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Seabird Species

Leach's Storm Petrel

PA Whittington1, BM Dyer2 & LG Underhill1
1Animal Demography Unit
2Marine and Coastal Management, Private Bag X2, Rogge Bay, 8012, South Africa

  Leach's Storm Petrel
Photo Les Underhill
An adult Leach's Storm Petrel Oceanodroma leucorhoa, mistnetted for ringing on Dassen Island

Until the mid 1990s, the status of Leach's Storm Petrel in southern African seas was that of a rare visitor which breeds in the northern hemisphere only. The known breeding colonies were along the northern Pacific Rim, from Japan through Alaska to California, and along the north Atlantic, from the northeastern USA through Iceland and Scotland to Norway.

In October 1995, a small group of Leach's Storm Petrels was discovered on Dyer Island off the south coast of South Africa. Their behaviour, occupation of suitable nest sites and the capture of a bird with a well- developed brood patch, suggested that the birds could be breeding.

In November 1996, breeding was confirmed when an adult, occupying a cavity in a dry-stone wall, was found to be incubating an egg. At least 19 birds were heard calling from the network of stone walls in the vicinity. In February 1997, the nest cavity was again examined and found to contain a chick, estimated to be between 30 and 45 days old. The chick had a covering of down over its head and body, the wing coverts were 'in pin' and the remiges and rectrices were well developed. Indications were that the chick had fledged by mid-March. Chicks were heard calling in two other nest cavities on the February visit.

 
Leach’s Storm Petrel
   
 
Leach’s Storm Petrel
Photos Les Underhill
Leach’s Storm Petrel Oceanodroma leucorhoa at Dyer Island. The grey line down the centre of the rump, visible in the top photograph, is diagnostic

Between 1997 and 2000, the population has remained stable at about 20 pairs, and breeding was again confirmed in 1998 and 1999. In February 1998, six nests, each with a chick, were located and two chicks were ringed. One of these was retrapped on the island on 22 October 2001. Another two chicks were ringed in February 1999. Between November 2000 and January 2001, 13 adult Leach's Storm Petrels were mist-netted and ringed, more than doubling the total number of adults of this species ringed in South Africa. A few more were ringed in October and November 2001, but most birds caught were retraps from the previous year. Biometric measurements were made, and first indications are that the South African Leach's Storm Petrels are slightly larger than any of the subspecies elsewhere in the world.

At least four adults were heard calling overhead at Dassen Island, off South Africa's west coast, in November 1996. At least two birds have been heard calling there at suitable nest sites in subsequent years. The birds are almost certainly breeding at this locality too, although this has still to be confirmed. In October 2000, four Leach's Storm Petrels were heard calling from likely nest sites in a stone wall at Jutten Island, also on the west coast, and a fifth site appeared to be occupied. Previous searches of this stretch of wall, at the same time of year and in similar weather conditions, had failed to locate any Leach's Storm Petrels. Six birds were heard calling here in October 2001.

These observations represent the first confirmed breeding of this species on the African continent and in the Southern Hemisphere.

Acknowledgements

The Western Cape Nature Conservation Board allowed access to Dyer and Dassen Islands and provided logistical support. The Marine and Coastal Management division of the Department of Environmental Affairs and Tourism provided transport to the islands. South African National Parks kindly allowed access to Jutten Island.

Further reading:

  • Ryan PG, Whittington PA 1997. Leach's Storm Petrel Oceanodroma leucorhoa. In: Harrison JA et al. (eds) The Atlas of Southern African Birds. Vol 1. Non-passerines. Johannesburg: BirdLife South Africa: 22-23.
  • Whittington PA, Dyer BM 1995. A new breeding seabird for Africa? Bird Numbers 5: 18-19.
  • Whittington PA, Dyer MB, Crawford RJM 1998. Leach's Storm Petrel: further news from the islands. Bird Numbers 7(1): 20.
  • Whittington PA, Dyer BM, Crawford RJM, Williams AJ 1999. First recorded breeding of Leach's Storm Petrel Oceanodroma leucorhoa in the Southern Hemisphere, at Dyer Island, South Africa. Ibis 141: 327-330.
  • Whittington PA, Dyer BM, Crawford RJM 1999. The walls reveal their secrets. Africa - Birds & Birding 4(1): 33.
  • Whittington PA 1998. Little piece of ringing history. Safring News 27(1-2): 43
  • Whittington PA, Dyer BM 2000. Atlas updates. Leach's Storm Petrel. Bird Numbers 9(2): 24.
  • Whittington PA, Dyer BM, Underhill LG 2001. Leach's Storm Petrel breeding in South Africa. Bulletin of the African Bird Club 8: 134.
Leach's Storm Petrel
Photo Les Underhill
This is one of the dry stone walls on Dyer Island within which Leach's Storm Petrels have their nests