CALL them animal code-breakers. Red-breasted nuthatches in the forests of North America have developed ways of distinguishing between the seemingly identical alarm calls of a chickadee. It鈥檚 the first time such subtle eavesdropping has been seen.
The nuthatches tune into alarm calls made by black-capped chickadees when they鈥檙e threatened by owls. To humans, all chickadee alerts sound the same. But nuthatches can tell whether the would-be predators are pygmy owls, which also attack small birds like themselves, or the larger great horned owls, which tend not to.
Christopher Templeton and Erick Greene of the University of Washington at Seattle played nuthatches recordings of chickadee responses to both types of owl. Nuthatches became far more agitated when they heard recordings of the pygmy owls, even 鈥渕obbing鈥� the loudspeaker as if it were a predator (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0605183104).
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Templeton says the nuthatches probably pick up on fine-scale features in the 鈥渃hick-a-dee鈥� call such as the number of harmonic notes, or the length and timing of different syllables. 鈥淥ur study shows just how much goes on in nature that we aren鈥檛 aware of,鈥� says Templeton.
