MEPS 479:203-221 (2013)  -  DOI:

Combined spatial and tidal processes identify links between pelagic prey species and seabirds

S. L. Cox1,2,*, B. E. Scott1, C. J. Camphuysen3

1School of Biological Sciences, Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK
2School of Marine Science and Engineering (Faculty of Science and Technology), Plymouth University, Drake Circus, Plymouth PL4 8AA, UK
3Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands

ABSTRACT: To gain further insight into the foraging behaviour of predator species, it is essential that interactions between predators, their prey and the surrounding environment are better understood. The primary purpose of this study was to determine the underlying processes, both physical and biological, driving variation in the times and locations of seabird foraging events. Using fine-scale simultaneous measurements of seabird abundance, prey density and oceanographic variability collected during an at-sea survey in the Firth of Forth region of the North Sea, zero-inflated negative binomial models were applied to identify the underlying processes driving foraging behaviour in 2 seabird species: the common guillemot Uria aalge and the black-legged kittiwake Rissa tridactyla. Both guillemot and kittiwake models showed consistency in their results; specific tidal states and thermal stratification levels explained observed increases in abundance. The secondary purpose of this study was to identify key oceanographic processes driving variability in prey density and determine if these were comparable to those underlying the behaviour of foraging seabirds. Log-transformations of 2 measures of prey density, NASC-40-50MAX and NASC-50-70MAX, were modelled using generalised least squares. Similar tidal conditions and thermal stratification levels explained distributional patterns, suggesting that these processes act to increase prey availability, creating profitable foraging opportunities for predators to exploit. This has been termed the tidal coupling hypothesis and identifies that critical marine habitats occur not only at limited spatial locations but also within specific temporal intervals relating to the tidal cycle. Furthermore, by incorporating this oceanographic influence on foraging habitat, fine-scale predator–prey relationships were also identified. Foraging guillemots and kittiwakes displayed a Type II functional response to increasing values of NASC-40-50MAX.

KEY WORDS: Predator-prey interaction · Physical-biological coupling · Spatio-temporal variability · Foraging ecology · Critical marine habitat · Trophic relationship

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Cite this article as: Cox SL, Scott BE, Camphuysen CJ (2013) Combined spatial and tidal processes identify links between pelagic prey species and seabirds. Mar Ecol Prog Ser 479:203-221.

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