Cultural shifts after punctuated environmental stress: a study of song distributions in Dark-eyed Junco and Song Sparrow populations

Abstract

Environmental stress, especially during development, can cause important phenotypic changes in individuals. In songbirds, these stress-induced changes have been shown to include impaired learning of song and reduced song complexity in several species. Typically, developmental stress has been studied in terms of individual variation within a population; however, birdsong, a culturally transmitted trait, may undergo relatively rapid changes if widespread learning impairment results from population-level environmental stress, and these changes could potentially be amplified if affected individuals become the song tutors for future generations. We thus hypothesize that ecosystem-wide stressors may cause population-level changes to birdsong. Here, we use publicly available birdsong recordings to determine whether song differences were evident after an abnormal and severe 2016 drought in western New York State. We analyzed birdsong recordings of two species, the Dark-eyed Junco (Junco hyemalis) and the Song Sparrow (Melospiza melodia), recorded between 2006-2020 in the drought-affected region and, for comparison, in two nearby regions less affected by the drought. The population-level song features of the species with more complex songs (Song Sparrow) changed in the drought area after 2016, but not in the control area. In the species with a more simple song (Dark-eyed Junco), we detected song changes in both regions, suggesting that the drought did not have an outsized effect on song in this species. These findings support a more nuanced hypothesis that stress-induced deficits may disproportionately affect species with songs that are more difficult to learn. These conclusions are tempered by the relatively sparse recording availability from years prior to 2016, but we predict that future longitudinal studies of song evolution in natural populations will be more tractable given the nearly exponential increase in the number of song recordings deposited in public repositories in recent years, making this experimental design a useful framework for future studies.RESUMEN. El estrés ambiental, especialmente durante el desarrollo, puede provocar importantes cambios fenotípicos en los individuos. En las aves cantoras, estos cambios inducidos por el estrés han demostrado incluir el aprendizaje deficiente del canto y la reducción de la complejidad del canto en varias especies. Típicamente, el estrés del desarrollo ha sido estudiado en términos de variación individual dentro de una población; sin embargo, el canto de los pájaros, un rasgo transmitido culturalmente, puede sufrir cambios relativamente rápidos si se produce un deterioro generalizado del aprendizaje como resultado del estrés ambiental a nivel de población, y estos cambios potencialmente se podrían amplificar si los individuos afectados se convierten en los tutores del canto de las generaciones futuras. Así, hipotetizamos que los factores de estrés que afectan a todo el ecosistema pueden provocar cambios en el canto de las aves a nivel poblacional. Aquí, utilizamos gr...

Cooperative breeding in songbirds promotes female song but slows the evolution of song elaboration

“…Exposure to challenging or variable environmental conditions may provide another explanation for the link between cooperative breeding and song stability. Complex songs are hypothesized to be disproportionately affected by stressful environmental conditions during development [44], and such conditions are also theorized to contribute to the development of cooperative breeding [45] or defensive behaviors [46]. The latter theory is bolstered by findings suggesting that cooperative breeding is more common in bird species found in environments with highly variable climates such as Sub-Saharan Africa, Australia, and the tropics [47][48][49].…”