Abstract
A literature review showed that most recent conventional dietary studies of Procellariiformes have used otoliths alone to identify fish prey. Using data from a dietary study of Cory’s Shearwaters Calonectris diomedea, based on 673 regurgitates from adult birds, we quantitatively compared the contribution of otoliths and vertebrae for prey identification and quantification. By using otoliths alone, the importance of the main fish prey was greatly underestimated and several species would have been considered completely absent. Therefore, we strongly recommend the combined use of vertebrae, otoliths and other fish remains in order to improve the quality of dietary studies of seabirds.
Zusammenfassung
Proben mit Rückgrat: die Wirbelsäulen von Fischen helfen, verzerrte Interpretationen im Zusammenhang mit Otolithen und Ernährungsstudien bei Seevögeln zu korrigieren
Eine Auswertung der Literatur hat gezeigt, dass bei den neueren, üblichen Untersuchungen an Röhrennasen (Procellariiformes) nur Otolithen verwendet wurden, um die Beute der Vögel zu bestimmen. Anhand einer Studie über die Ernährung von Gelbschnabel-Sturmtauchern (Calonectris diomedea) verglichen wir in einer quantitativen Auswertung von 673 Proben von Erbrochenem adulter Vögel, welchen Beitrag einerseits die Otolithen, andererseits die Wirbelsäulen bei der Bestimmung und Quantifizierung der Beutetiere spielten. Berücksichtigte man nur die Otolithen, wurde die Bedeutung des wichtigsten Beutefisches stark unterschätzt, und einige Fischarten kamen überhaupt nicht vor. Deshalb empfehlen wir dringend, beides, Otolithen und diverse Fisch-Überreste, zu verwenden, um die Aussage-Qualität von Ernährungsstudien an Seevögeln zu verbessern.
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References
Barrett RT, Camphuysen KCJ, Anker-Nilssen T, Chardine JW, Furness RW, Garthe S, Hüppop O, Leopold MF, Montevecchi WA, Veit RA (2007) Diet studies of seabirds: a review and recommendations. ICES J Mar Sci 64:1675–1691
Bowen WD, Iverson SJ (2012) Methods of estimating marine mammal diets: a review of validation experiments and sources of bias and uncertainty. Mar Mamm Sci. doi:10.1111/j.1748-7692.2012.00604.x
Duffy DC, Jackson S (1986) Diet studies of seabirds: a review of methods. Colon Waterbirds 9:1–17
Gales RP (1988) The use of otoliths as indicators of Little Penguin Eudyptula minor diet. Ibis 130:418–426
Granadeiro JP, Silva MA (2000) The use of otoliths and vertebrae in the identification and size-estimation of fish in predator–prey studies. Cybium 24:383–393
Granadeiro JP, Monteiro LR, Furness RW (1998) Diet and feeding ecology of Cory’s shearwater Calonectris diomedea in the Azores, north-east Atlantic. Mar Ecol Prog Ser 166:267–276
Herling C, Culik BM, Hennicke JC (2005) Diet of the Humboldt Penguin (Spheniscus humboldti) in northern and southern Chile. Mar Biol 147:13–25
Johnstone IG, Harris MP, Wanless S, Graves JA (1990) The usefulness of pellets for assessing the diet of adult Shags Phalacrocorax aristotelis. Bird Study 37:5–11
Karnovsky NJ, Hobson KA, Iverson SJ (2012) From lavage to lipids: estimating diets of seabirds. Mar Ecol Prog Ser 451:263–284
Neves VC, Nolf D, Clarke M (2012) Spatio-temporal variation in the diet of Cory’s shearwater Calonectris diomedea in the Azores archipelago, north-east Atlantic. Deep-Sea Res I 70:1–13
Treacy SD, Crawford TW (1981) Retrieval of otoliths and statoliths from gastrointestinal contents and scats of marine mammals. J Wildl Manage 45:990–993
Tuset VM, Lombarte A, Assis CA (2008) Otolith atlas for the western Mediterranean, north and central eastern Atlantic. Sci Mar 72:7–198
Votier SC, Bearhop S, MacCormick A, Ratcliffe N, Furness RW (2003) Assessing the diet of Great Skuas, Catharacta skua, using five different techniques. Polar Biol 26:20–26
Votier SC, Bearhop S, Witt MJ, Inger R, Thompson D, Newton J (2010) Individual responses of seabirds to commercial fisheries revealed using GPS tracking, stable isotopes and vessel monitoring systems. J Appl Ecol 47:487–497
Whitehead PJP, Bauchot M-L, Hureau J-C, Nielsen J, Tortonese E (1986) Fishes of the North-eastern Atlantic and the Mediterranean. UNESCO, Paris
Wilson RP (1984) An improved stomach pump for Penguins and other seabirds. J Field Ornithol 55:109–112
Zijlstra M, Van Eerden MR (1995) Pellet production and the use of otoliths in determining the diet of Cormorants Phalacrocorax carbo sinensis: trials with captive birds. Ardea 83:123–131
Acknowledgments
Serviço do Parque Natural da Madeira, and in particular Paulo Oliveira, Dília Menezes and Carolina Santos, provided permissions and logistical support to carry out the work at Selvagem Grande. We are grateful to all who gave us valuable help in field work: Maria Dias, Ricardo Rocha, Ana Almeida, Filipe Moniz, Rui Rebelo, Teresa Catry, Ana Sofia Dias and others. We are also grateful for the support provided by the wardens of the Nature Reserve during our stays. This study was financed by Fundação para a Ciência e Tecnologia (FCT-Portugal) through projects PTDC/MAR/71927/2006 and PEst-OE/MAR/UI0331/2011 and through a doctoral fellowship to H. Alonso (BD/47055/2008).
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Communicated by P. H. Becker.
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Alonso, H., Granadeiro, J.P., Ramos, J.A. et al. Use the backbone of your samples: fish vertebrae reduces biases associated with otoliths in seabird diet studies. J Ornithol 154, 883–886 (2013). https://doi.org/10.1007/s10336-013-0970-3
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DOI: https://doi.org/10.1007/s10336-013-0970-3