Competition in biology is the process of interaction between two or more organisms, which are using the same resources e.g food, space, mate or occupying the same ecological niche. Competition between organisms often result in one or bother organisms getting harmed due to the strive for a limited resource.
Hence, in the case of two warblers occupying the same habitat and feeding on the same prey, competition is inevitable between these two species of organism. Therefore, the competition will eventually cause one of the species to be eliminated or killed.