How the White-Crowned Sparrow changes its tune to be heard through the urban din

Last October, I was invited by Laurel Serieys (a graduate student at UCLA)  to present a paper at The Wildlife Society’s 20th Annual Conference in a symposium on how urbanization can cause wildlife populations to diverge by altering behavioral, physiological, and genetic aspects of populations occurring in cities compared to non-urban areas. This is an emerging field of research as we are beginning to build a better understanding of how different cities are as habitats for many species, and the different ways by which they may adapt to city life – or not. This approach is part of the research strategy which should help explain some of the broader patterns we are observing in the distribution of biodiversity in the world’s cities.

I spoke about the effects of urban noise on bird song, based on the excellent Masters thesis project by my (now former) graduate student Jenny Phillips, who studied migratory White-Crowned Sparrows spending the winter in California’s Central Valley. Jenny has since gone on to a Ph.D. program at Tulane University, working in the lab of Elizabeth Derryberry, who was on her MS thesis committee (and with whom I intend to continue collaborating to extend this research).

Photo of White-Crowned Sparrow sitting in a fence

A white crowned sparrow framed in the demarcated landscapes of California’s Central Valley. Photo by Madhusudan Katti, 2008.

I just remembered that TWS was recording talks and sessions throughout the conference, and went looking to see if my talk was recorded. Indeed it was! So if you are interested in hearing about some of Jenny’s and my work on urban bird song, have a listen to my talk on this page, which shows you my slides coupled with my ghati-accented voice:

Singing in the urban din: the effects of anthropogenic noise on song structure in urban birds

Note: the audio had glitches when I tried listening through Safari, but worked fine on Google Chrome; YMMV.

Here’s my abstract for that talk:

Female birds often use male song as an indicator of mate quality; thus the study of song provides insights into reproductive success. Song structure is constrained by the acoustic environment with selection favoring songs that transmit best through available channels given ambient noise and atmospheric conditions. Ecology_specifically those components of the environment that influence sound transmission_thus influences the cultural evolution of songs. One relatively new selection pressure on many birds’ song, is anthropogenic noise, from car traffic as well as industrial machinery and other urban sources. Urban noise resonates at low frequencies and has been shown to influence song frequencies in sedentary populations of song sparrows, great tits, and blackbirds. Increase in ambient noise has also been shown to diminish discriminatory ability in female zebra finches. I first present a brief conceptual overview of the potential and documented effects of urban noise on bird song and behavior. I then share results from ongoing studies of the effects of noise on song in White-crowned Sparrow, Zonotrichia leucophrys gambelii, a long distance migrant wintering in urbanizing areas of central California. Songs and noise were recorded across the urban-rural noise gradient in Fresno-Clovis Metropolitan Area and compared for acoustic differences in frequency and duration. Modulated note components of the song, the buzz and trill, decreased in bandwidth with increasing noise. The duration of the buzz portion 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. Playback experiments also found increased latency to respond to territorial simulations under high ambient noise levels. This may contribute to a breakdown of territoriality in urban habitats. Anthropogenic noise is likely to be an important driver of population divergence due to urbanization.

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