MEPS 563:219-232 (2017)  -  DOI: https://doi.org/10.3354/meps11979

Invisible trophic links? Quantifying the importance of non-standard food sources for key intertidal avian predators in the Eastern Atlantic

Pedro M. Lourenço1,*, Teresa Catry1, Ricardo J. Lopes2, Theunis Piersma3,4, José P. Granadeiro1

1Centro de Estudos do Ambiente e do Mar (CESAM), Departamento de Biologia Animal, Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal
2Centro de Investigação em Biodiversidade e Recursos Genéticos (CIBIO), InBIO Laboratório Associado, Universidade do Porto, 4485-661 Vairão, Portugal
3NIOZ Royal Netherlands Institute for Sea Research, Department of Coastal Systems, and Utrecht University, PO Box 59, 1790 AB Den Burg, Texel, The Netherlands
4Chair in Global Flyway Ecology, Conservation Ecology Group, Groningen Institute for Evolutionary Life Sciences (GELIFES), University of Groningen, PO Box 11103, 9700 CC Groningen, The Netherlands
*Corresponding author:

ABSTRACT: Coastal wetlands are heterogeneous systems with multiple inputs and complex interactions within local food webs. Interpreting such complexity is limited by incomplete knowledge of trophic interactions among organisms. Although widely recognized as secondary consumers and predators of intertidal macroinvertebrates, shorebirds can also consume lower-trophic-level food sources, and frequently forage in adjacent supratidal habitats. To ascertain potential trophic links between overwintering shorebirds and alternative non-standard food sources, we collected carbon and nitrogen stable isotope data of shorebirds and benthic organisms from 4 coastal wetlands along the Eastern Atlantic: Tejo Estuary, Portugal; Sidi-Moussa, Morocco; Banc d’Arguin, Mauritania; and Bijagós Archipelago, Guinea-Bissau. Using dual-isotope Bayesian mixing models, we evaluated the relative importance of intertidal benthic macroinvertebrates and 3 other potential food sources (biofilm and seagrass rhizomes from intertidal areas, and saltpan macroinvertebrates) in the diet of wintering shorebirds. Although intertidal macroinvertebrates form the main part of most shorebird species’ diet, our data revealed that supratidal saltpans can contribute to >30% of the biomass ingested by several shorebird species. Seagrass rhizomes represented >10% of the diet of several species in Banc d’Arguin and in Sidi Moussa. Little stint Calidris minuta appears to consume biofilm on all 3 wetlands where they were sampled, which is the first time biofilm consumption by shorebirds has been detected along the East Atlantic Flyway. Empirical evidence for generalized consumption of alternative food sources by intertidal avian predators show the greater complexity and food web connectivity in and of intertidal habitats, and also with the surrounding habitats.


KEY WORDS: Shorebird · Diet · Macroinvertebrate · Biofilm · Saltpan · Seagrass · Wetland


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Cite this article as: Lourenço PM, Catry T, Lopes RJ, Piersma T, Granadeiro JP (2017) Invisible trophic links? Quantifying the importance of non-standard food sources for key intertidal avian predators in the Eastern Atlantic. Mar Ecol Prog Ser 563:219-232. https://doi.org/10.3354/meps11979

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