Wednesday, February 20, 2008

Birds Depend On Ants To Be Fed

From Science Daily

In the jungles of Central and South America, a group of birds has evolved a unique way of finding food -- by following hordes of army ants and letting them do all the work. With this type of specialization, these flocks of birds track army-ant swarms through the forest.

When millions of these army ants are on the move, they consume every insect, spider and lizard they come across. Naturally, any animal that hears them coming -- and they're very, very loud -- runs the other way. The army-ant-following birds have learned to take advantage of the swarm by perching above it and preying on insects and other small animals trying to escape.

There's 50 years of research into this ecology and behavior. There are three types of followers with one of them being completely reliant on the army ants for food, presenting a problem almost as unique as the situation itself.

"Over the last 50 years there has been some outstanding work on the ecology and behavior of army-ant-following birds, but the details of how the specialization evolved had not yet been examined," Brumfield said.

There are three main categories of specialization found in army-ant-following birds. The first, called occasional army-ant followers, are the most casual of the three, utilizing the insects to round up food but only as the swarm passes through their territory.

Regular army-ant followers, the next level up in specialization, will follow the army ants outside of the flock's territory but are not completely dependent on the ants to provide food. These birds regularly hunt for themselves.

The final, and perhaps most interesting, category is that of the professional army-ant followers. These birds are completely reliant on the army ants for food, presenting a problem almost as unique as the situation itself.

"These birds depend almost solely on one species of army ant, called Eciton burchellii," said Brumfield. "This makes the professional army-ant followers sensitive to many of the very real threats to this ecosystem, like deforestation, global warming and other similar issues. If anything affects the ant population, it could be devastating for these birds."

The team published their findings recently in "Molecular Phylogenetics and Evolution."

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