Competition occurs when individuals are attempting to utilize the same resource. The outcome is a reduced fitness in the competing individuals. Competition can occur between individuals of the same species or between individuals of two different species. When competition occurs between members of the same species, it is called intraspecific competition. In such a case, the competition is more likely to be intense because both individuals have the same resource requirements. Intraspecific competition is of major importance in ecology since it can play a role in mortality and recruitment rates.

When two individuals from different species compete, we say there is interspecific competition. The classic example of interspecific competition is Darwin’s finches. The competition for a limiting resource, in this case food, eventually caused the two species of finches to find their own niche for survival. A niche is the conditions under which an individual is found including the resources it uses (Mackenzie et al 1998). In the case of Darwin’s finches, one population utilized small seeds while the other utilized large seeds in response to competition.