Noise comes with the territory in urban neighborhoods. To win a mate, birds must sing above the sounds of traffic, lawn mowers, and airplanes. Studies have shown that some birds sing higher-pitched songs in loud areas, presumably to help their voices carry above the low-frequency rumbling of city noise.
Now a study by Cornell Lab of Ornithology graduate student Jenelle Dowling and colleagues has found that some birds take the opposite strategy when coping with another urban challenge: hard surfaces. They sing lower-pitched notes, which transmit better around structures such as houses, garages, and fences.
Dowling conducted the study as part of her research with the Smithsonian Migratory Bird Center. She recorded six bird species in areas with different noise levels at 28 sites in the Smithsonian’s Neighborhood NestWatch citizen-science project.
In areas with a lot of hard surfaces, where high-pitched sounds can reverberate into messy and confusing echoes, the study found that Northern Cardinals and Gray Catbirds sang lower-pitched notes.
However, as noise levels increased, Gray Catbirds, Northern Cardinals, and Carolina Wrens sang higher notes, confirming previous findings that some birds raise their pitch to be heard above background noise.
These results reveal a “catch-22” for urban birds. Higher-pitched songs might be easier to hear in noisy areas, but can echo off of nearby buildings, scrambling the message. The findings are important because a bird’s success depends on song.
“Areas that are both loud and heavily paved may be particularly challenging places for birds to communicate,” Dowling said. “Next we need to look into whether birds are able to adjust songs in ways that translate into higher chances of survival and reproduction in the city.”