SNP calls for Zonotrichia leucophrys nuttalli x Z. l. pugetensis hybrid zone

Dataset includes 6419 SNP loci for 169 individuals across the Zonotrichia leucophrys nuttalli x Z. l. pugetensis hybrid zone. Sampling information, including individual ID, locality, lat/long, sex, and whether song data is available is also provided. Songs are archived at the Borror Laboratory of Bioacoustics at Ohio State University

Patterns of Song across Natural and Anthropogenic Soundscapes Suggest That White-Crowned Sparrows Minimize Acoustic Masking and Maximize Signal Content

<div><p>Soundscapes pose both evolutionarily recent and long-standing sources of selection on acoustic communication. We currently know more about the impact of evolutionarily recent human-generated noise on communication than we do about how natural sounds such as pounding surf have shaped communication signals over evolutionary time. Based on signal detection theory, we hypothesized that acoustic phenotypes will vary with both anthropogenic and natural background noise levels and that similar mechanisms of cultural evolution and/or behavioral flexibility may underlie this variation. We studied song characteristics of white-crowned sparrows (<i>Zonotrichia leucophrys nuttalli</i>) across a noise gradient that includes both anthropogenic and natural sources of noise in San Francisco and Marin counties, California, USA. Both anthropogenic and natural soundscapes contain high amplitude low frequency noise (traffic or surf, respectively), so we predicted that birds would produce songs with higher minimum frequencies in areas with higher amplitude background noise to avoid auditory masking. We also anticipated that song minimum frequencies would be higher than the projected lower frequency limit of hearing based on site-specific masking profiles. Background noise was a strong predictor of song minimum frequency, both within a local noise gradient of three urban sites with the same song dialect and cultural evolutionary history, and across the regional noise gradient, which encompasses 11 urban and rural sites, several dialects, and several anthropogenic and natural sources of noise. Among rural sites alone, background noise tended to predict song minimum frequency, indicating that urban sites were not solely responsible for driving the regional pattern. These findings support the hypothesis that songs vary with local and regional soundscapes regardless of the source of noise. Song minimum frequency from five core study sites was also higher than the lower frequency limit of hearing at each site, further supporting the hypothesis that songs vary to transmit through noise in local soundscapes. Minimum frequencies leveled off at noisier sites, suggesting that minimum frequencies are constrained to an upper limit, possibly to retain the information content of wider bandwidths. We found evidence that site noise was a better predictor of song minimum frequency than territory noise in both anthropogenic and natural soundscapes, suggesting that cultural evolution rather than immediate behavioral flexibility is responsible for local song variation. Taken together, these results indicate that soundscapes shape song phenotype across both evolutionarily recent and long-standing soundscapes.</p></div

Map of study sites.

<p>Circles indicate sites within city limits of San Francisco, CA, U.S.A. Triangles indicate sites outside city limits. See text for details on each site.</p

Sound masking profiles and song minimum frequencies for five sites.

<p>The solid black line represents the audibility curve (i.e., hearing threshold in silence; following Dooling 2007) for <i>Z</i>. <i>leucophrys</i>. Colored lines are masking profiles for each site, and are shown only where they occur above the audibility curve. The dashed line represents 12dB above the best (i.e., lowest) intensity of the audiogram of the bird with the best hearing. Where the masking profile crosses the dashed line is the predicted low frequency limit of hearing. The mean song minimum frequency for each site is plotted on the dashed line. Points for two sites are shifted up or down from that line for visual clarity. At each site, the minimum song frequency is higher than the predicted low frequency limit of hearing, and this is most distinctive for two sites: U_{Battery East} and U_{Lake Merced} whose masking profiles cross the dashed line at higher frequencies than the audibility curve. The other three sites have predicted frequency limits much lower than the observed song minimum frequencies (U_{Lobos Dunes}, U_{Inspiration Point}, and R_Commonweal).</p

Rank of models that describe song minimum frequency across all sites.

<p>Rank of models that describe song minimum frequency across all sites.</p

Song minimum frequency is related to background noise levels across all sites.

<p>Song minimum frequency is on the y-axis and the amplitude of background noise is on the x-axis. Urban locations included the San Francisco dialect sampled at U_{Battery East}, U_{Inspiration Point}, and U_{Lobos Dunes} and the U_{Lake Merced} dialect sampled at Lake Merced. See text for dialects at rural locations including R_Commonweal, R_{Abbott's Lagoon}, R_Lighthouse, R_{Schooner Bay}, R_{South Beach}, R_{McClures Beach}, and R_Limantour. The solid line represents model average predictions and the dashed line represents the standard error.</p

Song minimum frequency is related to background noise levels in the same urban dialect.

<p>Song minimum frequency is on the y-axis and the amplitude of background noise is on the x-axis. The San Francisco dialect was sampled at three urban locations, U_{Battery East}, U_{Inspiration Point}, and U_{Lobos Dunes}. The solid line represents model average predictions and the dashed line represents the standard error.</p

Rank of models that describe song minimum frequency across three urban sites, where all birds sing the same dialect.

<p>Rank of models that describe song minimum frequency across three urban sites, where all birds sing the same dialect.</p