Vulture Chick Hatches at Lincoln Park Zoo

A cinereous vulture chick hatched at Lincoln Park Zoo and is now being cared for by Animal Care staff in its initial stages of life.

The chick is the offspring of Leon and Virginia, the vulture pair at Regenstein Birds of Prey. Cinereous vultures are classified as Near Threatened by the International Union for Conservation of Nature, and their populations are declining as a result of food availability and human threats. Thus, this hatch is an important event and the result of a recommendation by the Association of Zoos and Aquariums Cinereous Vulture Species Survival Plan.

Cinereous vultures are monogamous, building nests in trees and rocks. They lay one egg at a time and incubate them for 50–68 days. Once hatched, chicks stay in the nest for four months. Sometimes, eggs are placed in man-made incubators. And, if the parents are inexperienced or unable to adequately provide for their young, the chick may go to a foster parent.

Here’s what may go into a successful bird hatch at Lincoln Park Zoo, once eggs have been laid.

Candling and Radiography

Bird eggs have air pockets, which get larger as chicks get closer to hatching. An internal membrane divides the embryo and the egg cell. As the chick develops in the egg, it pierces the internal membrane with its “egg tooth” and breathes from the air pocket for the first time. This is the “internal pip.” Once this happens, staff can candle the egg and monitor the growth of the embryo inside.

In candling, humans shine a light source upon the egg in a dark space, and that light can illuminate details not otherwise visible. “Once the chick internally pips, we can candle the egg and ideally see the chick’s head, or at least a bill, inside that air cell space,” explains Curator of Birds Nicole Finch-Mason. “Otherwise, the rest of the egg is very dark. And this species has a very thick shell— it’s very hard to see inside even with candling.”

In that case, radiographs can be taken to see if they will show more detail. With this egg, Bird and veterinary staff at the zoo were able to determine through x-ray imaging that the chick was properly positioned.

Monitoring the Egg’s Progress

Staff use the candling process to track the trajectory of the air pocket drawing down over time. They also track the weight of the egg, as eggs lose weight between the time they’re laid and the time they hatch. All the data they get through these methods gives them an idea of how the chick is progressing and lets them know how to adjust the conditions in the incubator to help the egg stay in its ideal parameters.

“We use spreadsheets and formulas in those spreadsheets to help us mathematically calculate weight loss,” Finch-Mason says. “If the chick is deemed ‘too light’ or ‘too heavy’ —the egg weight is higher or lower than that ideal window—that could indicate hatching complications or complications with the embryo.”

During the course of this egg’s development over two to three months, Animal Care staff also worked with SSP experts at other zoos who had reared cinereous vultures to draw upon their experience.

Hatching Hope

The next step is for the chick to pierce through the eggshell, which bird professionals call an “external pip.” The chick will carve a hole or a line along the outside of the shell near its head and work to remove the cap of the egg.

Once that happens, the egg is moved into a machine called a hatcher, which contains a quiet and stable high-humidity environment. There, the chick continues the process of leaving the egg. Hatching can take several days, as the chick must stop and rest often.

This egg made its external pip on Wednesday, May 6, and was out of the shell by the end of the following day.

Next Steps

Now that the young bird is fully hatched and dried a bit, it is being moved into a brooder, a machine with less humidity but still higher temperatures. Slowly, the conditions in the brooder will be adjusted to get it used to regular room temperature conditions.

For up to nine days, the chick will be hand-reared, but with as little human contact as possible to prevent it from imprinting on humans. Care staff will suit up in gowns or Tyvek suits, masks, and gloves and the brooder will be covered by sheets or other materials to prevent the chick from seeing people. Noise will stay at a minimum “so the chick doesn’t associate people or people’s voices with being a parent,” Finch-Mason says. “Our job is to try and keep humans as dissociated as possible to ensure the chick takes on as many species-specific behaviors as possible.”

The young bird will not stay at Lincoln Park Zoo. As Leon and Virginia are not experienced parents and this is their first chick, it will transfer to another AZA zoo for fostering. The cinereous vulture may be moving soon—but will be a native Chicagoan for life!

Check out the video here: