Character displacement in shorebirds

Abstract

Modification of phenotypic traits induced by character displacements allow species to coexist by reducing interspecific competition. This study explores if and how shorebirds partition feeding ressources by foraging at different water depths outside the breeding season. During this period, communities of up to dozen shorebird species coexist on suitable habitats at land-water interfaces. By video recording 22 species of migrating and wintering shorebirds in different sites, we show that their distribution according to the water height at which they forage is not random but follows a gradient of increasing water height according to increasing species body size. Species-specific beak and tarsus lengths are positively correlated with the water height at which the different species forage. Our data do not support a trade-off in investment between beak length and tarsus length in our study species set. Congeneric species that are expected to be morphologically and ecologically more similar forage at contrasted water heights. Altogether, our findings supports the idea of resource partitioning, and consequently of competition relaxation, by morphological and/or by behavioral character displacements.