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ambience: chattering cowbirds
Cowbirds lay their eggs in the nests of othe r species, so they’re one of the few birds raised from birth by foster parents. The question is – how do they recognize their own kind when it comes time for them to reproduce? I’m Jim Metzner, and this is the Pulse of the Planet. Mark Hauber, a behavioral ecologist at Cornell University, says that these cowbird orphans recognize other cowbirds as a result of both built-in and learned responses. The first step to this self-identity is likely to be a chatter call that all cowbirds are instinctively drawn to.
“Once young cowbirds leave their host parents, they will seek out these chatter calls in the field. Once they locate a group of birds that produces this chatter call, they will associate with these birds and learn the specifics of what cowbirds look like.”
So, attracted to that chatter call, a cowbird gets introduced to its own kind.
“For instance, males have black feathers with shiny brown heads. Females have brown plumages with robust beaks. These characters may not be incorporated in the genome of the young cowbird, but with the help of the trigger of the chatter call, the young cowbird will eventually associate with its own species and be able to socialize and mate eventually.”
If Dr. Hauber is right, this interweaving of innate and learned behavior is a new insight into how cowbirds have evolved to become a successful species. But it’s also an example of a larger idea that is gaining acceptance in the scientific community.
“What we are finding is that there are no behaviors that are strictly determined genetically. It always appears to be a combination of both environmental and genetic factors.”
To hear about our CD, please visit pulseplanet.com. Pulse of the Planet is made possible by the National Science Foundation. I’m Jim Metzner.
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