A study published in the January edition of the journal Animal Behaviour documents significant changes in the vocalizations that 'alalā make today, when compared with those recorded in the wild more than a decade ago. The study indicates that although the vocal repertoire continues to be rich and varied, it has changed significantly over time. "This is a significant cultural change in the species," said Patrick Hart, a professor in the Department of Biology at the University of Hawaii at Hilo. "Of particular note is the fact that there appear to be fewer alarm and territory calls in the population, and the frequency of alarm calls is greatly reduced."
The 'alalā, or Hawaiian crow, has been extinct in the wild since 2002, preserved only at the Keauhou and Maui Bird Conservation Centers managed by San Diego Zoo Global's Hawaii Endangered Bird Conservation Program. Scientists hypothesize that the change in vocalizations represents changes in the kind of behaviors necessary to the species while maintained in the protected aviaries of the breeding center.
"The larger number of alarm calls in the wild is likely due to the greater variety of potential threats out there, relative to birds in the aviary," said Ann Tanimoto, bioacoustics lab technician and lead author of the study. "Similarly, the lack of territorial broadcast calls in aviary birds is likely due to their limited interaction with neighboring pairs and their greatly restricted home range."
The study raises some interesting questions for conservationists who are working to recover the species and re-establish them into protected forests of Hawaii. Study authors are quick to point out that it is too soon to know if the calls are lost or are simply not practiced while the birds are in aviaries.
"While we hypothesize that specific alarm calls and territorial vocalizations have been lost as older generations passed away, it may also be possible that these calls were not produced at the center simply due to lack of appropriate stimuli," said Hart. "If individuals are released back into the wild, some of these vocalizations may reappear in their repertoire."
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