Breeding Season

Posted at 1:41 pm May 1, 2003 by Alan Lieberman

 Nest BoxBreeding season is, unquestionably, the most exciting time for the biologists in the Hawaii Endangered Bird Conservation Program. This is why we are here, why we come to work in the early morning rain and stay until darkness forces the birds to roost. The first `alala Corvus hawaiiensis egg of the season is greeted with exhilaration and some trepidation. The captive `alala population has, for many seasons, laid eggs that are problematic to say the least. The lack of genetic diversity and the behavioral variability in the breeding adults often produces eggs that are less than perfect.

In order to get the best results from our breeding pairs, we closely monitor the birds using closed-circuit video cameras to determine when pairs are bickering (so we can separate them), when eggs are laid, and when it is best to remove eggs for artificial incubation. Although the females often are good ” sitters,” we elect to remove eggs so that the females will lay additional clutches of eggs for maximum production.

In the first week of May 2003, `alala female Kilakila laid her first egg. Her mate, Pikoi, had been separated the day before after showing signs of aggression. Fortunately, birds have the ability to store sperm for several days, so there was little fear that separating the male from the female would present any problems with fertility. As anticipated, based on past performance, Kilakila proved to be a steady incubator. She continued to lay eggs every other day until her clutch was completed with the fourth egg. Unfortunately, when the clutch was removed, we found one egg broken and one egg with internal membranes that were not intact (e.g. detached air cell). This latter condition is invariably fatal to the egg.

Of the remaining two eggs of the clutch, one egg is fertile and is developing well, and the other egg is too young to determine fertility. The season is off to a good start! A second pair of `alala began laying shortly after Kilikila. The female, Ula, along with her mate Kekoa, began laying in the second week of May with a four-egg clutch. Ula’s breeding history began in 1997, and she usually lays one- or two-egg clutches. We are hoping she will sit well on these four eggs, providing several days of maternal incubation.

Other exciting developments are the hatching and rearing of puaiohi by the adults in their aviaries. After several years of maximum production using artificial hatching and rearing techniques, we are now electing to allow the parents to rear their own chicks in special nest boxes. The goal is to imprint the chicks on the nest boxes, which are designed to be rat resistant. Identical nest boxes will be used in the Alaka`i Swamp where the remnant puaiohi still exist. When these young captive puaiohi are later released, they may very well seek out and use these same nesting opportunities, which will improve the success of the nest with the added protection against rat predation. This may help the chances for the species to recover from its current endangered status.

Alan Lieberman is the program director for the San Diego Zoo’s Hawaii Endangered Bird Conservation Program.

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