Predation on the southwestern atlantic fiddler crab (Uca uruguayensis) by migratory shorebirds (Pluvialis dominica, P. squatarola, Arenaria interpres, and Numenius phaeopus)

Abstract

In Bahia Samborombon (SW Atlantic; 35°30'-36°22'S; 56°45'-57°23'W) migratory American golden plover (Pluvialis dominica), black-billed plover (P. squatarola), ruddy turnstone (Arenaria interpres), and whimbrel (Numenius phaeopus) forage on fiddler crabs (Uca uruguayensis). These shorebirds have distinct patterns of feeding behavior and capture different proportions of each sex and size. P. dominica made short runs, capturing mostly juvenile crabs, which are eaten whole. P. squatarola use a similar feeding strategy but capture females primarily. A. interpres walks continuously, capturing almost exclusively large male crabs (71%). N. phaeopus walk in the Uca patch and probe burrows by inserting the bill; they primarily capture females. The feeding rate of A. interpres is higher than that of P. dominica, P. squatarola, and N. phaeopus. Handling time shown by P. dominica and A. interpres was greater than the other two species for all categories of crabs. In all cases, handling time of male Crabs was greater than those of either females or juveniles. All the evidences suggest that U. uruguayensis is an important food source for all these species and should be accounted in any conservation endeavor.