Assessing the trophic niche of South American Terns integrating conventional and isotopic approaches

GATTO, A.; YORIO, P.

EMU

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2016 vol. 116 p. 230 - 240

0158-4197

Conventionaldiet studies combined with stable isotope analysis allowed the characterizationof the trophic nicheof South American Terns (Sterna hirundinacea) breeding in Argentina. Direct observation of preydeliveries during mate and chick provisioningshowed that the diet ofSouthAmerican Tern comprised at least 18 prey items, mainly pelagic schooling fish followedby marine invertebrates. Argentine AnchovyEngraulisanchoitawas the main fish prey.Adults delivereda higher proportion of fish and smaller preyto their chicks than mates. Analysis of stable isotope ratios in blood samplesusing Bayesian stable isotope mixing models indicated that adult terns used ahigher proportion of marine invertebrates for self-feeding than for both mateand chick provisioning. Analyses of stable isotopes ratios in chick blood sampleswere consistent with diet determined through direct observations, and indicateddifferences from adults in both the preycontribution to the diet and trophicniche. In addition, isotopic niche analysis showed that chicks presented asignificantly higher trophic position compared to those of self-feeding adults duringboth mate provisioning and chick stages. Results highlight the importance of combiningstable isotope and conventional methods to adequately assess the population?sfood requirements during the breeding season..