To me, one of the most exciting aspects of working with the San Diego Zoo’s Hawaii Endangered Bird Conservation Program (HEBCP) is artificially incubating eggs. `Alala (or Hawaiian crow) eggs are incubated for approximately 22 days until they hatch (see Corvid Cupid). Once we pull an egg from the nest, we are able to monitor the embryo’s developmental progress by regularly candling the egg. Eventually, this enables us to identify the first step of the hatching process: the embryo’s beak pushing into the air cell. The air cell is the pocket of air at the top of the blunt end of the egg. With its beak in the air cell, the embryo’s lungs start to activate, which enables the blood to be drawn in from the vessels wrapped around the inside of the eggshell that had previously been used for gas exchange.
Just before or soon after an embryo first breaks through the eggshell (known as an external pip), we move the egg into a hatcher that is maintained at a constant temperature of 99 degrees Fahrenheit. The hatcher also needs to be very humid so that the hatching chick doesn’t dry out and stick to the membranes and residual albumen found inside the egg. Another important component of the hatching process is for the chick to know that there is a “parent bird” out there waiting for it to hatch. We simulate this by putting speakers inside the hatcher that we use to broadcast `alala vocalizations for a few minutes every hour. Periodically we also tap very gently on the eggs. The embryo often responds to these stimuli by increasing its efforts to hatch out of the egg. While some `alala embryos take up to 36 hours to hatch after the first external pip, we have been spoiled this season with some embryos hatching only 6 hours after they make their external pips. That translates into fewer sleepless nights for HEBCP staff, since externally pipped eggs require frequent monitoring throughout the night, in case we need to intervene and provide assistance.
With these efforts, the `alala flock of the HEBCP has been receiving the welcome addition of new chicks. The 2010 breeding season got off to an encouraging start, with the earliest `alala hatches in the history of the program. As of July 1, 2010, we have so far hatched 12 `alala chicks, with 11 surviving, currently ranging in age from just 1 day to 2 months. This brings the total known population of `alala up to 78 birds.
Each breeding season involves stress, sleepless nights, hard work, and occasionally even a few gray hairs for the staff of HEBCP. But more importantly, we each get the rewarding task of helping to bring `alala chicks into the world and the `alala back from the brink of extinction.
Jeremy Hodges is a research coordinator with the San Diego Zoo’s Hawaii Endangered Bird Conservation Program. Read his previous post, Spring Cleaning in Hawaii.