Ecological segregation and vocal interactions in two sympatric Laterallus crakes

Abstract

Ecological segregation and interspecific territoriality can reduce exploitative competition in morphologically and ecologically very similar species allowing their coexistence. We studied habitat use and features, ecomorphology and homo- and heterospecific playback responses in the similar and sympatric Red-and-white Crake (Laterallus leucopyrrhus) and Rufous-sided Crake (Laterallus melanophaius) on the coast of the Río de la Plata, Argentina. We carried out playback sessions with stimuli of both crakes in four habitat types potentially used by them across the four seasons (coastal humid scrub, bulrush, floodable grassland and exotic yellow iris). Crakes were segregated year-round by habitat, with minor overlap: Red-and-white Crakes used bulrush, while Rufous-sided Crakes used coastal humid scrub. Patterns of habitat use were the same when using homo- or heterospecific playback stimuli, and both species responded similarly to homo- and heterospecific playback trials in their selected habitats. Crakes were morphologically distinct and some of their differences can be related to habitat features and resource exploitation: Red-and-white Crakes had longer tarsi and “blunt” bills and inhabited the deeper and denser bulrush, while Rufous-sided Crakes had shorter tarsi and “dagger” bills and inhabited the shallower and more open coastal humid scrub. Habitat use resulting in spatial segregation in these crakes seems to be more related to specific abilities to exploit different habitats than to interspecific competition or interspecific territoriality. Habitat adaptation would be more relevant within large patches of homogeneous and simple habitats selected by each Crake, while interspecific territoriality would gain importance at habitat boundaries with heterogeneous or intermediate conditions.