The hyacinth macaw nests in holes in trees. The clutch size is two or three eggs, although usually only one fledgling survives. The hyacinth macaw eats seeds, nuts, fruits, and vegetable matter. Eight species of palm are central to its diet. Its exceptionally powerful bill, the largest of its kind in the world, allows it to eat otherwise inaccessible nuts and seeds.
Macaws can eat some poisonous seeds and unripe fruits that no other animal can digest.
Scientists believe this is possible because the birds eat chunks of clay from river banks. The clay is thought to help absorb the poisons or make them harmless. Macaws play an important role in seed dispersal. They are messy eaters, carrying and dropping many nuts and seeds. All 18 species of macaws are threatened.