No evidence of song divergence across multiple urban and non-urban populations of Dark-eyed Juncos (Junco hyemalis) in Southern California
Urbanization can affect species by introducing new selection pressures, such as noise pollution and different environmental transmission properties. These selection pressures can potentially trigger divergence between urban and non-urban populations of conspecifics. Songbirds in particular rely on their vocalizations to defend territories and attract mates. Urban songbirds have been shown in some species and some populations to increase the frequencies and reduce the length and trill rate of their songs. This study compares songs from four urban and three non-urban populations of dark-eyed juncos (Junco hyemalis) throughout Southern California. We examined song length, trill rate, minimum frequency, maximum frequency, and bandwidth frequency. All sites showed high variance in these traits. We also analyzed whether there were any differences between songs recorded from one urban junco population in San Diego nearly two decades ago and more recently collected data in 2018-2020. We found no significant differences across sites and between urban and non-urban populations in any of these song features; we also found no significant differences between San Diego junco songs from the 2006/2007 and the 2018-2020 field seasons. These findings partially support and partially are in contrast to previous urban junco song studies. To our knowledge, this is one of only a few studies that found no differences in any song traits examined from multiple urban populations and multiple non-urban populations of the same species.