As corvids, `alala (Hawaiian crows) have a wide range of complex behaviors, particularly when it comes to the art of courtship (see ‘Alala: We’re Getting Closer). Being so intelligent, each individual bird has its own personality, likes, and dislikes. This also applies to their interactions and relationships with birds of the opposite sex.
Now this may sound rather anthropomorphic, but in actual fact we soon learn to recognize the different behavioral patterns of individual birds, which helps to define them as individuals and as breeding pairs.
Each `alala is given a name (See Naming `Alala Chicks), which is a very valuable tool for enabling us to remember these patterns of behavior as well as breeding history, husbandry, and veterinary ailments, even though we record all information formally with studbook number as well. (With 70-plus birds in the captive flock, a name is so much easier to remember than a number.)
When it comes to selecting pairs, genetic management of our shallow gene pool is vitally important to maximize long-term genetic diversity. Being extinct in the wild, there is no hope for bringing new genes into the `alala population. Breeding birds are first selected according to their mean kinship (MK) to the rest of the flock. Put simply, a bird with few relatives in the flock has a low MK, so it is a genetically valuable bird.
A bird’s potential mate is selected according to many factors, most importantly the pair’s inbreeding coefficient (IC). The IC is a measure of how closely related the two individuals in a pair are, based on the chance of their offspring inheriting identical genes from each parent. If the pair is closely related (e.g. mother-son), the IC is high, which is bad news for any offspring that may be produced. To make matters more complex, the interbreeding within the limited `alala gene pool over so many generations now means that birds are actually more closely related than they may initially appear. When selecting pairs, we always try to minimize the IC between the two birds, thereby increasing our chances of producing healthy offspring.
It is not just genetic factors that are important in selecting pairs. In several cases, young pairs that select each other from within a flock of youngsters, not surprisingly, often have the best compatibility…with total lack of regard for the genetic calculations.
Sometimes, a genetically well-matched pairing does not necessarily guarantee good compatibility between the individual birds. So, in some extreme cases, the only contribution that the male makes to the nesting process is a series of copulations during socializations that we call “conjugal visits.” In other cases, the pair may be very compatible, but the male’s exuberance for the breeding season overwhelms the female at the nest. In these cases, we temporarily remove the male so that the female can have time at the nest on her own.
How do we keep track of all of these important genetic and behavioral profiles? Check back soon for Corvid Cupid (part 2).
Lisa Komarczyk is a senior research associate for the San Diego Zoo’s Hawaii Endangered Bird Conservation Program. Read her previous post, Wild Palila Welcomed.