Diet composition of the White-rumped Sandpiper and the Baird's Sandpiper in Patagonia, Argentina

HEVIA GD; CAPASSO S; DIAZ JI; D'AMICO VL

Workum

Conferencia; International Wader Study Group Annual Conference; 2018

International Wader Study Group

Migratory shorebird species from the Western Hemisphere like the White-rumped Sandpiper (WRSA) and the Baird´s Sandpiper (BASA) have their non-breeding areas in southern South America. Here, we describe the diet composition of WRSA and BASA collected both in coastal and inland sites from Patagonia, Argentina. A total of 26 WRSA and 38 BASA stomach content samples were obtained from dead birds collected in January between 2004 and 2006. Preys were collected, identified and quantified under an optical microscope. The index of relative importance (IRI) was used to establish the contribution of each prey category. Trophic diversity was calculated using Brillouin´s formula (HB), and the niche trophic scope was calculated with the Levins index (B). Trophic spectrum based on 1158 preys comprised 25 taxonomic entities. Both species consumed seeds, insects (mostly Coleoptera and Diptera), Mollusca, and as minor contributor, Amphipoda and Isopoda crustaceans, although in different proportions. The HB in each stomach ranked between 0-1.49 (BASA) and 0-0.9 (WRSA). The mean diversity was 1.24 (BASA) and 0.9 (WRSA). The extent of the trophic niche B was 1.95 (BASA) and 1.59 (WRSA). Besides, HB and B extent were greater in inland environments than in coastal environments (HBcoastal= 0.65 vs. HBinland= 1.66; Bcoastal =1.34 vs. Binland= 3.14).Birds showed no preference for any prey category based on the IRI. Although seeds and insects were the most abundant items in the stomach of both shorebird species, BASA presented a higher diversity of dipterans (i.e., Chironomidae, Ceratopogonidae, among others). Cladocera and Decapoda crustaceans were only presented in WRSA diet. Diet diversity was slightly higher in BASA, suggesting a more generalist and broader trophic niche.