We usually remove the egg after it is laid so we can artificially incubate it and monitor its development without disturbing the very protective parents. While we are caring for the real egg, we give the parents a fake egg (called a dummy egg) to incubate. This dummy egg serves as a placeholder until the real egg is ready to hatch; without it, the parents would not accept the real egg when we would try to replace it in their nest.
While we were caring for Sisquoc and Shatash’s egg, we weighed it daily to track its weight loss, and we candled it periodically to monitor development inside the shell. During incubation, we noticed that the embryo was slightly in the wrong position to hatch—a malposition. Some malpositions are lethal or need our help to hatch successfully. This embryo’s malposition was not extreme and would not normally need our assistance. What was more concerning was the condition of the membranes surrounding the embryo: loose and saggy when they should have been taut. Concern grew that these membranes would cause difficulty in breathing for the embryo once it moved into the egg’s air cell to begin pulmonary respiration. The loose membranes could adhere to the embryo’s nostrils, suffocating it.
Despite 24-hour care from our keepers and a valiant effort from our veterinary staff, the embryo stopped breathing partway through the hatching process on Sunday, March 16, 2014. The egg was expected to hatch around March 20. The embryo and egg are now at our Pathology Lab; hopefully, we will have more information regarding the cause of death.
Egg mortality is highest at the beginning and at the end of the egg’s incubation period. Sometimes there can be a genetic issue causing the embryo to stop developing. Sometimes the egg can get too hot or too cold during incubation, the egg can get jostled, humidity can be too high or too low, etc. Despite setbacks such as this, our “hatchability” rate at the Safari Park is still very high at over 85% success, much higher than wild eggs that have to contend with nest predators, competitors, and a lack of veterinary support.
So, what’s next for Sisquoc and Shatash? They are still incubating their dummy egg perfectly and are being considered as potential foster parents if another condor egg needs to be parent-reared. They will still sit on the dummy egg, even after the due date of their original egg, but only for about a month or so. After that, they will start to tend to the egg less. We see this behavior in birds that are incubating an infertile egg or an egg that died during incubation. If another condor egg needs to be foster-reared, we can return that egg to their nest, and they will hatch it and raise it as their own. Their drive to care for an egg/chick is so strong that they don’t know or care if it’s not their egg. If another egg doesn’t need fostering, we will remove the dummy egg from their nest. They will then shift from nest-caring duties and spend more time in their flight pen. It may seem sad, but that is what happens to wild birds whose eggs do not hatch.
What’s next for Condor Cam? We have moved the camera to a different nest to show you another of our awesome condor pairs, Sulu and Towich, whose egg is due mid-April. Stay tuned for a blog introducing the new pair.
Thanks so much for all of the comments and condolences regarding the loss of Sisquoc and Shatash’s egg. There are still 30 other California condors at the Safari Park that need us to give them the best care we can. With hope, luck, and your support, we can continue to maximize success for these magnificent birds!
Ron Webb is a senior keeper at the San Diego Zoo Safari Park. Read his previous post,
Egg-citing News on Condor Cam.