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As vocal signals travel through the environment, they gradually attenuate, resulting in a loss of intensity. Furthermore, vocal signals experience habitat-induced degradation, distorting the frequency-time pattern of the signal. Prior studies have demonstrated that the extent to which a signal attenuates or degrades is highly dependent on the structure and frequency characteristics of the signal itself, yet considerably less attention has been payed to whether or not intraspecific variation in the structure of a single song with one known function leads to differences in transmission. Here, we test whether or not different variants of Field Sparrow song, which differ significantly in their frequency characteristics and bandwidth, lead to differences in effective transmission distances by broadcasting a playback at a rural and urban site and calculating signal-to-noise ratios, cross-correlation coefficients, and peak frequency degradation. By selecting re-recording distances that mimic the natural spacing patterns of the species, we are able to draw conclusions about how patterns of degradation and attenuation may influence within- and between territory communication. We found that, despite significant differences in frequency characteristics between song types, all of the song types showed a similar pattern of attenuation across distance. We did, however, find significant differences in the degradation of the song types at distances both within and beyond a typical male’s territory. These results indicate that intraspecific variation in Field Sparrow song structure leads to differences in transmission. These differences in transmission may therefore represent an unexplained source of female choice, and could potentially alter the natural spacing patterns of populations.
Branch, Eric, "Exploring the transmission of different field sparrow (Spizella pusilla) song types" (2018). Honors Theses. 3042.