The Scarlet Macaw nests in large holes in tall living or dead trees; they do not dig these holes, but rely on finding cavities that are high off the ground and have vertical entrances. Finding enough of such trees can be a limiting factor for these birds to maintain populations in an area, especially because some bee species occupy the same kind of tree cavity. A macaw pair will lay 1-2 eggs per season in such a nest and raise them together. These macaws are serially monogamous, but they may change mates after several seasons.
In 1900, these parrots could still be seen in forests throughout Costa Rica; by 1950, however, due to habitat destruction, they were absent from the Caribbean slope except in the Northwest. They have also suffered from the pet trade; fortunately, today they are protected in every country in which they live. However, in Costa Rica, their populations still have been reduced by the destruction of their habitat. They are now constrained to the forests of the upper Golfo de Nicoya, such as in Palo Verde National Park, and the forests of the Osa Peninsula, such as at Corcovado National Park.