Migrating songbirds take survival cues from local birds' 'mob' behaviour

Washington, June 26 : A new Queen's University-led study has shown that migrating songbirds take their survival cues from local winged residents when flying through unfamiliar territory.

Biologists discovered that observing local birds' 'mob' behaviour helps migrants avoid predators.

Biologist Joseph Nocera, who conducted the research while working as an NSERC Postdoctoral Fellow at Queen's under the supervision of Biology professor Laurene Ratcliffe, said that it's a case of 'When in Rome, do as the Romans do.'

Dr. Nocera noted that avoiding predators could substantially increase a bird's chances of survival during migration. But to do that, it first has to recognize who its predators are.

"We believe some prey use social cues from other animals to gain information about potential predators," he said.

For the study, researchers tested whether migratory songbirds observe the anti-predator behaviour of local birds, which are familiar with local predators.

One common form of this self-protecting behaviour is 'mobbing': The birds approach a potential predator, rapidly changing position around its location and performing restless wing and tail movements while emitting loud, broad-frequency calls.

These calls are easily recognizable and act as signals of threat.

Since migrating birds rarely participate in mobs, the researchers speculate that they may gain information about predator location, identity and degree of threat through listening to mob calls of other species residing in the area.

To test this theory, they broadcast playbacks of alarm calls that were familiar (black-capped chickadee, common in North America) and foreign (blue-gray tanager, common in Central America) to birds migrating between Canada and Belize.

The Belizean resident birds responded only to the tanager calls, but migrant birds responded to both the tanagers and the chickadees.

Dr. Ratcliffe said that these results present the first evidence that migrating birds pay attention to the anti-predator behaviour of local birds during migration.

"We suspect that the behaviour will be found to be a low-cost learning opportunity for migrants," Dr. Ratcliffe said.

The study is published on-line in the current issue of the journal Behavioral Ecology and Sociobiology.

ANI