Chickadee alarm calls: more
than meets the ear
Familiar “chick-a-dee-dee-dee” call
found to carry information on size, threat of predators
Posted June 26, 2005
Courtesy University of Washington
and World Science staff
There’s more than meets the human ear when the black-capped chickadee lets its flock mates know a predator is
near. The little songbirds’ “chick-a-dee-dee-dee” call, familiar to many
throughout North America, is far more subtle and information-packed than we previously imagined, scientists
The birds use that call in many social interactions, including warning of predators.
Writing in the current issue of the research journal Science, researchers reported that chickadees use one of the most sophisticated signaling systems discovered among animals. The calls warn other chickadees not only if a predator is moving rapidly, but also transmit information on the degree of threat posed by stationary predators of different sizes.
Chris Templeton, a doctoral student at the University of Washington and lead author of the study, said chickadees produce two very different alarm signals in response to predators.
When they see flying raptors – birds of prey such as hawks, owls and falcons – they produce a soft, high-pitched “seet” call.
But when they see a motionless or perched predator, the birds use a loud
chick-a-dee-dee-dee alarm to recruit other chickadees, as well as other bird species, to harass or mob the predator.
This call is highly varied and comples, the researchers said.
Analysis of more than 5,000 recorded chickadee mobbing alarm calls made under semi-natural conditions showed that the calls varied with the size of the
predator, the researchers explained. And when the recordings were played back to the birds through speakers, their mobbing behavior was related to the size and threat presented by the potential predator.
Templeton said chickadees can alter their mobbing calls in a number of ways, most of which humans can not hear. Most typically they change the dee dee dee not at the end of the call, sometimes adding five, 10 or 15
“You would certainly might notice a change in the number of dee notes in their call if a neighbor’s cats was around harassing them. With something really dangerous, such as a pygmy-owl perched near some chickadees in our aviary, we heard as many as 23 added
dees,” he said.
Templeton said the research began after he noticed the chickadees responding differently to a variety of predators inside an aviary. So
his group set up an outdoor experiment in a semi-natural aviary with 15 different live perched or leashed predators.
Thirteen of these were birds of prey. Two were mammals, a domestic cat and a ferret, which resembles weasels that prey on small birds.
The birds of prey ranged in size from large owls, such as the great gray owl and great horned owl that usually feed on small mammals, to the small pygmy-owl and the American kestrel that hunt small mammals and birds. The smaller raptors represent a greater threat to the agile chickadees than the larger ones because they are more maneuverable in flight and can readily catch small birds.
“That’s why a pygmy-owl is more dangerous to a chickadee than a great horned owl that has a large hooked beak and big talons. A great horned owl going after a chickadee would be like a
Humvee trying to outmaneuver and catch a Porsche, Templeton said.
The chickadees also were exposed to a perched bobwhite quail, a non-predatory species, as a control animal, and did not react to it.
Templeton said the chickadees are assessing risk on the basis of body size, but since they don’t react to the bobwhite quail, they also seem to be assessing individual species.
In the future, Templeton said he wants to examine the chickadee’s “seet” calls to see if they change in response to different raptors flying above them. If they do, this would be even more impressive, since the birds would have such a brief glimpse as a predator flew by.