Heterospecific Dominance Hierarchy in Roosting Site Selection at a Shared Nest Resource

The resources needed by different species are fundamental for allowing multiple species to coexist. However, when species share resources, competition is expected to occur with associated costs. Sociable weavers (Philetairus socius) build large communal nests that provide, among other resources, nesting chambers that provide shelter, protection, thermal buffering and insulation for roosting birds of other species. We consider the interactions of heterospecifics roosting in colonies to determine if species select chambers due to their insulation properties, if there is a dominance hierarchy in acquiring chambers, and/or if novel behaviours to access chambers are employed. Our study demonstrates that different species use different aspects of the nest resource, preferring roosting chambers depending on the location of the chamber within the colony. To access this resource, we show that aggressive interactions occur between the species, resulting in a dominance hierarchy with size being positively related to the dominance of a species. Furthermore, our data show temporal separation in timing of arrival at the chambers, with smaller species tending to arrive later and occupy vacant chambers, thus avoiding aggressive interactions with more dominant heterospecifics. Therefore, adapting to competition, multiple species use novel behaviours and interactions, allowing them to coexist at this same engineered resource.