Three layers comprise the canopy, according to Chris C. Park's "Tropical Rainforest." The upper layer consists of dome-shaped crowns of trees that knit together. The dominant trees have sleek trunks with few branches, and are supported by buttress roots, which resemble above-ground veins. A few trees, known as emergents, tower above the canopy and can grow as tall as 75 yards. The middle layer, or subcanopy, is composed of densely situated trees that stand about 10 to 25 yards high. Long-stemmed, woody vines and epiphytes, or plants that grow on other plants for support, often bind subcanopy trees together. Hovering five to 10 feet high, the lower tree layer is composed of young trees that eventually grow into the upper canopy.
Epiphytes abound in the canopy. These plants grow on their hosts but are not parasites. They don't feed on a tree's nutrients. Epiphytes draw sustenance from nutrients in air, rain and detritus on branches. Many of these types of plants, such as lichens, mosses, cacti and ferns, are seen in households. They thrive in a tree's cracks and grooves, where moisture and minerals collect. The canopy is also home to an array of orchids and bromeliads, which are flowering plants with waxy leaves.
The diversity of organisms living in rainforests surpasses other environments. The number of rainforest species range from five to 50 million, according to the Mongabay website. Scientists have just started to inventory species in some rainforests. Capable of digesting cellulose in leaves, primates thrive in the canopy, including sloths, orangutans, lemurs, chimpanzees and many species of monkeys. The screeches of howler monkeys can be heard more than 10 miles away.
Ubiquitous in the canopy, parrots feed on fruits, seeds, leaves and grass. They range in size from the three-inch pygmy parrot to the 39-inch macaw. Birds of prey, such as vultures, eagles and hawks, also inhabit the canopy. Tree-dwelling toucans nest at heights of 65 to 100 feet, and devour fruits. Other fruit-eating birds include tanagers, cotingas and manakins. The chicken-sized hoatzin has claws located on the bends of its wings. When it senses danger, it descends into water and hides. After the danger passes, the hoatzin climbs back up the tree with its claws.