Parakeet is a generic term for small parrots with long tails, but the budgerigar bird (or budgie) hails from the Australian Outback and is what most people think of when they mention parakeets. The Outback is a vast and arid wilderness composed of deserts, swamps, inlets and other forbidding biomes where many species of animals compete and coexist.
Parakeets cope with the dry conditions of the Outback by getting food from the fruit and grass seeds that constitute their diet. They can go for enormous lengths of time without actually drinking any water due to a long legacy of adaptations to the Outback's demands.
The birds are nomadic in their feeding and breeding habits. They follow the rains that infrequently fall on the Outback's vast plains, then descend to consume whatever grass and grass seed they can find. Normally they travel in small flocks but extreme conditions can drive flocks together into massive migrations comprising thousands of birds.
Budgies breed voraciously in the wake of rainfall after long periods of drought. Their young hatch and fledge so quickly that the parent parakeets might lay multiple times in a single nest within the space of a few short months, creating a sizable population boom.