The status and conservation of Cape Gannets Morus capensis
Sherley, R; Crawford, R; Dyer, B; et al.Kemper, J; Makhado, A; Masotla, M; Pichegru, L; Pistorius, P; Roux, J-P; Ryan, P; Tom, D; Upfold, L; Winker, H
Date: 6 December 2019
Article
Journal
Ostrich: Journal of African Ornithology
Publisher
Taylor & Francis
Publisher DOI
Abstract
The Cape Gannet Morus capensis is one of several seabird species that are endemic to the
Benguela upwelling ecosystem (BUS), whose populations recently decreased leading to
unfavourable Red List classifications. Application of JARA, a Bayesian state-space tool for IUCN
Red List assessment, to updated information on areas occupied ...
The Cape Gannet Morus capensis is one of several seabird species that are endemic to the
Benguela upwelling ecosystem (BUS), whose populations recently decreased leading to
unfavourable Red List classifications. Application of JARA, a Bayesian state-space tool for IUCN
Red List assessment, to updated information on areas occupied by and nest densities of breeding
Cape Gannets at their six colonies suggested the species should be classified as Vulnerable.
However, the rate of decrease of Cape Gannets in their most recent generation exceeded that of
the previous generation, primarily as a result of large decreases at Bird Island, Lambert’s Bay,
and Malgas Island off South Africa’s west coast. Since the 1960s, there has been an ongoing
redistribution of the species from northwest to southeast so that c. 70% of the species now occurs
at Bird Island, Algoa Bay, on the eastern border of the BUS. Recruitment rather than adult survival
may be limiting the present population, although information on demographic parameters and
mortality in fisheries is lacking for colonies in the northern BUS. Major present threats to the
species include a substantially decreased availability of their preferred prey in the west, heavy
mortality of eggs, chicks and fledglings at and around colonies inflicted by Cape Fur Seals
Arctocephalus pusillus and other seabirds, substantial disturbance at colonies caused by Cape
Fur Seals attacking adults ashore, oiling and disease.
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