Frequency characteristics of urban house finch songs

Background/Question/Methods

Urbanization has been shown to affect behavior, reproduction and survival of wildlife. Specifically, loud, low frequency urban noise (e.g. car motors) masks communication between avian species. To overcome this, urban House Finches (add scientific name) increase the pitch of their songs; however, it is unclear by what mechanism this shift occurs. To begin characterization of House Finch songs in Salt Lake City, Utah, we recorded songs at three distinct locations from May – July 2012. A fourth site was established in Logan, Utah. Sampling sites were 1 km in radius and separated from each other by at least 3 km.  To measure urban noise, ambient recordings were taken after a bird was recorded. After recording songs, we used Raven Pro to measure minimum and maximum frequencies of each syllable. Each syllable was then classified by visual and auditory inspection. To measure accuracy of classification, two researchers working independently distinguished syllable types. 

Results/Conclusions

Average minimum frequency of syllables for Logan, Sugarhouse, and University of Utah were 2.65 kHz (± 0.062), 2.67 kHz (± 0.054), and 2.62 kHz (± 0.073), respectively. There was no significant difference between site averages (p = 0.838). No correlation between ambient noise (db) and song frequency was found within urban sites (p = 0.823, R² = 0.082).  Sixty-one unique syllable types were found in two recordings, with a total of 488 syllables being typed. There was a 97.5% agreement between the two researchers’ typed syllables. We are currently focusing recording songs from natural populations for comparison to the urban songs.  We are also working on automating syllable selection and typing using frequency modulation.