Non-native birds also brought avian malaria. Once mosquitoes were accidentally introduced, malaria was vectored to native bird species, which have not developed the resistance that non-native birds have. Their one defense was to move to forests in higher elevations where it was too cool for mosquitoes to survive. But even that is no longer a secure redoubt—the warming climate means mosquitoes and diseases are surviving there, too.
An interesting result of Paxton’s honeycreeper research is that it documents the loss of both population and cultural diversity—the different socially learned behaviors unique to different animal groups—says Alison Greggor, a postdoctoral research associate at San Diego Zoo Global’s Institute for Conservation Research, who wasn’t involved in the study. The research “shows that there are fewer distinct families reproducing” because the young “would learn their songs from their parents,” she says.
The loss of cultural diversity can impact a species’ chances of survival, which is particularly important in the face of climate change, says Adolfo Cordero-Rivera, a professor of ecology at the University of Vigo in Spain, who coined the term ethodiversity for animal populations to encompass the diversity of behaviors that are culturally transmitted, originate genetically, or are learned individually. “We don’t know how the environment will change in the future, and which kind of behaviors will be useful when the environment changes.”
At the moment, the survival of the Kauai honeycreepers and other highly endangered birds may depend on captive breeding programs. But cultural behaviors, like songs and foraging skills, haven’t yet been incorporated into many of those programs, Greggor says. “The behavior of animals in conservation breeding facilities before they’re being introduced into the wild is something that is gaining more attention,” she says. “Previously, people would put animals out and then maybe come back six months later and say, ‘Oh, there are this many still alive.’”
But that approach may be changing. A captive breeding program for the akekee and akikiki at San Diego Zoo Global’s Keauhou Bird Conservation Center uses recorded Kauai soundscapes as part of their prerelease training.
In other programs, mature birds are used to train young birds in cultural behaviors before they’re released into the wild, providing parental rearing instead of the usual hand rearing by humans. The benefits are important, Greggor says, because many birds have a critical period when they learn vocalizations and need to hear and see a tutor to learn and make the connection between sound and behavior.
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Some birds need that training very early. Greggor points to evidence that some bird species begin learning even before they’ve hatched. “As soon as their ears start developing, they’re listening for the sounds that are going on around their nest,” she says. “Right after that they can already discriminate between what they’ve been exposed to and what they haven’t been.”