Dietary relationships among Nearctic and Neotropical migratory shorebirds in a key coastal wetland of South America

MARTÍNEZ CURCI N.S.; AZPIROZ AB; ISACCH JP; ELÍAS, R

Virginia

Congreso; VI Western Hemisphere Shorebird Group Meeting; 2015

Virginia Tech

Dietary requirements influence the structure of shorebird assemblages and this information is key for effective management of important shorebird sites. Here, we describe diet and food resource co-use patterns for four migratory shorebirds at Samborombón Bay, Argentina, one of the most important sites for shorebirds in the Western Hemisphere. Birds consumed at least 15 taxa and exhibit dietary flexibility influenced by both season and tidal level. Co-occurring species exhibited complementary differentiation throughout two dimensions (species composition and size) of their trophic niche. The largest species composition differences in diet were observed between Red Knots, which fed mainly on molluscs, and the other three shorebird species that fed mainly on polychaetes. Among polychaete-eaters, species that shared habitat during autumn (Hudsonian Godwit and White-rumped Sandpiper) overlap in terms of preyed taxa but focused on different polychaete sizes. Alternatively, shorebirds that shared habitat during winter (Hudsonian Godwits and Two-banded Plovers) fed mainly on the same small-sizes of polychaetes but exhibited differences in taxonomic diet composition. Our data highlights the importance of a few items as main trophic resources. It also suggests that the co-use of food resources might be a plausible force shaping migratory shorebirds assemblage structure.