Journal ArticleDOI
Assessing the diet of great skuas, Catharacta skua, using five different techniques
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This study assessed the diet of great skuas using five techniques (pellets, prey remains, spontaneous regurgitates, observed feeds and water off-loading), and found that estimates of diet derived from each sampling technique during a single breeding season were generally similar.Abstract:
Several different techniques have been used to study the diet composition of skuas and gulls in polar regions. In this study, we assessed the diet of great skuas using five techniques (pellets, prey remains, spontaneous regurgitates, observed feeds and water off-loading). The estimates of diet derived from each sampling technique during a single breeding season were generally similar. Although it is easy to collect large samples of pellets and remains, these over-estimate the amount of indigestible material in the diet. Prey remains provide a high degree of taxonomic accuracy, but may under-estimate prey swallowed whole. Water off-loading provides unbiased estimates of chick diet but only during a short period in the breeding season. It may also stress birds, and is labour-intensive. Spontaneous regurgitates are useful for assessing chick and adult diet but are difficult to collect systematically, and differing prey digestibility may bias results. Observed feeds are time consuming to record and over-represent easily identifiable prey. Technique-dependent biases highlight that sampling methods should be selected on the basis of sample sizes, time, taxonomic detail and age of study birds. Biomass may be estimated using pellets with correction factors, and also spontaneous regurgitates and water off-loading, but prey remains and observed feeds may be more inaccurate.read more
Citations
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Journal ArticleDOI
Applying stable isotopes to examine food‐web structure: an overview of analytical tools
Craig A. Layman,Márcio S. Araújo,Ross E. Boucek,Caroline M. Hammerschlag-Peyer,Elizabeth Harrison,Zachary R. Jud,Philip Matich,Adam E. Rosenblatt,Jeremy J. Vaudo,Lauren A. Yeager,David M. Post,Stuart Bearhop +11 more
TL;DR: A comprehensive review of stable isotope analysis techniques, and a set of suggestions that transcend individual analytical approaches, are provided to help identify the most useful approaches to apply to a given data set.
Journal ArticleDOI
Best practices for use of stable isotope mixing models in food-web studies
Donald L. Phillips,Richard Inger,Stuart Bearhop,Andrew L. Jackson,Jonathan W. Moore,Andrew C. Parnell,Brice X. Semmens,Eric J. Ward +7 more
TL;DR: Stable isotope mixing models are increasingly used to quantify consumer diets, but may be misused and misinter- preted, and major challenges to their effective application are addressed.
Journal ArticleDOI
Diet studies of seabirds: a review and recommendations
Robert T. Barrett,Kees Camphuysen,Tycho Anker-Nilssen,John W. Chardine,Robert W. Furness,Stefan Garthe,Ommo Hüppop,M.F. Leopold,William A. Montevecchi,Richard R. Veit +9 more
TL;DR: To enhance comparability of findings among studies, species, and oceanographic regions, a recommendation on standards for the reporting of results in the literature is made.
Journal ArticleDOI
Changes in fisheries discard rates and seabird communities
Stephen C. Votier,Robert W. Furness,Stuart Bearhop,Stuart Bearhop,Jonathan E. Crane,Richard W. G. Caldow,Paulo Catry,Kenny Ensor,Keith C. Hamer,Anne V. Hudson,Ellen Kalmbach,Nicholas Klomp,Simone Pfeiffer,Simone Pfeiffer,Richard A. Phillips,Isabel Prieto,David R. Thompson +16 more
TL;DR: Reduced rates of discarding, particularly when coupled with reduced availability of small shoaling pelagic fish such as sandeel, result in an increase in predation by great skuas on other birds.
Journal ArticleDOI
Individual responses of seabirds to commercial fisheries revealed using GPS tracking, stable isotopes and vessel monitoring systems
Stephen C. Votier,Stuart Bearhop,Matthew J. Witt,Richard Inger,David R. Thompson,Jason Newton +5 more
TL;DR: The influence of commercial fisheries’ activity on the foraging behaviour of individual breeding northern gannets Morus bassanus is assessed and intra-population differences in discard consumption by gannet at-sea behaviour are revealed; differences that have impacts on foraging effort and body condition.
References
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Book
Practical Statistics for Field Biology
TL;DR: This chapter discusses measurement and Sampling concepts, measurement practice, and the Basis of Statistical Testing as well as measuring Variability, Probability, and Correlations.
Journal ArticleDOI
Diet Studies of Seabirds: A Review of Methods
David C. Duffy,Susan Jackson +1 more
TL;DR: Methods of collecting, analysing and presenting data on the diets of seabirds are reviewed, with consideration of methods employed in diet studies of other organisms.
Journal ArticleDOI
On the Feeding Ecology of the Herring Gull Larus argentatus Pont. in the Northern Part of the Netherlands
Journal ArticleDOI
The effects of changes in food availability on the breeding ecology of great skuas Catharacta skua in Shetland
TL;DR: Changes in the age structure of the breeding population and the absence in 1989 of 28% of adults colour-ringed during incubation in 1988 suggest an increase in the rate of egress since the 1970s, which probably represents an increased in the long-term costs of reproduction to adults at this colony.