Birdsong has interested scientists as well as musicians and composers. Earlier in this blog I wrote about birdsong and two naturalists who had a keen ear for it: Henry David Thoreau and Donald Borror. Most scientists agree that birds sing (and call) to attract a mate, signal danger, indicate where they are, mark their territory and keep rivals out, or keep a flock together. They haven’t much considered whether birds sing for pleasure, but that opens up a large topic--do animals make sounds for fun as well as function--and is for a later blog post. Here I want to write about Kera Belcher and John Quinn’s report on their experiment to see whether Carolina Chickadees altered their songs in response to the sounds of predators. It’s not just the experimental result that interests me, but also what they’d learned from previous studies of birdsong in order to construct their hypothesis.
Belcher, who presented the report, noted that experiments have confirmed that birds change their songs in response to noise interference. That is, they tend to shift frequency to avoid the interference. The Chickadee, they then told us, was among a special class of birds thought to be sentinels, whose danger calls warned other species as well as their own. You may have seen how, in wintertime, chickadees travel in flocks and appear at home feeders with other species such as goldfinch and nuthatch. They do that here in East Penobscot Bay, and they’re also joined by juncos—although the juncos feed on the ground nearby. For their experiment, Belcher and Quinn decided to introduce a predator species to see if it would trigger the alarm call and warn the other birds as well as their own species. Evidently it did, as the Chickadees always arrived first at the feeder after the predator was introduced, before the other species in the flock were seen at the feeder.
In a charming revelation of experimental improvisation, Belcher noted that their simulated predator (a stuffed owl) didn’t stand up to the weather, so they decided that she herself ought to serve as the experimental predator. I can just imagine her swooping down toward the feeder, yelling and waving her arms, in the campus area reserved for the test. Clearly, this is a preliminary experiment; and it wasn't clear to me whether the bird was altering its call in response to noise interference, or simply sounding its normal alarm call in the presence of the predator; but it shows something of the kind of research that’s going on.
|Photo by Jeff Titon, 2004|
In the next entry I’ll write about the ecomusicologies 2014 conference presentation by the Italian scientist, well funded by the Australian government, who’s studying the sounds plants make. Not “how to talk to plants,” as one of the New Age books had it a few decades ago, but ways in which plants produce and respond to sound vibrations, perhaps to communicate with other living beings.