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Date of Graduation
5-7-2020
Semester of Graduation
Spring
Degree Name
Master of Science (MS)
Department
Department of Biology
Second Advisor
Heather P. Griscom
Third Advisor
M. Rockwell Parker
Fourth Advisor
T. Brandt Ryder
Abstract
In urbanized habitats, animals are faced with novel selection pressures such as differences in community structure and increased urban noise. Urban noise pollution can negatively impact songbirds as low-frequency noise often masks portions of birds’ mating signal and reduces signal transmission. Previous research has demonstrated that songs of birds in more urban habitats have structural differences that enhance signal transmission when noise is present. These studies have focused on species that deliver short, stereotyped songs with limited repertoires. Gray catbirds (Dumetella carolinensis, family: Mimidae) sing long bouts containing imitated, improvised, and invented song elements, and therefore may have an increased ability to vary songs in response to noise. I hypothesize that urbanization impacts catbirds’ song structural parameters, such as entropy, duration, and frequency. I recorded male catbird songs at sites along an urban gradient in Virginia and the Washington, D.C. metro region and quantified the degree of urbanization at each site. Song features such as minimum, maximum, and peak frequency increased significantly as noise levels increased, demonstrating that catbirds in more urban areas sing higher frequency songs likely in response to anthropogenic noise. These structural differences limit the negative effects of noise masking for catbirds, even for their long song bouts, and suggest that vocal mimics are responding to anthropogenic noise. Future studies should investigate repertoire size and composition along an urban gradient and if these features correspond with community composition.
