The harpy is one of the largest species of eagle. As is often the case with birds of prey, females are larger than males. The birds can grow to 36-40 inches. Females weigh between 13 to 20 lbs. Males weigh between 9 and 11 lbs. Its wings are relatively short, enabling the bird to maneuver through its thick-forested surroundings. Harpy eagles mate for life. Large nests made of sticks and branches and lined with softer materials are built at least 90 feet from the ground in huge trees like the kapok tree, the Brazil nut tree, or the Cambara tree. The harpy couple often reuses the same nest over many years. The female lays two eggs, but once the first egg hatches, the remaining egg is ignored and will not hatch. Both parents spend all their time protecting and raising the chick until it fledges, usually within 6 or 7 months, though it returns to the nest over the next 6-10 months for an occasional free meal. A harpy pair will produce a chick every 2-4 years. Young harpy eagles reach sexual maturity between the ages of 4 and 5.