The warning call of a chickadee packs more information than previously thought, say scientists who found the songbirds can communicate what type of predator is lurking.

Named for their "chick-a-dee-dee-dee" call, the 13-centimetre-long birds live in deciduous forests throughout North America.

Scientists knew the birds' calls were complex. Now researchers say the calls of the chickadees are some of the most sophisticated in the animal world.

A black-capped chickadee. (Courtesy: Chris Templeton, University of Washington)

Chickadees produce a warning call and another call to show their identity.

Chris Templeton, a doctoral student in biology at the University of Washington, discovered black-capped chickadees add "dees" to the end of the call depending on how threatening a predator is.

Templeton and his colleagues studied how six chickadees in a semi-natural aviary responded to 13 raptors tethered to a perch. The predators ranged from great horned owls that prey on small owls to small pygmy-owls that hunt birds and mammals their own size.

They also tested how chickadees reacted to two mammals, a cat and a weasel. The birds did not react to a non-predatory perched bobwhite quail, which acted as a control in the experiment, the team reported in Friday's issue of the journal Science.

Small raptors like pygmy owls are better able to manoeuvre in flight and therefore pose a greater threat to chickadees than larger predators, despite their larger beaks.

"A great horned owl going after a chickadee would be like a Hummer trying to outmanoeuvre and catch a Porsche," Templeton said in a release.

After analysing more than 5,000 chickadee alarm calls, the team found the birds add about five "dees" for larger birds, and up to 23 when a pygmy owl perched near the chickadees.

To test how the flock responds, the team played back the recorded alarm calls from a hidden speaker. Chickadees reacted by calling more for smaller, more threatening predators.

Templeton's next step is to explore another chickadee call, the "seet," to see if it changes depending on what raptors are flying overhead.