March of the Penguins: A Tough Egg to Crack

This month, the Detroit Zoological Society is bringing you not one, but three blog posts centered around our favorite flippered friends — the penguins who live at the Polk Penguin Conservation Center. (read the first blog post, here) The facility, which had been closed since 2019 due to waterproofing issues, reopened in February, and we can’t wait to share with you all the stories we have been saving over the past two and a half years. 

Next in our March of the Penguins series, learn how animal care staff saved the life of a hatching macaroni penguin.

We’ve all heard stories from friends and family of difficult birthing events, sometimes resulting from a baby that is positioned incorrectly in the birth canal, often called a breech delivery. You may not realize that something similar can happen during the hatching of a bird. 

Fertilized eggs contain all of the nutrients needed to support a chick during development. As the chick grows, an air pocket forms at one end of the egg. For a chick to survive, it must be positioned so that it can push its beak into this air pocket just before it’s time to begin hatching. Some developing chicks are rotated or positioned incorrectly so that they can’t reach this air pocket – this means that the chick can only survive if given assistance. Over the years, bird and veterinary staffs have worked together to assist the hatching of several developing eggs.

Looking inside of a penguin egg.

The bird staff monitors eggs under development very meticulously. They take daily weights to ensure eggs steadily lose weight, a sign that the air pocket, (otherwise known as an air cell) is growing larger.  The staff also shines a special bright light through the eggs, a procedure called candling. Candling allows you to see an outline of the developing chick and air cell. Once incubation nears the end, radiographs can also be taken to visualize the skeleton of the chick and ensure the embryo is positioned normally.

In 2021, the Detroit Zoo had a single fertile macaroni penguin egg. On day 37 of a 37-day incubation period, radiographs were taken to see if the chick was able to hatch normally. The radiographs showed the chick was malpositioned in a way that can be fatal — the chick was rotated, and the beak would not be able to reach the air cell. We could feel the chick moving, and it seemed strong. After discussing our findings, we decided to begin the process of assisting the chick to hatch. 

Dr. Ann Duncan helping the chick hatch.

The shell was cleaned gently, and a Dremel tool was used to make a small opening. A sterile tool was then used to gradually make the opening larger until the position of the chick’s beak could be confirmed.  We then made a very small hole in the membrane overlying the chick’s beak. This allowed the chick to begin breathing air, so that it can stay strong and continue hatching. Chick embryos develop with the yolk sac outside of their abdomen, and as they near hatching, the yolk sac is gradually enveloped inside of the belly to provide nutrients for the first few days. Through the opening in the shell, we could see that the chick needed more time to absorb the yolk sac. We set the chick up in a warm, humid environment, and checked on it frequently. We also began offering one or two drops of water every few hours. 

She has arrived!

The next morning, we were very happy to see that the yolk sac had been mostly absorbed. We removed more of the shell to expose the belly, cleaned the skin over the belly and placed a suture to hold things in place. We then gently coaxed the chick out of the shell. In all, the hatching process took about 24 hours, which mimics the timeline of normal hatching. The macaroni chick is doing well, and is currently learning to swim in the Polk Penguin Conservation Center. She was named Betty and as you can see is full of character. We are very happy to have been given the opportunity to get her started on a long, healthy life.   

Betty in the Polk Penguin Conservation Center.

– Dr. Ann Duncan is the director of animal health for the Detroit Zoological Society.

One thought on “March of the Penguins: A Tough Egg to Crack

  1. That was incredibly interesting to read. It never occurred to me to wonder about the purpose of the air sac inside an egg. So glad the chick survived and is doing well. She’s a cutie!

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