Diet variability and reproductive performance of macaroni penguins Eudyptes chrysolophus at Bird Island, South Georgia

Waluda, Claire M.; Hill, Simeon L.; Peat, Helen J.; Trathan, Philip N.

doi:10.3354/meps09930

Cited by 38 publications

(44 citation statements)

References 73 publications

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“…Based on 14 d nestling mass as an indicator of diet quality, diet diversity increased when feeding conditions were sub-optimal, supporting previous observations of seabird diet breadth in relation to reproductive success and other measures of breeding conditions (e.g. Takahashi et al 2001, Hedd et al 2006, Waluda et al 2012.…”

Section: Discussionsupporting

confidence: 83%

Seabird diet changes in northern Hudson Bay, 1981-2013, reflect the availability of schooling prey

Gaston¹,

Elliott²

2014

Mar. Ecol. Prog. Ser.

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Ongoing climate change is altering Arctic marine ecosystems with major consequences for food-webs. Seabirds, by foraging over large marine areas but returning regularly to their breeding colonies, provide a good medium for tracking such changes. We studied the prey delivered to nestling thick-billed murres Uria lomvia at a colony in northern Hudson Bay, Canada, over the period 1981−2013. During that period, ice conditions in the region altered substantially, with earlier break-up and clearance. This change was not gradual but mainly occurred in the mid1990s. Breeding chronology also advanced, but not as fast as early summer ice clearance advanced. Ice conditions strongly affected diet, presumably reflecting the change in the timing of breeding relative to ice clearance. Of the dominant species in the diet, the proportion of Arctic cod Boreogadus saida decreased and the proportion of capelin Mallotus villosus increased over the 33 yr period, even after ice effects were taken into account, suggesting a progressive and cumulative effect of environmental change on the marine community. Those cumulative changes were manifested primarily in the diet representation of the most frequent taxa (cod and capelin), with variation in secondary diet components being driven by the availability of the dominant taxa. Diet diversity, representing an increase in the proportion of benthic fish (stichaeids, zoarcids, pholids and sculpins) and invertebrates (squid, amphipods and crustaceans), increased when ice cover was low, and hatching was late relative to ice break-up. Chick growth rates were low when the proportion of benthic fish was high. Hence, although it appears that growth rates are influenced by diet composition, it is more likely that they reflect the availability of the dominant schooling prey species, rather than any nutritional deficiency in benthic species.KEY WORDS: Ice cover · Climate change · Forage fish · Thick-billed murre · Uria lomvia Resale or republication not permitted without written consent of the publisher

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Section: Discussionsupporting

confidence: 83%

Seabird diet changes in northern Hudson Bay, 1981-2013, reflect the availability of schooling prey

Gaston¹,

Elliott²

2014

Mar. Ecol. Prog. Ser.

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“…In contrast, macaroni penguins remain in more northerly waters (Ratcliffe et al 2014), and may compensate for the lower availability of fish by switching to a diet that is almost entirely composed of crustaceans. The diets of macaroni penguins are then potentially enriched in 15 N during the breeding season by the inclusion of myctophid and demersal fish species (Waluda et al 2012). The blood plasma samples that represented the pre-breeding season for males were similar to those observed for males during incubation and spanned part of the range observed for males during pre-moult.…”

mentioning

confidence: 87%

“…Altered activity budgets and diet switching in this population typically results from a reduction in local krill availability (Croxall et al 1999, Waluda et al 2010. The percentage of individuals with a diet dominated by krill (> 90% of a diet sample) was lower in 2002 compared to (42% in 2002Waluda et al 2012;60% in 2012;British Antarctic Survey unpubl. data).…”

Section: Individual Consistency and Intrapopulation Variation In Resomentioning

confidence: 99%

Drivers of intrapopulation variation in resource use in a generalist predator, the macaroni penguin

Horswill¹,

Matthiopoulos²,

Ratcliffe³

et al. 2016

Mar. Ecol. Prog. Ser.

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“…This importance could be due to the component's role as an indicator of wider ecosystem state, its direct importance to ecosystem services, or its indirect importance via ecosystem structure and functioning (Zacharias & Roff 2001;Link 2010). For example, macaroni penguins in South Georgia seem to be sensitive indicators of krill availability (Waluda et al 2012) while mackerel icefish are both a harvested species and an important alternative prey that buffers some penguins and seals through krill shortages (Hill et al 2005). It is appropriate to present unaggregated results for the most important components (deYoung et al 2004;Hill et al 2006).…”

Section: S Hillmentioning

confidence: 99%

From strategic ambiguity to technical reference points in the Antarctic krill fishery: the worst journey in the world?

Hill

2013

Envir. Conserv.

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SUMMARYThe goals of ecosystem based management (EBM) are strategically ambiguous, meaning that they require interpretation to identify objectives for ecosystem state. Ecosystem states that are useful for achieving such objectives are known as reference points. Soft reference points specify both a state and a probability of the ecosystem being in that state. They are used with simulation models to identify management measures for which the risk of the ecosystem entering an undesirable state is below a specified level. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is responsible for the EBM of Antarctic krill fisheries. CCAMLR used soft reference points for the krill stock in the Scotia Sea and southern Drake Passage to set a regional catch limit. However, this catch limit needs spatial subdivision to protect predators from localized depletion. Modelbased evaluations of different options for subdividing the catch limit used illustrative reference points to assess the depletion risk to multiple predators. This study demonstrates that the apparent risk is sensitive to the choice of reference point and method for aggregating modelled predators. EBM practitioners and stakeholders need to be aware that these factors could therefore bias comparisons of management measures. Nonetheless, qualitative distinctions between different spatial subdivision options are relatively consistent except at high levels of aggregation and extreme reference points. This study also demonstrates a lack of generality in the relationship between current and future ecosystem state. Thus, the EBM goal of maintaining ecosystem resilience implies different reference points for the current state of different ecosystem components. Despite early progress in defining soft reference points for the krill stock, CCAMLR has not yet defined reference points for krill predators. Structured dialogue aimed at identifying collective objectives * Correspondence: Dr Simeon Hill e-mail: sih@bas.ac.uk The online version of this article is published within an Open Access environment subject to the conditions of the Creative Commons Attribution-NonCommercial-ShareAlike licence . The written permission of Cambridge University Press must be obtained for commercial re-use. might be necessary to achieve further progress in CCAMLR and other EBM organizations.

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Diet variability and reproductive performance of macaroni penguins Eudyptes chrysolophus at Bird Island, South Georgia

Cited by 38 publications

References 73 publications

Seabird diet changes in northern Hudson Bay, 1981-2013, reflect the availability of schooling prey

Seabird diet changes in northern Hudson Bay, 1981-2013, reflect the availability of schooling prey

Drivers of intrapopulation variation in resource use in a generalist predator, the macaroni penguin

From strategic ambiguity to technical reference points in the Antarctic krill fishery: the worst journey in the world?

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