Density Dependent Factors - Population Regulation
The density dependent factors are intrinsic or biotic factors and they depend on interactions between individuals within same population or populations of different species. Density dependent factors may stabilise the population at the level determined by carrying capacity of the environment. The important density dependent factors are reproductivity, emmigration, competition for resources, predation, parasites, and diseases. The contribution of these factors may vary from species to species.
In large populations the number of offsprings produced are less, thus self-regulating the population size. You have also read how emmigration of individuals from a population reduces its density. Competition can be between individuals of same species called intra specific competition and between individuals of different species called inter specific competition. Generally, members of the same species need same resources and are bound to compete for them. In some bird species males and females have different beak lengths enabling them to feed on different insect prey.