Competition between closely related species of migratory birds is thought to be important in determining their winter distributions, habitat and resource use. However, the role of active dominance interactions has generally been downplayed. In this paper we review the occurrence of interspecific feeding territories among certain Neotropical migrants. Aggressive dominants have been reported primarily at flowering plants, but also at the honeydew from scale insect infestations, the canopy of insect-rich pioneer trees and, occasionally, fruiting trees. Although the phenomenon is uncommon, aggressively dominant species may be important in certain habitats. The presence of such interspecific territorial systems argues for the poverty of resources in the habitat as a whole. Studying aggressive interactions among migrants is a way of using bird behaviour to define critical resources for conservation management.