WINDSOR, ON — A University of Windsor biologist is using new sound recording technology to solve the scientific mystery of why breeding pairs of tropical birds sing together in coordinated vocal duets.
The synchronization of male and female songs in tropical birds is so astonishing that human listeners often mistake duets for the songs of a single animal. The function of these coordinated vocal duets has eluded scientists for decades; however a new technology for visualizing the position of these birds is yielding ground-breaking results.
“Many duetting birds live in very thick tropical forests where observing animals is difficult or impossible,” says Daniel Mennill, an associate professor in the Department of Biological Sciences and lead author on a new study published in the journal, Current Biology.
“Until we deployed our multi-microphone recording technology, we lacked a suitable method for understanding where birds are as they perform vocal duets, and what the function of duets might be.”
Dr. Mennill worked with engineers at Cornell University to develop a system of eight microphones that simultaneously record to a laptop computer through 1.2 km of cable.
“Because sound travels relatively slowly through air, we can use the multi-microphone recordings to triangulate the position of duetting birds, even in the thickest tropical forest,” Mennill says.
Research was conducted in the forests of Santa Rosa National Park in northwest Costa Rica, where Mennill recorded the duets of tropical Rufous-and-white Wrens, a species named for its reddish and white feathers. Like most duetting animals, the wrens are highly secretive and perform their duets as they move through the thickest undergrowth in the forest.
“From within the thick foliage in Costa Rica, male and female breeding partners perform beautiful, flute-like duets,” he says. “With this technique, we can find exactly where breeding pairs are while they perform duets, and where males and females move between subsequent duets.”
Results show that male and female wrens approach each other following duets and use them to play a version of the children’s game Marco Polo. “One bird sings, listens for the song of its partner, and moves towards the partner after hearing a response,” Mennill says.
In addition to recording duets in a natural, unprovoked context, Mennill also explored how Rufous-and-white Wrens behave in response to territorial invasions by rival duetting pairs. He used two loudspeakers to simulate the voices of a pair of duetting wrens and found that birds fight duets with more duets.
“As soon as I played the duets of a rival pair, the resident birds’ duet rate shot through the roof, demonstrating that duets play an important role in aggressive territory defense.”
The study, which is funded by the National Geographic Society, the Natural Sciences and Engineering Research Council (NSERC) of Canada, and the Canada Foundation for Innovation, is the first published study to use a multi-microphone technique in a tropical forest.
SOURCE: University of Windsor
University of Windsor biologist unlocking mystery of bird duets
