Harpy eagles live high in the rainforest canopy, where they can see for hundreds of metres in every direction. From up there, they spot monkeys, sloths and other animals moving through the trees - and then they swoop down at amazing speed to catch them.
Despite being huge, harpy eagles are surprisingly hard to see. They like to sit very still on a high branch, hidden among the leaves, watching the forest below. Some scientists have spent years in the rainforest hoping for one good look at a wild harpy and never quite managed it.
Harpy parents only raise one chick every two or three years - and they look after that chick for a very long time. The young eagle stays near the nest, learning to hunt, for up to two years before it heads off on its own.
Because the rainforest where they live is shrinking, harpy eagles are now rare. In Panama, scientists carefully track wild harpies and even raise some chicks in special centres so they can be released into the rainforest when they are old enough.