This post contributed by Liza Lester, ESA communications officer
On the slopes of the Antisana volcano in Ecuador, the plain-tailed wren sings a sophisticated song. It is not a solo, but a duet, a rapid-fire call-and-response so fast that you might mistake the singers for a single bird, even if you have the luck to stand betwixt them and hear it in Dolby surround.
In the November 4th issue of Science, Eric Fortune and colleagues explain that the singers follow neural notations of the entire song, though they sing only their own part. The authors discovered the mental songs by monitoring neural impulses in the HVC, or “song control nucleus,” in the brains of mated pairs. The birds heard their own duets, recorded before capture, and versions with one partner’s part removed. The authors expected the birds to respond most strongly to their own parts—but this was not the case. Full duets elicited the strongest neural activity.
Comparisons of duets to solos show that both singers adjust their timing to match their partner, but the female leads. They coordinate through complicated mental orchestration. How do wrens use this expensive neurological inheritance? Why did duetting evolve?
Hypotheses pose duetting as an affirmation of the bond between mates, or as an aggressive warning to interlopers who might try to come between them. Others suggest the birds are calling locations to each other, or defending territory. There are a lot of ideas, but not a lot of data.
To attack the data problem, ornithologists Dan Mennill and Sandra Vehrencamp deployed an array of microphones in a Costa Rican forest to triangulate rufous-and-white wrens, singing invisibly in the canopy. The rufous-and-whites used their songs to stay in contact with their mates, and perhaps to cement pair bonds, but also to aggress toward other birds (the rufous-and-whites often divorce, the authors say, so jealous warnings may be called for). The authors believe that the duet is a multipurpose tool, adaptable to different needs and circumstances, and not only by wrens. Other species likely have their own uses for the music.
In further bird synergy last week, two girls, a canoe, and a murmuration of starlings exploded across the internet. [I was certain that James Lipton invented “murmuration” for his 1968 collection of collective birds, An Exaltation of Larks, but it seems that Middle English can claim the credit. It appears in the fifteenth century Book of St Albans (whose authors may have made it up).]
Also in the news:
The threat of emerging illnesses leaping from our domestic animals and primate cousins to take new and virulent form in humans is well known from the graphic stories of ebola, HIV, and swine flu. But sometimes the deadly sharing goes the other way. Jef Akst reports in the Scientist on an outbreak of human metapneumovirus that killed an infant and left another orphaned in a small group of Rwandan mountain gorillas. And Christopher Drew shook up controversy last week, writing in the New York Times about “Why Science Majors Change Their Minds (It’s Just So Darn Hard).” Is science too hard? He also reported on “Where the Women Are: Biology.” Apparently, biology is the softer science (yes, they went there).