Study shows songbirds react to hostility

MIAMI, Jan. 12 (UPI) -- Songbirds such as swamp sparrows appear to sing sophisticated, hard-to-produce songs in hostile situations, a U.S. university researcher said.

When challenged, male swamp sparrows escalate their vocal performance by increasing the frequency range and speed of their songs, a study by University of Miami biology graduate student Adrienne DuBois said.

The findings add to researchers' understanding of how birds use signals to communicate, DuBois and her colleagues said.

"Vocal performance was thought to be a static characteristic -- set once a song is learned," DuBois said.

"Our results are the first to show that songbirds can modulate vocal performance when it is important to do so," she said.

The study gives researchers "a glimpse" of what birds' brains can do, study co-author and Duke University biology, psychology and neurobiology Professor Steve Nowicki said.

"In a broader sense, we can make assumptions about the way the animal brain develops to support a complex communication system," he said.

Earlier studies have found that what humans hear in a bird's song may only dimly resemble what the bird hears.

Most bird songs are emitted by male rather than female birds, and only mature birds produce a complete song, research has shown.