Not all birdsong is created equal, according to a new study on black-capped chickadees by the University of Alberta.

Researchers have learned that the melodies of the birds vary widely by geographical region. Although most humans would be tone deaf to the phenomenon, the songbirds are highly tuned to the subtle differences.

"Most humans wouldn't pick up on them, yet the birds do perceive the variances," said Chris Sturdy, professor of psychology at the U of A and one of the study authors. "These birds can pack a lot of information into a really simple signal."

Sturdy said it's appears that each population of chickadees has its own distinct "accent."

"It's interesting to see actually, this song that everyone for years has thought was invariant, actually does vary in systematic ways that the birds can actually pay attention to."

Researchers worked with birds from Alberta — chickadees are nonmigratory — and used recordings from birds in British Columbia and Ontario to conduct their study.

They focused on the "fee-bee" chickadee call used by the birds to fend off threats or attract a potential mate versus the the ubiquitous "chick-a-dee-dee-dee" song used for communication among flock members.

When exposed to the recordings Alberta-born birds knew their neighbours were singing a different tune.

"You actually train the birds to attend to the song, and they have to either learn to respond by flying to a feeder or withhold responding," Sturdy said.

"In this way we can actually get the birds to tell us what they think of a song."

And it's not just geography at play in acoustic differences. Male and female birds are also modifying the melody, and chickadees are able to distinguish between the two.

"The previous belief was that females didn't even sing," said Sturdy, noting that until now male song has been the dominant area of research.

"People have been studying songbirds forever, but no one to date has documented the fact that female vocal production is symmetrical to males. 

"We taught the birds how to discriminate between the two."

The findings, "Black-capped chickadees categorize songs based on features that vary geographically," were published in the journal Animal Behavior.