Every species must find a way to make a living in the ecosystem. All organisms need two basic resources, living space and food. Only when both are abundant can organisms avoid competition. In cases where individuals share exactly the same niche, life becomes a zero-sum game.
Competition pervades nature, but only occasionally does it take the form of direct competition.
From the evolutionary perspective, avoiding conflict makes sense because competition imposes costs. Consequently, individuals able to avoid conflicts with their species-mates tend to reproduce more successfully. For the last 25 years, Jared Diamond has researched the lifeways of New Guinea's 513 bird species. He has found several bird species, all descended from a common ancestor, that now live in strictly separate altitude zones. When two species did not subdivide the available living space, Diamond found that they feed at different times of the day.