Male song sparrows that raised more offspring over their lifespans sang less—not more—in response to the songs of younger males, even though their mates were equally likely to pursue extra-pair copulations with either the older males or the younger ones, according to a new study by an international team of researchers. The findings challenge the long-held belief that “older males sing more” to compensate for their reduced ability to compete for mates.

This study is the first to investigate how male songbirds respond vocally to younger males over their full lifespans and in relation to their reproductive success. The researchers analyzed long-term data on more than 1,500 male song sparrows Melospiza melodia from 1989 to 2015 in the San Francisco Bay Area in California, US.

“We found that male song sparrows that were very successful in producing offspring over the course of their lives sang less when they were challenged by a younger singer, not more,” says evolutionary ecologist Niels Dingemanse of the Max Planck Institute for Ornithology in Germany, the first author of the study published in the journal Science Advances. “This is counter to the conventional wisdom in behavioral ecology, which predicts that males should escalate their signals when faced with rivals that could displace them.”