To Catch A Thief

When biologists study food theft among endangered roseate terns, they find that crime most definitely pays

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But do the birds also pass along their thieving ways? Apparently not. Shealer and Spendelow have yet to see the offspring of a klepto tern resort to stealing. Many questions about kleptoparasitism remain: Why, for example, do terns steal rather than fish for themselves? What are the effects on honest roseates in the population?

Sitting in the blind, watching over the terns, Shealer offers a few speculations. Just as no two humans are alike, he says, neither are two birds. A bird that sees its neighbor fly in with a fish might be tempted to steal it, he says, “but I believe that kleptoparasitism is not just a matter of opportunism.” Nor, he says, is it laziness—a way to avoid the up to an hour-long, 25-mile round-trip flight out to sea to search for sand lances. Perhaps, Shealer speculates, some birds simply discover that they are good at stealing. It does, after all, require exquisite skill, speed and timing. Others might lack the ability and give up after trying once or twice.

Whatever motivates terns to steal, it’s clear that “kleptoparasitism is not a loser’s strategy,” says Shealer.


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