Volume 47, No. 2

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Population estimates of burrow-nesting petrels breeding at the Nightingale Island group, Tristan da Cunha Archipelago


11FitzPatrick Institute of African Ornithology, DST/NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa *(
2Conservation Department, Government of Tristan da Cunha, Edinburgh of the Seven Seas, Tristan da Cunha TDCU 1ZZ, UK (South Atlantic Ocean)
3Current address: Government House, Stanley, Falklands, FIQQ 1ZZ, UK (South Atlantic Ocean)


DILLEY, B.J., DAVIES, D., MITHAM, A., GLASS, T., REPETTO, J., SWAIN, G. & RYAN, P.G. 2019. Population estimates of burrow-nesting petrels breeding at the Nightingale Island group, Tristan da Cunha Archipelago. Marine Ornithology 47: 267 - 275

Received 11 July 2019, accepted 10 August 2019

Date Published: 2019/10/15
Date Online: 2019/09/19
Key words: Great Shearwaters Ardenna gravis, burrow densities, petrel survey, seabird exploitation


Nightingale is a group of three small, uninhabited islands in the central South Atlantic Ocean. The islands are free of introduced mammals and are largely pristine, supporting two endemic land birds as well as globally important populations of several species of seabirds. Seven species of burrow-nesting petrels are known to breed on the islands, including roughly 40 % of the world's population of Great Shearwaters Ardenna gravis. We estimated burrow densities by systematically searching for their burrows in 5×5-m quadrats across the main island in the austral summer of 2015. A total of 1 789 petrel burrows fell within the 75 sample quadrats with an average density of 0.95 burrows∙m-2, suggesting that upwards of four million petrels breed on the main island. Burrow densities and occupancy rates were extrapolated by species for each habitat type to generate population estimates: Great Shearwaters 2.34 million burrows (1.82 million pairs, 95 % CI 1.67-1.97 million); Broad-billed Prions Pachyptila vittata a minimum of 83 000 burrows (with many more pairs breeding in rock crevices, total estimate 100 000-500 000 pairs), White-faced Storm Petrels Pelagodroma marina 17 800 burrows (11 700 pairs, 95 % CI 4 700-16 600), Soft-plumaged Petrels Pterodroma mollis 12 100 burrows (estimated 8 000-10 000 pairs), Fregetta Storm Petrels F. grallaria/tropica 6 600 burrows (estimated 5 000 pairs), Common Diving Petrels Pelecanoides urinatrix 3 900 burrows (estimated 5 000 pairs), and Subantarctic Shearwaters Puffinus elegans an estimated 1 000 pairs. Although Great Shearwater burrow densities and occupancies were lowest in the areas historically used for exploitation of chicks and eggs (ongoing, but now monitored), these results suggest the great shearwater population on Nightingale Island has remained relatively stable since the first estimates in the 1950s.


BERRUTI, A. & HUNTER, S. 1986. Some aspects of the breeding biology of Salvin's Prion Pachyptila vittata salvini at Marion Island. Marine Ornithology 13: 98-106.

BIRDLIFE INTERNATIONAL. 2018. Ardenna gravis. The IUCN Red List of Threatened Species 2018: e.T22698201A132633747. Cambridge, UK: International Union for Conservation of Nature. [Available online at: Accessed 13 June 2019.]

BOOTH, A.M., MINOT, E.O., IMBER, M.J. & FORDHAM, R.A. 2000. Aspects of the breeding ecology of the North Island little shearwater Puffinus assimilis haurakiensis. New Zealand Journal of Zoology 27: 335-345.

BROOKE, M. De L. 1990. The Manx Shearwater. London, UK: T & A.D. Poyser.

CAMPOS, A.R. & GRANADEIRO, J.P. 1999. Breeding biology of the White-faced Storm petrel on Selvagem Grande Island, north-east Atlantic. Waterbirds 22: 199-206.

CANTY, A. & RIPLEY, B. 2014. Boot. Bootstrap R (S-Plus) Functions. R package version 1.3-22. 

CUTHBERT, R. 2004. Breeding biology of the Atlantic Petrel, Pterodroma incerta, and a population estimate of this and other burrowing petrels on Gough Island, South Atlantic Ocean. Emu 104: 221-228.

CUTHBERT, R.J. 2005. Breeding biology, chick growth and provisioning of Great shearwaters Puffinus gravis at Gough Island, South Atlantic Ocean. Emu 105: 305-310.

DILLEY, B.J., SCHRAMM, M. & RYAN, P.G. 2017. Modest increases in densities of burrow-nesting petrels following the removal of cats Felis catus from Marion Island. Polar Biology 40: 625-637.

ELLIOTT, H.F.I. 1957. A contribution to the ornithology of the Tristan da Cunha group. Ibis 99: 545-586.

FRASER, M.W., RYAN, P.G. & WATKINS, B.P. 1988. The seabirds of Inaccessible Island, South Atlantic Ocean. Marine Ornithology 16: 7-33.

HAGEN, Y. 1952. Birds of Tristan da Cunha. Results of the Norwegian Scientific Expedition to Tristan da Cunha 1937-38. 20: 1-248.

PAYNE, M.R. & PRINCE, P.A. 1979. Identification and breeding biology of the diving petrels Pelecanoides georgicus and Pelecanoides urinatrix exsulans at South Georgia. New Zealand Journal of Zoology 6: 299-318.

QUILLFELDT, P. & PETER, H.U. 2000. Provisioning and growth in chicks of Wilson's storm-petrels Oceanites oceanicus on King George Island, South Shetland Islands. Polar Biology 23: 817-824.

R DEVELOPMENT CORE TEAM, 2018. R: A language and environment for statistical computing. Vienna, Austria: The R Foundation for Statistical Computing.

RICHARDSON, M.E. 1984. Aspects of the ornithology of the Tristan da Cunha group and Gough Island, 1972-1974. Cormorant 12: 123-201.

ROBERTSON, B.C., STEPHENSON, B.M., RONCONI, R.A., GOLDSTIEN, S., SHEPHERD, L., TENNYSON, A., CARLILE, N. & RYAN, P.G. 2016. Phylogenetic affinities of the Fregetta storm-petrels are not black and white. Molecular Phylogenetics and Evolution 97: 170-176.

ROBSON, B., GLASS, T., GLASS, N., GLASS, J., GREEN, J., REPETTO, C., RODGERS, G., RONCONI, R.A., RYAN, P.G., SWAIN, G. & CUTHBERT, R.J. 2011. Revised population estimate and trends for the endangered Northern Rockhopper Penguin Eudyptes moseleyi at Tristan da Cunha. Bird Conservation International 21: 454-459.

ROWAN, M.K. 1952. The Great Shearwater Puffinus gravis at its breeding ground. Ibis 94, 97-121.

ROWAN, M.K. 1965. Regulation of seabird numbers. Ibis 107: 54-59.

RYAN, P.G. 2007. Field Guide to the Animals and Plants of Tristan da Cunha and Gough Island. Newbury, UK: Pisces Publications.

RYAN, P.G. & MOLONEY, C.L. 1991. Prey selection and temporal variation in the diet of Subantarctic Skuas at Inaccessible Island, Tristan da Cunha. Ostrich 62: 52-58.

RYAN, P.G. & MOLONEY, C.L. 2000. The status of Spectacled Petrels Procellaria conspicillata and other seabirds at Inaccessible Island. Marine Ornithology 28: 93-100.

RYAN, P.G. & RONCONI, R.A. 2010. The Tristan Thrush Nesocichla eremita as seabird predator. Ardea 98: 241-243.

RYAN, P.G., DEAN, W.R.J., MOLONEY, C.L., WATKINS, B.P. & MILTON, S.J. 1990. New information on seabirds at Inaccessible Island and other islands in the Tristan da Cunha group. Marine Ornithology 18: 43-54.

RYAN, P.G., GLASS, N. & RONCONI, R.A. 2011. The plants and birds of Stoltenhoff and Middle Islands, Tristan da Cunha. Polar Record 47: 86-89.

RYAN, P.G., BOURGEOIS, K., DROMZÉE, S. & DILLEY, B.J. 2014. The occurrence of two bill morphs of prions Pachyptila vittata on Gough Island. Polar Biology 37: 727-735.

SCHRAMM, M., 1986. Burrow densities and nest site preferences of petrels (Procellariidae) at the Prince Edwards Islands. Polar Biology 6: 63-70.

ST. HELENA, 2006. Legislation: The Conservation of Native Organisms and Natural Habitats (Tristan da Cunha) Ordinance 2006. The St. Helena Government Gazette Extraordinary 44 (3 February 2006).

WACE, N.M. & HOLDGATE, M.W. 1976. Man and Nature in the Tristan da Cunha Islands (No. 6). Morges, Switzerland: International Union for Conservation of Nature and Natural Resources.

WARHAM, J. 1990. The Petrels - Their Ecology and Breeding Systems. London, UK: Academic Press.

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