The Diet and Implications of Dietary Change of Cape Gannets on Bird Island, Algoa Bay

Batchelor, A L; Ross, G. J. B.

doi:10.1080/00306525.1984.9634757

Cited by 70 publications

(61 citation statements)

References 26 publications

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“…The low breeding successes recorded during our study period strongly suggest that this diet was insufficient to keep chicks alive. Indeed, Batchelor & Ross (1984) showed that Cape gannet chicks fed with fishery wastes had a lower growth rate than chicks fed with sardines, which resulted in a lower probability of survival.…”

Section: Discussionmentioning

confidence: 99%

“…They feed primarily by plunge-diving on pelagic fishes within the first 20 m of the water column (Crawford 2005), but also gather behind hake trawlers to feed on fishery wastes (Abrams 1983;Ryan & Moloney 1988). Such food has only half the calorific value of Cape gannets' natural prey (Batchelor & Ross 1984). In this context, the junk-food hypothesis ( JFH) posits that seabirds feeding on prey of low energy and nutrient content have reduced reproductive success (Piatt & Anderson 1996), because such a diet affects the growth patterns and the cognitive abilities of their offspring (Kitaysky et al 2005;Wanless et al 2005).…”

Section: Introductionmentioning

confidence: 99%

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A junk-food hypothesis for gannets feeding on fishery waste

et al. 2008

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Worldwide fisheries generate large volumes of fishery waste and it is often assumed that this additional food is beneficial to populations of marine top-predators. We challenge this concept via a detailed study of foraging Cape gannets Morus capensis and of their feeding environment in the Benguela upwelling zone. The natural prey of Cape gannets (pelagic fishes) is depleted and birds now feed extensively on fishery wastes. These are beneficial to non-breeding birds, which show reduced feeding effort and high survival. By contrast, breeding gannets double their diving effort in an attempt to provision their chicks predominantly with high-quality, live pelagic fishes. Owing to a scarcity of this resource, they fail and most chicks die. Our study supports the junk-food hypothesis for Cape gannets since it shows that non-breeding birds can survive when complementing their diet with fishery wastes, but that they struggle to reproduce if live prey is scarce. This is due to the negative impact of low-quality fishery wastes on the growth patterns of gannet chicks. Marine management policies should not assume that fishery waste is generally beneficial to scavenging seabirds and that an abundance of this artificial resource will automatically inflate their populations.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A junk-food hypothesis for gannets feeding on fishery waste

et al. 2008

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“…For example, what happens between the departure from the colony and the arrival at the first foraging zone has never been described in detail for any seabird species. We studied Cape Gannets (Morus capensis Lichtenstein, 1823; Figure 1), seabirds that breed in large colonies (Crawford et al 2007) and naturally feed on pelagic fish schools, mainly sardines (Sardinops sagax) and anchovies (Engraulis encrasicolus) (Batchelor and Ross 1984). Like other gannet species, they capture prey by plunge-diving, visually targeting their prey from the air (Lee and Reddish 1981, Ropert-Coudert et al 2004b, Machovsky-Capuska et al 2012.…”

Section: Introductionmentioning

confidence: 99%

From colony to first patch: Processes of prey searching and social information in Cape Gannets

Thiebault

Mullers

Pistorius

et al. 2014

The Auk

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“…Gaston & Jones 1998 Takahashi et al 2001;Deguchi et al 2004;Thayer & Sydeman 2007;Ito et al 2009Fisher et al 1955a, b Blount et al 2002Sorensen et al 2009Ito et al 2009Hipfner et al 20132014Takahashi et al 2001Ito et al 2009Ito et al 2009 Batchelor & Ross 1984;Takahashi et al 2001;Litzow et al 2002;Wanless et al 2005;Muller et al 2009 R …”

Section: ; Niizuma and Yamamura 2004mentioning

confidence: 99%

Assimilation efficiency and growth of Rhinoceros Auklet chicks fed with Japanese Sand Lance and krill

et al. 2015

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Abstract. The assimilation efficiency and growth of Rhinoceros AukletThe assimilation efficiency (corrected with nitrogen retention) of the sand lance-fed chicks (82.8 0.5 ) was significantly higher than the krill-fed chicks (76.6 0.6 ). During the experiment, daily mass increments of the sand lance-fed chicks were 11.0 4.7 (g/d, n 12) and of the krill-fed chicks 9.7 2.7 (g/d, n 14). Sand lance-fed chicks gained body mass significantly faster than did krill-fed chicks after controlling for the significant age effect. Krill may be inadequate for chick growth of the auklets due to the poorer lipid content, compared with sand lance.

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The Diet and Implications of Dietary Change of Cape Gannets on Bird Island, Algoa Bay

Cited by 70 publications

References 26 publications

A junk-food hypothesis for gannets feeding on fishery waste

A junk-food hypothesis for gannets feeding on fishery waste

From colony to first patch: Processes of prey searching and social information in Cape Gannets

Assimilation efficiency and growth of Rhinoceros Auklet chicks fed with Japanese Sand Lance and krill

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