairs in 2008/09 (Crawford et al. 2009) and 208 pairs in 2021/22 (Department Forestry, Fisheries and Environment, DFFE, unpubl data), respectively. The sum of these counts is c. 290 pairs, which is the best estimate of the present population at South Africa’s PEIs. It is worth noting that a flight around PEI in the late afternoon of May 2019 revealed just 69 shags roosting ashore (B. Dyer, pers comm).
Trend Justification
In the 1951/52 breeding season, there were at least 178 nests at Marion Island (Crawford et al. 2003). In 1987/88, 589 pairs bred at Marion Island (Cooper and Brown 1990). In 1994/95, annual monitoring of numbers of Crozet Shags breeding at Marion Island commenced. In that season, 841 pairs bred, which decreased to 344 pairs in 2001/02 (Crawford et al. 2003) and to 220 pairs in 2003/04 (Crawford et al. 2009). Numbers then increased to 598 pairs in 2006/07, before decreasing again to 148 pairs in 2012/13, the lowest count yet recorded (Crawford et al. 2009, 2014), and 208 pairs in 2021/22 (DFFE unpubl data). At PEI, 120 pairs were recorded breeding in 1984 (Crawford et al. 2003) decreasing by 33% to 81 pairs in 2008 (Crawford et al. 2009), and potentially by 43% to 69 pairs in 2019. At Marion Island, the decrease over the past 3 generations (1987/88 to 2021/22) was 65%, and the decrease over the period of annual monitoring, from 1994/95 to 2021/22, was 75% in 27 years, which would equate to about 81% in three generations including the future if the trend continues using an exponential decay model.
Biology & Ecology
Taxonomy
The Crozet Shag Leucocarbo melanogenis forms part of the Imperial Cormorant L. atriceps super-species complex. Following the precautionary principle, it has been treated as a separate species. Further research is required to resolve the taxonomic status of this complex.
Identification
70 cm, 2.0–2.6 kg. Adults blue-black above and white below. Long white wing-bar on the upper wings. Bill is black. Gular skin a dirty yellow. Caruncles on forehead bright yellow. Iris brown with bright blue fleshy eye-ring. Feet pink. Immatures and juveniles generally brown backed and lack distinct colour on the face. Iris brown and eye ring grey. Birds usually silent at sea, but utter a contact honk, similar to King Penguins, periodically while foraging (Marchant and Higgins 1990). At roosts and during breeding, they utter guttural sounds that are similar to White-breasted Cormorants (B Dyer, pers obs).
Distribution
Found only at the PEI and Crozet archipelagos in the south-west Indian Ocean. The surface areas of Marion and Prince Edward islands are 290 km2 and 45 km2, respectively, totalling 335 km2. This was used as the Area of Occupancy (AOO), although Crozet Shags use only small portions of these islands. The species forages within about 400 m of the shore, mainly on the seabed (Cooper 1985). The shore lengths of Marion and Prince Edward islands are c. 72 km and 34 km, respectively, totalling 106 km. Therefore, the foraging extent of shags around the islands is about 42 km2, which when added to the AOO, suggests an Extent of Occurrence (EOO) of c. 377 km2.
Ecology
Crozet Shags bred coastally on cliff ledges and rock stacks at 44 known sites around Marion Island (in 2013/14 breeding was reported from only nine sites) and at 10 sites around PEI. On Marion Island, sites change, and some sites are no longer used. Of the 44 known sites since 1994, a range of 9–32 (mean 21.5) sites are used annually (B Dyer, pers comm). Breeding takes place in summer (Marchant and Higgins 1990). Nests are built with grass (Dyer and Crawford 2015). The median age at first breeding (A) of Crozet Shags was four years (Crawford et al. 2003) with average breeding success ranging from 0.07–1.28 chicks fledged per pair (Crawford et al. 2009). Adult survival (ϕ a) was maximally 0.85 p. a. (Crawford et al. 2003) and there has been a recapture of a 16-year-old bird (B Dyer, pers comm). Given generation length (G) = A + (1 / (1 − ϕ a)) (Birdlife International 2000), G = 10.67 y. Their diet consists of a variety of benthic fish, an octopus (perhaps two species), a decapod shrimp and several marine other invertebrate items (Blankley 1981, Espitalier-Noel et al. 1988, Crawford et al. 2003).
Threats & Conservation
Threats
Decreases at Marion Island have been influenced by poor breeding success (Crawford et al. 2003, 2009). Numbers breeding between 1994/95 and 2012/13 were significantly correlated with numbers of Gentoo Penguins Pygoscelis papua breeding at Marion Island (Crawford et al. 2014). The two species have similar foraging distributions and diets, and their decreases may have been influenced by reduced food availability (Crawford et al. 2003, 2009, 2009). The dips in productivity may be linked to the “Ashmole’s Halo” phenomenon, where prey is depleted through predation (Ashmole 1963). Storms may wash nests off cliffs (Crawford et al. 2003). Antarctic Fur Seals Arctocephalus gazella are increasing at both Marion and Prince Edward islands (Bester et al. 2009) and their predation on Crozet Shags is a potential threat, as are avian predation on eggs and chicks and avian disease. Crozet Shags may be disturbed by humans in close proximity and by helicopters, particularly during breeding. There is a small but non-trivial risk of diesel spills while offloading fuel on relief voyages. Disturbance at roosts may also affect prospecting birds at the start of breeding. Other research/monitoring groups may cause disturbance when doing their work. Zone 4 is not always strictly applied (B Dyer, pers comm). An increase in base waste is creeping into beach debris records, potentially causing ingestion or entanglement.
Conservation Measures Underway
There is no access to the PEIs (Zone 5 PERMIT) without a permit issued by South Africa’s DFFE. At Marion Island, breeding sites are categorised according to the Prince Edward Islands Management Plan as Zone 4. This is the strictest conservation area; no helicopter movement is permitted overhead, no casual access permitted, and only limited research allowed. There are no visits to PEI except for bona fide research and conservation purposes. There are strict processes in place to avoid diesel and fuel spills at sea.
Conservation Measures Proposed
Monitoring of numbers breeding and breeding success at Marion Island should continue. A population census at PEI should be conducted. Restrictions regarding access to breeding sites should remain. The occasional helicopter trips in November/December should be severely restricted to only ship-to-base in the narrowest window. At these times, tourist-type flights and show-boating activities should not be permitted too. Waste disposal needs tightening.
Research Priorities and Questions
- A main priority which needs to be urgently addressed is clarity on the taxonomic status of birds breeding at the PEIs. If birds at the PEIs are a different species to those at the Crozet Islands, the species will be of heightened global conservation concern.
- Understanding inter-annual and inter-colony differences in diets and relating these to breeding performance is required in order to understand the population dynamics of the species. Questions such as whether the size of prey has changed over time, and the proportion of large vs small prey are important to answer.
- Further information is needed on juvenile and adult survival and participation in breeding.
- Factors causing periodic relocation of colonies require investigation. Collecting several complete nests when breeding is complete and investigating their parasite loads is recommended.
Contributors & References
Assessor/s
AB Makhado, RJM Crawford
Reviewer/s
Bruce Dyer
References
Ashmole NP. 1963. The regulation of numbers of tropical oceanic birds. Ibis 103b: 458–473.
Bester MN, Ryan PG, Visagie J. 2009. Summer survey of fur seals at Prince Edward Island, southern Indian Ocean. African Journal of Marine Science 31: 451–455.
BirdLife International. 2000. Threatened birds of the world. Barcelona: Lynx Edicions.
Blankley WO. 1981. Marine food of Kelp Gulls, Lesser Sheathbills and Imperial Cormorants at Marion Island (subantarctic). Cormorant 9: 77–84.
Cooper J. 1985. Foraging behaviour of non-breeding Imperial Cormorants at the Prince Edward Islands. Ostrich 56: 96–100.
Cooper J, Brown CR. 1990. Ornithological research at the sub-Antarctic Prince Edward Islands: a review of achievements. South African Journal of Antarctic Research 20: 40–57.
Crawford RJM, Cooper J, Dyer BM, Wolfaardt AC, Tshingana D, Spencer K, Petersen SL, Nel JL, Keith DG, Holness CL, Hanise B, Greyling MD, du Toit M. 2003. Population, breeding, diet and conservation of the Crozet shag Phalacrocorax [atriceps] melanogenis at Marion Island, 1994/95–2002/03. African Journal of Marine Science 25: 537–547.
Crawford RJM, Ryan PG, Dyer BM, Upfold L. 2009. Recent trends in numbers of Crozet shags breeding at the Prince Edward Islands. African Journal of Marine Science 31: 427–430.
Crawford RJM, Dyer BM, Upfold L, Makhado AB. 2014. Congruent, decreasing trends of Gentoo Penguins and Crozet Shags at sub-Antarctic Marion Island suggest food limitation through common environmental forcing. African Journal of Marine Science 36: 225–231.
Dyer BM, Crawford RJM. 2015. Crozet Shag Phalacrocorax melanogenis. In: Taylor MR, Peacock F, Wanless RM (eds), The 2015 Eskom Red Data Book of Birds of South Africa, Lesotho and Swaziland. Johannesburg, South Africa. pp 46–47.
Espitalier-Noel G, Adams NJ, Klages NT[W]. 1988. Diet of the Imperial Cormorant Phalacrocorax atriceps at sub-Antarctic Marion Island. Emu 88: 43–46.
Jouventin P, Stahl JC, Weimerskirch H, Mougin J-L. 1984. The seabirds of the French subantarctic islands and Adélie Land, their status and conservation. ICBP Technical Publication 2: 609–625.
Marchant S, Higgins PJ (co-ordinators). 1990. Handbook of Australian, New Zealand and Antarctic birds. 1. Ratites to ducks. Melbourne: Oxford University Press.
Citation
Makhado AB, Crawford RJM 2025. Crozet Shag. 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/crozet-shag/
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