Corvid Cupid (part 2)

Be sure to read Corvid Cupid (part 1).

In order to juggle the socializations of breeding pairs of ‘alala (Hawaiian crows), we closely monitor the nesting activity of every breeding pair through CCTV and analysis of digital video recordings. We mostly monitor two types of behavior:

1) Cup forming: In preparation for the laying of a clutch of eggs, the female (and the male) shape the nesting material into a cup shape by dropping down into center of the nest, pushing out with their wings, and kicking back with their legs. As the laying of the first egg of a clutch becomes more imminent, the female will cup form with increasing frequency, then suddenly stop.

2) Sitting: Several days before the female lays her first egg of the clutch, she begins to show a progressive increase in sitting behavior. “Sitting” can best be described as the female resting her chest and abdomen on the base of the nest cup. This increase in sitting behavior coincides with the drop in cup-forming behavior, indicating to us that the first egg is imminent in the next few days. Once the female has eggs in the nest, this activity results in her brood patch being in contact with the eggs in the process of incubation.

By analyzing cup-forming and sitting behavior, we are able to make many valuable decisions that maximize the production of viable, fertile `alala eggs:

1) In the few incompatible pairs, we are able to predict the best time to temporarily socialize the pair to ensure that the female’s eggs will be fertilized.

2) In the compatible pairs where the male has a tendency to dominate the nest, we can predict when we should limit the time when the male has access to the female and her nest.

3) We always try to have the male separated from the female and the nest whenever there are eggs in the nest; the male’s over-interest can lead to damage of the eggs.

4) Occasionally, we have females who are known to be careless when incubating eggs, so we can watch the precise moment an egg is laid and pull the egg immediately for artificial incubation.

5) Whenever possible, we will always try to let the female incubate her clutch naturally for the first third of the incubation period. But while she is incubating these eggs, we monitor her closely to make sure that the percentage of her time spent sitting in the nest does not drop below 75 to 80 percent. If necessary, we can intervene to prevent eggs going cold.

Consequently, during the `alala breeding season, I spend almost my entire working day sitting in front of our `alala monitors, precisely charting the progress of each of the female’s nesting attempts. At the Hawaii Endangered Bird Conservation Program’s Keauhou Bird Conservation Center on the Big Island, I am ably supported by our recurring seasonal research associate, Jen Holler. Over at the program’s Maui Bird Conservation Center, the entire team chips in with the task of video review and behavioral analysis.

One of the great rewards of this intensive behavioral analysis is that we get to know each of the pairs intimately. Often we will be able to predict and watch the very moment that the female lays an egg. Of course, nothing beats the excitement of pulling a clutch of eggs after more than a week of natural incubation, carefully transporting them to the incubation room in their flask of warm millet, and then candling them to find out that they are fertile, with a healthy young embryo developing inside.

The graph below plots the nesting behavior of female `alala #125, named Loli’i, during the 2009 season, in which she laid three clutches of eggs. The pink line charts the cup forming in preparation for a clutch being laid. The blue line charts the female’s sitting/incubation behavior.

Lisa Komarczyk is a senior research associate for the San Diego Zoo’s Hawaii Endangered Bird Conservation Program.

RELATED POSTS