Cormoran Phalacrocorax Olivaceus

J Ornithol
DOI 10.1007/s10336-012-0863-x

ORIGINAL ARTICLE

Trophic position of the Neotropic Cormorant (Phalacrocorax
brasilianus): integrating diet and stable isotope analysis
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˜
Jorge Munoz-Gil • Gedio Marın-Espinoza •
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Jose Andrade-Vigo • Roseline Zavala • Astolfo Mata

Received: 20 September 2011 / Revised: 12 March 2012 / Accepted: 21 May 2012
Ó Dt.Ornithologen-Gesellschaft e.V. 2012

Abstract Stable isotope analysis has been extensively
used to establish trophic relationships within avian communities of marine ecosystems. The Neotropic Cormorant
(Phalacrocorax brasilianus) is a good representative of
marine bird communities along the northern coasts of
South America. The diet and trophic position of the Neotropic Cormorant during the non-breeding seasonin a
tropical lagoon, Bocaripo-Chacopata, in northeastern
Venezuela, was determined by using gut content analyses
and stable isotope ratios of carbon (d13C) and nitrogen
(d15N), from birds, fish and invertebrates muscle tissue.
Gut content and stable isotopes both indicated that cormorants are strict piscivores, whose diet is mainly based
on benthonic fish, and thus occupy a high trophiclevel,
above that of the piscivorous fish in the same habitat.
Crustaceans and mollusks were circumstantial components

of cormorant diet, found in the gut of some cormorant fish
prey, as shown from their d15N isotope values. A mixing
model, MixSIR, estimated that two fish species, Cetengraulis edentulous and Arius sp., were the main components
of the diet. However, consumer stable isotopevalues fell
outside the mixing polygon, suggesting that either another
food source with a larger 15N value was present in the diet
of the cormorant but we failed to detect it, or, that we used
inaccurate discrimination factors in the model. This cormorant species is a trophic specialist. It appears that, at
least during the studied period, this population fed only on
fish from the lagoon or fromthe nearby sea.
Keywords Stable isotopes Á Neotropic Cormorant Á
Trophic ecology Á Carbon Á Nitrogen Á Mixing model
Zusammenfassung

Communicated by P. H. Becker.
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Jose Andrade-Vigo: Deceased.
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J. Munoz-Gil
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Centro de Investigaciones Ecologicas Guayacan,
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Universidad de Oriente, Cumana, Sucre, Venezuela
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G. Marın-Espinoza Á J. Andrade-Vigo
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Departamento de Biologıa,Nucleo de Sucre,
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Universidad de Oriente, Cumana, Sucre, Venezuela
R. Zavala
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Departamento de Quımica, Nucleo de Sucre,
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Universidad de Oriente, Cumana, Sucre, Venezuela
A. Mata (&)
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Laboratorio de Biologıa de Organismos, Centro de Ecologıa,
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Instituto Venezolano de Investigaciones Cientıficas (IVIC),
Apdo. 20632, Caracas 1020-A, Venezuela
e-mail: amata@ivic.gob.veDie trophische Stellung der Olivenscharbe (Phalacrocorax brasilianus): Eine Integration von Nahrungs- und
Isotopenanalysen
¨
Die analyse stabiler isotope wird haufig angewendet, um
¨
trophische Zusammenhange in Vogelgemeinschaften
¨
mariner Okosysteme zu untersuchen. Die Olivenscharbe
(Phalacrocorax brasilianus) ist ein geeigneter Vertreter der
¨
¨
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marinen Vogelgemeinschaft dernordlichen Kusten Sudamerikas. Die Nahrung und die trophische Stellung dieses
neotropischen Kormorans wurden außerhalb der Brutsaison
in der tropischen Lagune Bocaripo-Chacopata im Nordos¨
ten Venezuelas durch Darmanalysen und Isotopenverhaltnissen von Kohlenstoff (d13C) und Stickstoff (d15N) in
Vogel-, Fisch-, und Invertebratenmuskelgeweben untersucht. Darminhalte und stabile Isotope weisendiesen
Kormoran als strikten Fischfresser aus, dessen Nahrung

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hauptsachlich aus benthischen Fischen besteht, und der
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damit eine hohe trophische Ebene besetzt, uber jener der
piscivoren Fische des gleichen Habitats. Crustaceen und
¨
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Mollusken sind zufallige Nahrung aus den Darmen mancher Beutefische des Kormorans, ersichtlich aus ihren
d15N-Isotopenwerten. Das...