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The Peregrine Fund Notes From The Field
Update on the Harpy Eagle Captive Breeding Program
Saskia Santamaria — in Harpy Eagle Conservation and Research    Share
Harpy Eagles usually lay a clutch of two eggs, and although both may hatch, usually only one chick survives to fledge. Once fledged, the juvenile may stay with its parents for a period of up to two or three years while it learns to hunt and care for itself. Once the young becomes independent and starts looking for its own mate and territory the adults are able to attempt breeding again. This long interval between breeding attempts and resulting slow rate of reproduction makes the species extremely vulnerable to direct human impact, such as persecution (shooting and trapping), long before deforestation destroys their habitat.

The Peregrine Fund started an experimental captive breeding program for Harpy Eagles in the early 1990s to determine if it is possible to captively breed large, long-lived, slow-reproducing tropical forest eagles at a rate high enough to successfully restore the species in the wild where populations have been lost or depleted. Based on first results at the World Center for Birds of Prey, the Neotropical Raptor Center (NRC) was built in Panama to maintain the breeding effort in a naturally tropical climate. Once relocated to Panama, each pair of Harpy Eagles was placed in large enclosures within the forest where they are surrounded by nature, exposed to natural light, humidity, and other weather, and isolated from unnatural noise and disturbance.

The start of the rainy season signals the beginning of the Harpy Eagle breeding season at the NRC, with the first clutches of eggs being laid between April and May. As in nature, clutches are usually of two eggs; the second egg being laid some six days after the first. These eggs are left under the female for a period of natural incubation before being removed about 12-18 days later for artificial incubation. Following this method, we found we can increase the hatching success of fertile eggs over the success achieved by the parents themselves. By removing the eggs we also induce the pair to lay another clutch or two of fertile eggs within the same breeding season, which can last through January the following year. This “recycling” technique can increase annual productivity of a single pair of captive Harpy Eagles to as much as six fertile eggs in a single season, a critical goal for a successful species restoration effort.

When the eggs are removed from the nest they are taken to a laboratory where each one is put inside an incubator with controlled temperature and humidity. On average, each egg takes 52 days to develop and hatch. Once the chick hatches it spends its first month inside a brooder in the laboratory where it grows quickly, increasing in size and weight, and growing enough down feathers to keep warm or cool depending on the weather. Once old enough, the chick is placed in an individual nest-sized chamber facing an adult Harpy Eagle in a large flight enclosure to promote imprinting on its own species. At four months of age the chick has grown enough feathers and is large enough to be placed in a flight enclosure where it can strengthen its wings and fly for the first time. The eaglets remain in these enclosures until time to release them at about 18 months of age.

The success we have accomplished since the relocation of the breeding pairs to the NRC, with a total of 34 chicks hatched, has been wonderful. During this time we have learned valuable lessons about captive breeding techniques which allow us to maximize the number of chicks produced each year by our breeding pairs of eagles. We have learned that it is possible to breed these eagles at a rate fast enough to potentially achieve restoration of the species in the wild.

However, the process of releasing the juvenile birds is lengthy, much like the natural process in the wild of a juvenile learning to hunt and fend for itself over two or three years. For example, chicks hatched at the NRC in 2004 will be released for the first time in 2006, and chicks hatched in 2005 will be released in 2007. These last chicks may not become independent of human care in the wild until 2008, and we would expect them only to begin breeding in the wild in 2010 at the earliest. This lengthy development period has a major effect on the feasibility of restoring this and similar forest eagles, like the Philippine Eagle, to forests from where they have been lost. It can be done, but it is lengthy, taking many people working in the difficult conditions of wet, tropical forest.

Many young birds die from predation (jaguars and other predators) and accidents (snake bites, injury from prey, etc.) before they reach maturity, but normally, those that survive to age of first breeding (four or five years old), continue to live a long life of 30-50 years…provided no one shoots them or captures them! So, a possibility that we will try this year is to release a bonded, breeding pair of eagles to see whether they will quickly establish a territory and begin breeding in the wild. Last month, January 2006, the last chick of the season was returned to the parents to be reared by them in their breeding enclosure. This was done to first prove that this pair is capable of rearing a chick, and to strengthen the bond between the male and the female before they are finally released to the wild as a pair.

As of writing this article, the chick is 45 days old. It has started eating by itself and walking around its nest. But we were anxious on the first day we put it into its parents’ nest. Would they accept the chick and care for it, or would they mistake it for prey? We were much relieved on that first day when it took the female only a short while to get used to her new arrival. After only 30 minutes of looking at the newly arrived, small, downy white chick that continuously “peeped” at her, she settled down to brood the chick and fed it regularly. This kind of innate caring behavior is thought to be triggered by signals like the size and color of the chick, its eyes and other features, as well as the begging calls it makes, and can be relied upon to stimulate the caring behavior from the parents.

It has been very interesting observing them and seeing how the parents have modified their behavior as the chick has grown and developed with almost daily changes in size, weight, and appearance. For example, when the chick was very young, the female wouldn’t leave the nest and would constantly beg for food from her mate who brought it to her at the nest. A month later both adults are actively participating in the feeding of the nestling and even though the chick does not need to be brooded any more, it is still protected from the elements by the adults.

As I write, the adults’ release chamber is being built in the forest of Soberania National Park not far from the banks of the Panama Canal. They will be placed there in the next one or two months, given time to acclimate to their surroundings, and then released. With their strong pair-bond and proven success at breeding and rearing chicks, we hope they will quickly establish a territory, build a nest, and breed again as early as next season. If successful, this pair may become the first captive breeding pair to be released and breed in the wild. Once the adults are released into the wild their chick will be cared for in captivity at the NRC until its turn comes to be released into the wild in 2007, along with five other chicks that were hatched in the NRC in 2005. We will keep you posted on the results of this trial, but in the meantime, if you want to learn what it takes to release captive-reared Harpy Eagles into the wild and our adventures along the way, please read Harpy Eagle Releases Notes from the Field.

Find more articles about Harpy Eagle, Philippine Eagle, Neotropics

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