The oldest nestling enjoys the major competitive advantage of being fed first at every meal. Its sibling seldom survives. Usually the parents push a dead chick out of the nest. Maneuvering its body out of the nest hole is the first challenge if the hole is quite narrow. Sometimes the parents cut back the nestling's rations to force it to make the effort.
Macaws usually leave their parents and start looking for a mate at age two or three.
Finding a place to lay eggs is a far more difficult matter. A contributing factor in the macaws' low reproduction rate is an acute housing shortage. A square mile of rain forest in Amazonian Peru contains as few as one or two nest sites that are deep, clean, and dry enough for large macaws. Macaws play and interact with each other in ways that most other birds do not. A pair of mated adults will preen each other and their offspring for hours, removing lice and ticks and naturally dispersing body oil on one another's feathers.