Bird "Wives" Ruin Males' Songs When Females Approach

March 18, 2009

Some female songbirds sweet singing turns downright catty when another chick enters the picture.

Peruvian warbling antbird couples harmonize to warn rival couples away from their territories. But put a single female nearby and the duet turns into a musical shouting match.

That's the finding of new research on the birds by Joseph Tobias and Nathalie Seddon, a married pair of zoologists from the University of Oxford.

The songs of warbling-antbird pairs usually begin as evenly spaced series of couplets. Females can either meld their tunes to their partner's—or jam the other's signal by jumping in at the wrong time.

The study authors played two sorts of songs for antbird pairs in their Peruvian rain forest homes—duets by rival couples, and the tunes of single intruders.

Threatened by rival pairs, the couple put up a united front, singing rhythmic and coordinated duets. But cooperation broke down when solitary rivals came around.

"Specifically, females responded to unpaired sexual rivals by jamming the signals of their own mates," Tobias and Seddon wrote.

"Perhaps the most striking result is that males don't like females 'jamming' their song," Tobias said. Males "try to avoid [the females'] jamming, suggesting that they perceive it as costly in some way."

The researchers say female antbirds are right to feel threatened: They face "high rates of 'divorce' ... along with evidence of extrapair copulations and occasional polygamy."

Tobias said more research is needed to learn the extent of signal jamming among other animals. The researchers suspect it could play a role in duets and choruses in other birds, social apes, and even the origins of human dance and music.

Tobias and Seddon also want to know whether a female antbird jams her mate's song to make it less sexy "or whether she is simply signaling to the new female that this male is taken."

The research appears in the March 12 online issue of the journal Current Biology.




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