Page 332 - Atlas Sea Birds Ver1

Table 1. Estimated number of pairs of Leach’s Storm Petrels Storm Petrels bred in cavities in dry stone walls around
breeding at different localities, and overall, in South Africa in the settlement (Whittington et al. 2001) where Kelp Gulls
different years, 1995–2022. ‘?’ indicates that breeding may have (L. dominicanus) did not breed (Crawford and Underhill.
taken place. Sources of information are indicated in the main text 2005). The loss of the Dyer Island colony coincided with
Crowned Cormorants (Microcarbo coronatus) initiating
Year Jutten Dassen Dyer Total nesting on the walls. At Dassen Island, the petrels also
Island Island Island bred near the settlement, where Kelp Gulls occur but nest
1995 17 17 in low densities. Two Barn Owls (Tyto alba) that foraged
1996 19 19 in the vicinity of the petrel nests and were suspected to
1997 1 17 18 have killed two Leach’s Storm Petrels were caught and
1998 0 20 20 released on the mainland at some distance from the island.
However, Barn Owls are still encountered at Dassen Island
1999 1 ? (CN unpubl.). A lack of suitable nesting habitat in areas
2000 5 0 7 12 where Kelp Gull densities are low may be limiting the South
2001 6 1 5 12 African population. Offshore gas operations occur between
2002 3 2 2 7 Dyer and St Croix islands, but the foraging grounds of birds
2003 0 4 5 9 that breed in South Africa are unknown and where they
2004 0 4 1 5 spend the non-breeding part of their annual cycle has yet to
be discovered. In 2018, highly pathogenic avian influenza
2005 0 ? 0 (HPAI) affected nine species of seabird in South Africa,
2006 0 5 0 5 including seven that breed at coastal islands (Khomenko
2007 0 5 0 5 et al. 2018). Such contagious diseases are regarded as a
2008 0 4 0 4 threat to all seabirds breeding in the region.
2009 0 4 0 4
2010 0 4 0 4 References
2011 0 5 0 5 Ainley DG, Henderson RP, Strong CS. 1990. Leach’s Storm Petrel
2012 0 4 0 4 and Ashy Storm Petrel. In: Ainley DH, Boekelheide RJ (eds).
2013 0 3 0 3 Seabirds of the Farallon Islands. Stanford University Press,
Stanford: pp. 128–162.
2014 0 4 0 4 BirdLife International. 2020. Guidelines for the application of the
2015 0 4 0 4 IBA criteria. Final version, July 2020. 18 pp. Downloaded
2016 0 4 0 4 from http://datazone.birdlife.org/ on 20 May 2022.
2017 0 4 0 4 BirdLife International. 2022. Species factsheet: Hydrobates
leucorhous. Downloaded from http://www.birdlife.org on 25
2018 0 5 0 5 October 2022.
2019 0 5 0 5 Crawford RJM, Underhill LG. 2005. Leach’s Storm Petrel
2020 0 6 0 6 Oceanodroma leucorhoa. In: Hockey PAR, Dean WRJ, Ryan
th
2021 0 4 0 4 PG (eds). Roberts Birds of Southern Africa, 7 Edition. John
Voelcker Bird Book Fund, Cape Town: pp. 639–640.
2022 3-4 Crawford RJM, Whittington PA, Dyer BM, Upfold L. 2007. Trends
in numbers of Leach’s Storm Petrel, Hartlaub’s Gull and Swift
the South African population presently meets criteria C1 and Roseate Terns breeding in South Africa. In: Kirkman SP
(number of mature individuals < 250 and an observed, (ed.). Final Report of the BCLME (Benguela Current Large
estimated or projected continuing decline of at least 25% Marine Ecosystem) Project on Top Predators as Biological
in 1 generation) and D (< 50 mature individuals) of the Indicators of Ecosystem Change in the BCLME. Avian
International Union for Conservation of Nature (IUCN) for Demography Unit, Cape Town: pp. 211–213.
classification as Critically Endangered (IUCN 2022).
Important Bird and Biodiversity Areas are identified
through the use of specific criteria. Criterion A1 is that
‘the site is known or thought regularly to hold significant
numbers of a Globally Threatened species’ (BirdLife
International 2020). Guidelines for the application of IBA
criteria recommend that to meet A1 a site must support:
at least 1 individual of a CR or Endangered species with
a global population of 1,500 individuals or fewer (BirdLife
International 2020). Should the same criterion apply in a
regional context, Dassen Island would classify as an IBA
for South Africa’s population of Leach’s Storm Petrel.
Amongst major threats to Leach’s Storm Petrels globally
are predation by feral cats (Felis catus), rats (Rattus spp.),
and native avian predators, including Larus gulls and, at
western North Atlantic colonies, an overlap of foraging
ranges during breeding with offshore oil and gas operations Photo of a Leach’s Storm Petrel taken with a camera trap at
(BirdLife International 2022). At Dyer Island, Leach’s Dassen Island (photo M van Onselen)

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