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Factors influencing food-load sizes brought in by Shags Phalacrocorax aristotelis during chick rearing

Wanless, S.; Harris, M. P.; Russel, A. F.. 1993 Factors influencing food-load sizes brought in by Shags Phalacrocorax aristotelis during chick rearing. Ibis, 135 (1). 19-24. 10.1111/j.1474-919X.1993.tb02805.x

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Abstract/Summary

Weights of food loads brought back to the colony by 26 Shags Phalacrocorax aristotelis rearing chicks were determined using the water-offloading procedure. Loads consisted almost entirely of lesser sandeels Ammodytes marinus. Load size was extremely variable, ranging from 8 to 208 g with a mean load weight of 106 g. Data on foraging behaviour collected concurrently demonstrated that Shags brought back heavier loads when they were feeding farther away from the colony and when brood biomass was larger. These two variables together explained 70.3% of the variation in load size. We postulate that adults had already digested their own food requirements by the time they arrived back at the nest, and the contents of the loads were therefore primarily for the young. On 67% of trips, Shags caught, on average, more than one fish per dive. This estimate ignores the food requirements of the adult, and therefore true prey-capture rates must have been higher.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1111/j.1474-919X.1993.tb02805.x
Programmes: CEH Programmes pre-2009 publications > Other
CEH Sections: _ Pre-2000 sections
ISSN: 0019-1019
Additional Keywords: Isle of May, Shags, Phalacrocorax aristotelis
NORA Subject Terms: Zoology
Date made live: 10 Oct 2008 11:04
URI: http://nora.nerc.ac.uk/id/eprint/4516

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