Digestive Capacity and Toxicity Cause Mixed Diets in Red Knots That Maximize Energy Intake Rate

Among energy-maximizing animals, preferences for different prey can be explained by ranking the prey according to their energetic content. However, diet choice also depends on characteristics of the predator, such as the need to ingest necessary nutrients and the constraints imposed by digestion and...

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Bibliographic Details
Published in:The American naturalist 2014-05, Vol.183 (5), p.650-659
Main Authors: Oudman, Thomas, Onrust, Jeroen, de Fouw, Jimmy, Spaans, Bernard, Piersma, Theunis, van Gils, Jan A.
Format: Article
Language:English
Subjects:
Animal digestion
Animal Shells
Animals
Bacteria
Bacterial Toxins
Birds
Bivalvia
Calidris canutus canutus
Charadriiformes - physiology
Diet
Digestive System Physiological Phenomena
Dosinia
Energy intake
Experimentation
Fresh water
Gastropoda
Linear programming
Loripes lucinalis
Mauritania
Mollusks
Predation
Predatory Behavior
Salinity
Sea water
Toxicity
Toxins
Water consumption
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Summary:Among energy-maximizing animals, preferences for different prey can be explained by ranking the prey according to their energetic content. However, diet choice also depends on characteristics of the predator, such as the need to ingest necessary nutrients and the constraints imposed by digestion and toxins in food. In combination, these factors can lead to mixed diets in which the energetically most profitable food is not eaten exclusively even when it is abundant. We studied diet choice in red knots (Calidris canutus canutus) feeding on mollusks at a West African wintering site. At this site, the birds fed primarily on two species of bivalves, a thick-shelled one (Dosinia isocardia) that imposed a digestive constraint and a thin-shelled one (Loripes lucinalis) that imposed a toxin constraint. The latter species is toxic due to its symbiotic association with sulfide-oxidizing bacteria. We estimated experimentally the parameters of a linear programming model that includes both digestive and toxin constraints, leading to the prediction that red knots should eat a mixture of both mollusk species to maximize energy intake. The model correctly predicted the preferences of the captive birds, which depended on the digestive quality and toxicity of their previous diet. At our study site, energy-maximizing red knots appear to select a mixed diet as a result of the simultaneous effects of digestive and toxin constraints.
ISSN:0003-0147
1537-5323
DOI:10.1086/675759