Love songs: Warblers pick up the beat for fertile females in the neighborhood

Riffing on the same song thousands of times a day may not be most men’s idea of how to get the girl, but for the common yellowthroat warbler, it’s music to the lady birds’ ears.

Scientists from the University of California, Davis, recorded nearly 119,000 different variations of the male yellowthroat’s mating song. Call it nature’s ultimate mixtape.

The study, published Oct. 22 in the journal Proceedings of the Royal Society B, showed that males pay attention to what’s happening up to a quarter-mile away and change their singing behaviors to match when neighboring females are fertile.

“We knew that birds were paying attention to what was going on in their own territory, but to be paying attention to a whole neighborhood of complex social interactions and then responding to it is kind of surprising,” said lead author Conor Taff, a postdoctoral fellow in the UC Davis Department of Wildlife, Fisheries and Conservation Biology. He conducted the study as a graduate student in the Department of Evolution and Ecology.

Taff and his colleagues used automatic recording devices strapped to trees at a field site near Saratoga Springs, New York, to record over a thousand hours of songs. Using a spectrogram, they identified 118,472 songs sung by 26 males over two breeding seasons. Taff said one male sang 2,000 songs in one day. (Technically, the common yellowthroat sings one “song” but with thousands of slight variations.)

Previous research has established that many songbirds, including common yellowthroats, are socially monogamous but genetically promiscuous. They have a social mate with whom they raise their young and co-defend their territory. But DNA evidence has shown that more than one male typically sires the eggs in one female’s nest.

This study goes a step further, showing that even while the males have a social mate, they are cuing in on when nearby females are fertile and adjusting the number of songs they sing to attract them. Conversely, when their own mate is fertile, the honeymoon is over — they rarely sing at all. Instead, they closely follow behind her. Taff said this may be to ward off other males that are cuing in to the female’s fertility.

“Elaborate displays and sexual signals are pervasive features of the natural world,” said Taff. “Examining them provides a chance to look at how social interactions evolve.”

The study received funding from the Explorer’s Club, Society for the Study of Evolution, the UC Davis Animal Behavior Graduate Group and the National Science Foundation.

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