Condor Egg is Fertile!

A California condor egg is examined.

A California condor egg is examined.

We have good news to report: Sisquoc and Shatash’s egg is FERTILE! (See previous post, New Egg for Condors Sisquoc and Shatash.)

California condor Shatash laid the egg on January 27, and we are expecting it to begin the hatching process around March 23. So, it is over one third of the way through its 56-day incubation period. Condor Cam viewers have been watching Sisquoc and Shatash take turns caring for and incubating their egg. Well, actually, they’ve been caring for a wooden egg that we refer to as a “dummy” egg. We use a dummy egg as a type of placeholder until their real egg is ready to hatch.

It’s not as if we don’t trust them with a real egg; on the contrary, they have proven to be very reliable parents! When we place the egg in an incubator and let the parents sit on a dummy egg, we can more closely and conveniently monitor the egg’s progress and offer any necessary assistance without disturbing the doting parents. We weigh the egg every day and candle it every few days. When we candle the egg, we hold it up to a bright light that illuminates the interior of the egg, allowing us to see inside. We can monitor blood vessels, membrane development, embryo growth, and movement. By weighing and candling during the incubation period, we can make sure that the embryo is progressing normally, and if it isn’t, we can prepare to offer help if and when it is needed.

If all goes well during incubation and the egg begins the hatching process, we carefully switch it with the dummy egg while the parents are out in the flight pen eating or sunning. They usually don’t even realize we switched eggs on them; they just return to their incubation duties.

As previously mentioned, both parents take turns sitting on the egg. An incubation bout may only last a few minutes before the parent gets off of the egg and leaves the nest box, or it may sit for the whole day. When the parents take turns on the egg, we call it a nest exchange. Sometimes a nest exchange is immediate: one parent enters the nest, and the other parent gets off of the egg and leaves. Other times, a nest exchange may be long, leaving the egg unattended for up to 30 minutes while the parents are outside eating, bathing, sunning, or socializing. During a long nest exchange, the egg cools down, but not usually enough to endanger the egg, especially with successful and experienced parents like Sisquoc and Shatash. Many times both parents are in the nest area (one may perch in the nearby roost while the other sits on the egg) seemingly keeping each other company.

During nesting season, California condors can be surprisingly territorial and defensive of their nest. Usually, they are very mild-mannered and calm, but when they have a precious egg or chick in the area, they defend it. One of the field biologists in California reported a pair of condors swooping and chasing a black bear away from their nest! Despite being very tough and strong birds, they can be very gentle when it comes to caring for their egg or their chick. Keep checking in on Condor Cam to follow the progress of Sisquoc and Shatash’s egg and eventual chick!

Ron Webb is a senior keeper at the San Diego Zoo Safari Park.

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