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8 - Biophysical influences on seabird trophic assessments
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- By W. A. Montevecchi, Cognitive and Behavioural Ecology Program, Memorial University St John's, Newfoundland, Canada A1B 3X9, S. Garthe, Centre for Research and Technology Westkuste, University of Kiel Hafentörn, D-25761 Büsum, Germany, G. K. Davoren, Zoology Department, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2
- Edited by I. L. Boyd, University of St Andrews, Scotland, S. Wanless, NERC Centre for Ecology and Hydrology, UK
- C. J. Camphuysen, Royal Netherlands Institute for Sea Research
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- Book:
- Top Predators in Marine Ecosystems
- Published online:
- 31 July 2009
- Print publication:
- 11 May 2006, pp 118-130
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- Chapter
- Export citation
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Summary
The foraging behaviour and ecology of top predators are expressions of trophic and ecosystem dynamics. Oceanographic fluctuations as well as biological interactions affect exothermic species and, through them, influence their endothermic predators. Planktivorous and piscivorous, surface-feeding and diving seabirds exhibit varying constraint, flexibility, specialization and opportunism in their responses to prey and environmental conditions. Responses can be direct in terms of foraging behaviour, prey capture and diet; or indirect in terms of egg and chick production, growth, breeding success, recruitment and population change. Protracted indirect effects lag behind and buffer environmental change with behaviour and life-history attributes. Focal forage species that fuel large vertebrate food webs exhibit extreme fluctuations in abundance, being highly sensitive to biophysical perturbations, including fishing. Changes in their biology often shift ecosystems to alternative states, yet forage species are understudied. Indications about forage species derived from seabirds can be broadly informative. Synoptic meso-scale studies that link colony measurements to vessel surveys of prey and predators within avian foraging ranges provide an approach for assessing predator responses to variation in prey fields and oceanography. Tracking free-ranging foragers with animal-borne data loggers (which record temperature, pressure, activity and position) details behavioural solutions to current conditions. These foraging tactics of individual predators are mechanisms of the social and population responses that we measure, estimate and model. Physical data from loggers, vessels and satellites can be combined to define thermal habitats and ‘hotspots’ used by predators and prey.