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Harpy Eagle Chick: A Rough Patch

Harpy eagle chick at 65 days oldThe DNA sex results are in and the San Diego Zoo’s newest harpy eagle is a boy! (Read Beau’s previous blog, Harpy Eagle Chick Doubles Size.)

While male eagles are typically smaller than their female counterparts, as the holidays came and went this youngster was falling behind even the smallest healthy eaglets. The chick began to have trouble breathing, and a trip to the Zoo’s hospital was in order. With expert care from the veterinary staff, the eaglet was able to fight off a respiratory infection.

He wasn’t out of the woods yet, though, and shortly after returning from the hospital, he stopped eating entirely. For almost three weeks, committed care from vets and keepers kept the eagle afloat until he finally regained his appetite.

The chick is now back on track and, at over two months old, weighs in at nearly 6 pounds (2.7 kilograms), or almost 40 times his hatch weight! Each morning, after weighing, the eagle is carried outside in his nest tub and set in an outdoor pen. He is no longer being primarily hand fed but eats from a plate of chopped meat, which keepers set in his nest tub and replace throughout the day. The light gray feathers of his first-year plumage are opening up on his back and wings, and there’s sufficient strength in his legs now to stand for brief periods. Though he still won’t fledge for a few months, he’s beginning to flap his little wings, building up strength for when that day comes, and entertains himself by grabbing (or “footing”) the lining of his nest tub, practicing for even further down the road. Growing as fast as a baby eagle takes lots of energy though, and he still spends most of his day sleeping. At night, the tub with eaglet is brought inside where he is offered one last feeding before lights-out.

This past weekend, the chick hopped out of his nest tub for the first time. It’s just one small step toward fledging and an even smaller step toward independence. In the wild, young harpy eagles may stay around the nest for over a year! Even so, it’s an encouraging show of motivation from a chick that wouldn’t even feed itself three weeks ago.

Beau Parks is a keeper at the San Diego Zoo.

Read the Harpy Eagles blog.

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Harpy Eagle Chick Doubles Size

Harpy eagle chick, day 8Since hatching three weeks ago, the Zoo’s harpy eagle chick has grown from a helpless little ball of fluff to, well, a significantly larger ball of fluff. (Read Beau’s previous blog, Harpy Eagle Chick.) The chick doubled in size in just about a week and now (at almost three weeks) weighs nearly a pound.

At day 15Its little legs, barely wider than a toothpick at hatching, have grown wider than a Bic pen. They’re not even strong enough yet to support the rapidly growing chick, but as the talons grow in and begin to curve downward, the feet are becoming weak, miniature versions of the adult harpy eagle’s lethal killing tools. The adult harpy eagle’s foot can have a span as large as a man’s hand and is capable of exerting over 500 pounds (225 kilograms) per square inch of pressure. That’s more pressure than a gray wolf’s bite and about five times the grip of an average man’s hand!

A puppet in the shape of an adult harpy eagle feeds the chick on day 17. As the baby eagle has grown, its appetite has kept pace! The Avian Propagation Center’s (APC) animal food preparers are now providing skinned mice and rats that are minced into bite-sized pieces before being fed to the hungry chick. Yum! We supplement the chick’s meals with vitamin B and calcium and set them outside each day (weather permitting) to soak up vitamin D from the sunlight. The temperature in the eagle’s brooder is reduced little by little as the chick is able to better regulate its own body temperature. Soon the medium-white fluff ball will be moved out of the brooder’s confines and into a larger nest tub. There, as it gains strength, the eaglet will be able to stand up, stretch its wings and eventually “branch.” (To branch means to leave the nest and begin to climb out onto the surrounding branches.)

The chick's shellNobody knows yet if the eaglet is a boy or a girl. Adult female harpy eagles are significantly larger than their male counterparts, but the only way to definitively sex a baby is with a DNA test. Fortunately, such a test can be performed without laying a finger on the eaglet. As the chick developed inside the egg, blood vessels also formed on the inner surface of the shell. That vascular tissue was left over after hatching and the broken eggshell has been sent off to a lab where technicians will be able to recover enough DNA from the tissue to determine the chick’s sex.

Beau Parks is a keeper at the San Diego Zoo.

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Harpy Eagle Chick

On Monday, December 1, the San Diego Zoo welcomed its newest addition, a baby harpy eagle Harpia harpyja, the 14th hatched at the Zoo since 1994.

The Zoo’s pair of adult harpy eagles laid a single egg in their exhibit on October 10. Ten days later, the egg was pulled and set in an incubator, where its development could be carefully watched by the keepers at the Avian Propagation Center (APC). We weighed the egg daily to make sure that it was losing the right amount of water as the chick developed inside. We also monitored the progression of the embryo using a technique called “candling.”

When a bright light is shone through an egg, it allows the keepers to see what’s happening on the inside and keep an eye on the chick’s development throughout its incubation.

After 51 days in the egg, the chick began its escape the night of November 30, and after a long day of determined pecking, finally broke free at 7:15 the following evening. The new chick, wet and exhausted, weighed in at 2.58 ounces or 73.15 grams (or about half as much as a baseball). It was a humble beginning for one of the world’s largest eagle species. Female harpy eagles (the larger sex) can grow to be 20 pounds (9 kilograms); in the wild, they use their powerful feet and needle-sharp talons to snatch their prey from tree branches in the Central and South American rain forests. All of that seemed a little ambitious at that moment, though, as the freshly-hatched chick curled up to sleep off a long day’s work.

The following morning, we moved the chick into its new home in the APC’s “Brooder Room.” A brooder is a warm, humid box that mimics the environment under a parent bird. It is important that the chick never become imprinted on its human surrogates, so this particular brooder is covered with a towel, set behind a curtain, and continuously serenaded by a CD of soothing rain forest sounds to drown out the keepers’ voices. When it comes time to feed the baby, we put a sheet (or “ghost”) over our head and use a harpy eagle puppet to deliver the food.

The chick finally woke up and took its first small meal of diced pinkie mice at 4 p.m., 21 hours after hatching. It was the beginning of a gluttony that will turn this 73-ounce puffball into the most powerful avian predator on Earth!

Be sure to check back for regular updates.

Beau Parks is a keeper at the San Diego Zoo.

Read another blog about the San Diego Zoo’s harpy eagles