Some birds fail to provide parental care or build nests for their babies. Instead, they lay eggs in the nests of other birds. Such birds, known as brood parasites, include cuckoos, honeyguides and cowbirds. Brood parasites tend to have shorter incubation periods and to lay eggs in the nests of smaller birds to give their young the competitive survival advantage. The offspring of parasite birds learn to behaviorally adapt by threatening the host bird's offspring. The brood parasite baby grows faster and bigger, and begs louder and longer for food than its nest mates --- exploiting the host parents' inclination to feed the largest baby bird in the nest, or the one that reaches the highest. Brood parasite offspring starve their foster siblings to death by pushing them out of the nest and vying for all available food.
From the moment they are born, baby birds have to adapt to their surroundings to survive and thrive. Birds adapt both behaviorally and structurally to overcome predators and environmental factors. Behavioral adaptation occurs quite fast in the growth process, and it equips birds with the desired life skills. Though behavioral adaptation occurs in all birds, most bird species display different behavioral adaptation techniques.
Imprinting is a vital and irreversible learning phase that takes place when birds are between seven and fourteen days old. During imprinting, baby birds gain a sense of identification with their species. Imprinting guides the bird in the development of species-directed behavior, such as courtship and mating. Therefore, it is important for the bird to experience a normal and natural imprinting process. Baby birds that are raised by humans become imprinted on humans. For instance, baby parrots raised domestically tend to mimic human speech during their weaning period. A bird that is solely raised by humans lacks the skills to survive on its own in the wild, despite the fact that it is able to fly.
In the wild, when birds are born in a clutch of eight, generally only four survive to the fledgling stage. This is because of competition for food, where babies that produce the loudest and longest calls receive the most food from their mother. For instance, weaver bird chicks modify the length, pitch and amplitude of their begging calls, by accentuating it with trills and short whistles. The hungrier the bird, the more unique its begging call. Additionally, older baby birds force smaller siblings out of the way and prevent them from receiving food.
Flocking for Protection
Baby birds make behavioral adaptations to protect themselves from harsh environmental conditions and predators. Parrotlets are born bereft of any protection, except for a very thin covering of sparse down. To insulate themselves from the cold and keep warm, parrotlet babies huddle together by piling on top of one another --- with the smallest at the bottom and the largest at the top. Shorebird and penguin babies learn from their parents to huddle together to stay warm, thereby increasing their chances of survival into the next season