Abstract
We examined the effect of prey type, repeated stomach flushing, digestion time, and meal size on the assessment of dietary intake of captive adult Cory’s shearwaters (Calonectris diomedea). For each of Cory’s shearwaters’ main prey type (fish, cephalopod, and crustacea), we used three different meal sizes and four digestion times, stomach-flushing the birds 1, 4, 8, or 16 h after feeding. On average, fish and cephalopods showed similar percentages of mass recovery (between 23% and 33%), whereas crustaceans showed a recovery about 10–15% greater. Conversely, fish and crustaceans showed similar percentages of items recovered (between 52% and 77%), whereas cephalopods showed about 10–35% greater recovery rates. We found no significant differences in the percentage of individual prey items recovered and the interval between ingestion and recovery, over intervals ranging from 1 to 16 h.
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Acknowledgements
We thank Ana Mendes, Ana Paixão, and Maria Carvalho for their valuable assistance conducting the experiment; Cédric d’Udeken d’Acoz for kindly identifying the crustacean; Prof. Malcolm Clarke and Dr. David Álvarez for their criticism and useful comments on an earlier version of the manuscript and for identifying the squid; and J. González-Solís and an anonymous referee for comments on the manuscript. This study was funded by the Portuguese Foundation for Science and Technology (grant PRAXIS XXI/BIC/17094/98 to V.C.N. and research contract PRAXIS/2/2.1/MAR/1680/95). The experiment performed in this study complies with Portuguese law and was conducted under licence number 1/98 issued by Direcção Regional do Ambiente.
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Communicated by F. Bairlein.
L.R. Monteiro was tragically killed in a plane crash in the Azores in December 1999.
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Neves, V.C., Bolton, M. & Monteiro, L.R. Validation of the water offloading technique for diet assessment: an experimental study with Cory’s shearwaters (Calonectris diomedea). J Ornithol 147, 474–478 (2006). https://doi.org/10.1007/s10336-005-0040-6
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DOI: https://doi.org/10.1007/s10336-005-0040-6