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ORCID
https://orcid.org/0000-0002-5779-8442
Date of Graduation
5-15-2025
Semester of Graduation
Spring
Degree Name
Master of Science (MS)
Department
Department of Biology
First Advisor
Dana Moseley
Second Advisor
Leone Brown
Third Advisor
Heather Griscom
Abstract
Anthropogenic noise is loud and low-frequency (low-pitch) sound with frequencies spanning from 1-2.5 kHz in frequency. In noisy urban areas, many birds sing songs with higher minimum frequencies, which can avoid the masking effects of anthropogenic noise. However, the mechanism for an individual to alter spectral aspects of bird song in real time to avoid the masking effect of urban noise is unknown. Immediate flexibility is the ability a bird may use to shifts their song frequency or amplitude in response to noise fluctuations in the environment. Some species that sing higher frequency songs in noisy habitats are not able to immediately adjust their song frequency. Population differences have been found with bird species that are immediately flexible. The gray catbird (Dumetella carolinensis) is a migratory songbird found in habitats spanning the rural to urban gradient, thus experiencing vastly different noise environments. Recent studies have found that catbirds sing higher minimum, maximum, and peak frequency in noisier habitats. I conducted an observational study and an experiment broadcasting noise across an urban gradient to test if catbirds are immediately flexible in response to urban noise. To do this, I used two different noise stimuli to play to males in the field, a low-frequency noise (1-3.5kHz) that simulated urban noise and a high-frequency noise (6-10kHz) which served as a negative control. A parabolic microphone and a Larson Davis Sound Advisor 831c were used to record singing males prior to noise stimuli playback and during experimental noise playback to detect changes in frequency and amplitude. I found that catbirds sing with immediate flexibility in both frequency and amplitude. Catbirds raised their minimum frequency in response to low-and high frequency noise playbacks. They also lowered their maximum frequency in response to high-frequency noise playbacks. Overall, catbirds sang significantly louder by nearly 2dB in response to low-frequency noise playback compared to their pre-stimuli song. These results indicate that catbirds respond to the problem of urban noise with two potential solutions, (1) singing louder and (2) raising their minimum frequencies which would avoid some of the effects of masking noise. Together these changes to song may lead to benefits in signal transmission and signal detection within urban environments.
