Migrating Birds Understand "Foreign Languages"

Matt Kaplan
for National Geographic News

July 2, 2008

Like avid travelers picking up local languages, migrating birds appear to learn and understand the common calls of unrelated bird species that they encounter during their long journeys, new research reveals.

Birds that remain in one location throughout the year have no difficulty identifying predators, such as hawks, ferrets, and snakes.

Migrators, however, constantly face the threat of encountering predators in their travels that they do not immediately recognize as dangerous.

"When I first came to the jungle in Belize I was overwhelmed by the diversity of snakes," said study author Joe Nocera of Queen's University.

"I realized I couldn't spend my whole day avoiding every snake I saw," he said. "I just had to learn from the locals which ones were dangerous.

"This made me wonder how migrant birds, which were just as naïve as me, dealt with this. I suspected they must be learning from the locals too."

Some ecologists had previously suggested that long-distance travelers pick up cues from local species to obtain information on unfamiliar predators, but evidence for this theory has been thin.

To explore the possibility, researchers at Queen's University in Ontario, Canada, played predator warning calls made by both local and foreign species to birds passing through Belize on long migrations as well as to local birds and monitored their reactions.

The study appears in this month's issue of Behavioral Ecology and Sociobiology.

Local Lingo

Belize is loaded with predators ranging from boa constrictors to ocelots and falcons.

It is also along the main migratory route of 83 bird species that fly south from North America for the winter. While some of these birds finish their migrations in Belize, some continue on toward South America.

Nocera and his colleagues obtained recorded antipredator calls made by large aggressive mobs of blue-grey tanagers and black-capped chickadees and played them to birds in the area.

(Related story: "Chickadees Use Complex Calls for Predator 911" [June 23, 2005])

The scientists expected local birds to respond to the tanager calls, since tanagers are found throughout Belize. But they were not certain if migrants would understand this local avian dialect.

When locals and migrants heard the tanager calls, the team found, they responded with agitation and anxiety by repeatedly making calls themselves and changing their positions.

Remarkably they found that migrants also responded to chickadee antipredator calls, even though chickadees are not found anywhere near Belize. Local birds did not respond to chickadee calls at all.

"That migrants would respond to a species' call that they shouldn't expect to hear within 2,000 kilometers [1,242 miles] of where they were came as a big surprise," Nocera said.

Memories

Lauren Benedict, an avian biologist at the University of California, Berkeley, was not involved with the study.

"It's amazing that even a continent away [the birds] remember and react appropriately to danger signals," she said.

"This illustrates the impressive ability birds have to recognize and remember vocal signals," she continued.

(Related story: "Bird Brains Swap Regions for Baby Babbling, Adult Song" [May 1, 2008])

Laszlo Garamszegi, an ecologist at the University of Antwerp in Belgium, also was not involved with the study.

"These findings are a bit similar to what we found with vocal mimicry," he said.

"We discovered that long-distance migrating birds pick up more new sounds than birds which remain local."