Great green macaws are the largest parrots in their natural range. They are mainly green in color and have a reddish forehead and pale blue lower back, rump and upper tail feathers. The tail is brownish-red tipped with very pale blue. The bare facial skin is patterned with lines of small dark feathers, which are reddish in older and female parrots. Juveniles have grey-colored eyes instead of black, are duller in color and have shorter tails which are tipped in yellow.
Great green macaws are found in Central and South America ranging from Honduras to western Ecuador. They live in dry tropical forests, evergreen rainforests, and in some areas prefer humid woodlands.
Great green macaws are diurnal and social birds. They are usually seen in pairs or small groups of up to four to eight individuals, very rarely more. In Costa Rica, after the breeding season Great green macaws gather in flocks and migrate towards the coasts in search of food. In Costa Rica, these flocks usually consist of up to 18 birds. Great green macaws are arboreal; they rest and forage in the upper areas of the canopy. These are very noisy birds especially when in flight and their extremely loud, raucous "aak, raak" can be heard at great distances.
Great green macaws are monogamous and form strong pair bonds for life. Their breeding season starts in December and ends in June in Costa Rica, and from August to October in Ecuador. Pairs nest in cavities high up in the trunk, near the crown of the tree. The female lays a clutch of 2-3 eggs and incubates them for 26 days. Chicks hatch weighing 23g, can fly after 12-13 weeks, and are weaned after 18-20 weeks when they weigh over 900g. After fledging juveniles stay with the parents as a family unit for a significant amount of time, only separating gradually from them. Young birds, at least in captivity, become mature after 5 years, and start breeding after 6 or 7 years.
The main threat for the survival of the Great green macaw was habitat loss. It is estimated that between 1900 and 2000 some 90% of the original habitat has been lost in Costa Rica. Private land not owned by the government is or has been developed into agricultural fields for the production of crops such as oil palm, pineapples, and bananas. As of 2015 Indio-Maíz Biological Reserve in Nicaragua is threatened by settlers moving into the reserve to found farms, especially of subsidence agriculture, oil palm, and cattle. Other threats have included hunting pressure for sport and the feathers and the pet trade. In some areas, Great green macaws are considered pests on maize cultivation and are persecuted for that reason. They have also been killed for food.
According to the IUCN Red List, the total Great green macaw population size is fewer than 2,500 mature individuals or fewer than 3,700 individuals. There were estimated to be 1,530 individuals in southern Nicaragua-northern Costa Rica. Currently, this species is classified as Endangered (EN) on the IUCN Red List, and its numbers today are decreasing.
Due to their diet, Great green macaws may act as seed dispersers; they distribute seeds from the various fruits, particularly of the almond tree Almendro, which these birds are fond of the most.