Red-throated Caracara

research

Birds outsmart wasps to feed young

January 06, 2014

A team of SFU biology students has discovered how a species of noisy forest bird, the Red-throated Caracara found in Central and South America, supplies its young with a steady diet of wasp larvae without incurring significant stings from defensive worker wasps.

The team, led by biological sciences student Sean McCann, has spent months at a field station in South America over the past several years to observe the birds’ behaviour. Other team members included students Tanya Jones and Catherine Scott and technician Onour Moeri.

“Researchers had previously thought that the birds must produce powerful wasp-repellant chemicals that allow them to take nests without getting stung, but the hypothesis had never been tested,” says McCann.

In fact, the team discovered that the birds use only physical tactics during their attacks on the social wasps’ nests.

wasp nest

The student researchers observed the birds’ activity at the Nouragues Field Station in French Guiana, where they placed cameras to record the action.

Their surveillance revealed that while smaller wasps abandoned their nests rather than defend them; larger wasps did fly out and attempt to sting the birds, driving them away, sometimes repeatedly.

However, the research team discovered that the birds would then employ rapid ‘fly-by’ tactics to damage or knock down the nests. Eventually, the larger wasps would flee and the birds could resume their meal.

The researchers also experimented with disturbing the wasp nests, and found that mechanical damage alone was sufficient to induce the wasps to abandon their nest.

McCann says that unlike temperate-zone paper wasps that never abandon their young because they only have one chance at reproduction, the adults of swarm-founding Neotropical wasps can cut their losses in the face of catastrophe and start over with a new nest.

“Rather than chemical repellency, the behavioral tactics of the birds appear to rely on the wasps’ ability to swarm and find new nests upon severe nest disturbance,” he says. “They lose the brood in the nest, but retain the worker force.”

Red-throated Caracaras are not only known for their spectacular attacks on fierce wasp nests, but also for their unusually well developed, cooperative breeding system.

The team’s findings, including several videos of bird attacks, were published last month in the journal PLOS ONE.

McCann is currently en route to Honduras with co-researcher and SFU MSc student Catherine Scott where they will continue their research on this bird species.

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