Fighting over food unites the birds of North America in a continental dominance hierarchy
The study of aggressive interactions between species usually has been restricted to interactions among small numbers of ecologically close competitors. This article proposes a method for creating a continental-scale hierarchy and reports initial analyses based on this hierarchy. The authors quantified the extent to which a dominance hierarchy of feeder birds was linear, as intransitivities can promote local species’ coexistence. FeederWatchers collected data with which to create a continent-spanning interspecific dominance hierarchy that included species that do not currently have overlapping geographic distributions. Overall, the hierarchy was nearly linear, and largely predicted by body mass, although there were clade-specific deviations from the average mass-dominance relationship. Most of the small number of intransitive relationships in the hierarchy were based on small samples of observations. Few observations were made of interactions between close relatives and ecological competitors like Melanerpes woodpeckers and chickadees, as such species often have only marginally overlapping geographic distributions. Yet, these species’ ranks–emergent properties of the interaction network–were usually in agreement with published literature on dominance relationships between them.
The article was written by Eliot T. Miller, David N. Bonter, Charles Eldermire, Benjamin G. Freeman, Emma I. Greig, Luke J. Harmon, Curtis Lisle, and Wesley M. Hochachka. It appears in BioRxiv, an online science news service. The BioRxiv article was reported on in Science magazine.