The striking yodel of a male loon is no veiled threat. Loosely translated, the song means "you come here, and I'll pull all your feathers out," says biologist Charles Walcott of Cornell University in Ithaca, New York. Now, Walcott and colleagues have discovered that loons come up with fresh yodels when they move to new lakes, likely to make them stand out from the crowd.
Earlier studies suggested that loons develop a distinctive yodel at a young age and stick with it. If that were true, Walcott and colleagues reasoned, they might be able to spot individual birds by their yodel. To test the idea, Walcott's team studied two populations of loons--one in Wisconsin and another in Michigan--that had already been banded, so the birds' identities could be confirmed.
Male loons changed their calls only slightly from year to year, the researchers reported online 15 February in Animal Behaviour. But when the males relocated from one lake to another, as 10% to 15% do each year, Walcott's group heard something different. Comparing calls from 13 males recorded before and after a territory switch, researchers found that 12 males changed their songs significantly. "It came as a shock," says Walcott. "At first I didn't believe a word of it."
That begged the question of why the birds were changing their tunes. It turned out that new loons accentuated differences between their calls and that of their predecessors'. This may help ensure that potential rivals know that a new master of the lake has arrived, Walcott says.
Ornithologist Donald Kroodsma of the University of Massachusetts at Amherst says that this study suggests that loons have richer social lives than once thought. "It requires the birds all really know each other," says Kroodsma. "We never give them enough credit for the knowledge they have of their fellow beings."
Related sites
- Listen to a Loon yodel before and after a territory switch
- More on loon yodeling
- Loons in Wisconsin
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