Natality and Mortality
In a population which has reached an equilibrium size, abundance is independent of birth and death rates. For species in equilihrium. then, a study of birth and death rates is not necessary to understand the control of the equilibrium abundance. However, as Darwin (1859) said, "A large number of eggs is of some importance to those species which depend upon a fluctuating amount of food, for it allows them rapidly to increase in numbers.