Density and spatial distribution of migratory shorebirds in different foraging habitats in the coastal region of Piauí State, Brazil

Abstract

Coastal habitats are important feeding grounds for migratory shorebirds, which turns the coast of Piauí State into an important region for birds’ migration cycle. This study aimed to identify migratory shorebirds, analyze their patterns of habitat preference on coastal Piauí State, Brazil, and identify classes of invertebrates found in foraging sites. In total, 23,829 records of migratory shorebirds belonging to 15 species were found at feeding sites, presenting significant segregation between different foraging substrates (F1,23 = 8.41; p = 0.001). Limnodromus griseus (56.5±98.42; p > 0.001), Numenius hudsonicus (35.96±37.37; p > 0.001), and Calidris canutus (34.4±80.84; p < 0. 001) were the species accounting for the highest densities in muddy substrate. Calidris pusilla (77.37±178.02; p > 0.001), Charadrius semipalmatus (66±142.17: p > 0.001), and Calidris alba (56.5±181.24; p > 0.001) were the most significant species in sandy-muddy substrate. Birds’ lowest density was observed in sandy habitat, but C. alba (22.41±40.9) recorded the highest density in this substrate. Overall, most shorebirds (92.8 %) preferred foraging substrates presenting higher concentration of fine particles (silt, clay, and fine sand). Invertebrates belonging to classes Polychaeta, Gastropoda, Bivalvia, and Malacostraca prevailed in these sites. Therefore, substrate type and prey composition are factors influencing the density of migratory shorebirds in foraging sites. In addition, this region witnesses the occurrence of endangered species, and it reinforces the importance of these feeding sites for them during their migration to Brazil’s coastal region.