| Female birds often use male song as an indicator of mate quality; thus the study of song provides scientists insights into reproductive success. White-crowned sparrows are a model organism for studies on song learning and function, but most research has focused on subspecies that are sedentary or short distance dispersers. In these subspecies, ecology appears to influence the cultural evolution of songs. One relatively new selection pressure is anthropogenic noise, created mostly by car traffic. Urban noise resonates at low frequencies and has been shown to influence song frequencies in sedentary populations of song sparrows, great tits, and blackbirds. This study investigates urban noise effects on song structure in a long distance migrant, Zonotrichia leucophrys gambelii, on the wintering grounds. Songs and noise were recorded concurrently across the Fresno-Clovis Metropolitan Area and in outlying rural areas then compared for acoustic differences in frequency and duration. I found that the modulated notes, the buzz and trill, decrease in bandwidth in the presence of noise. The duration of the buzz portion of the song can also be predicted by noise and habitat type. This trend towards short, pure tones in noisy areas is likely an adaptation to be better heard through the roar of the city. |
