Invasive plant erodes local song diversity in a migratory passerine

Abstract

Exotic plant invasions threaten ecosystems globally, but we still know little about the specific consequences for animals. Invasive plants can alter the quality of breeding habitat for songbirds, thereby impacting important demographic traits such as dispersal, philopatry, and age structure. These demographic effects may in turn alter song-learning conditions to affect song structure and diversity. We studied Chipping Sparrows (Spizella passerina) breeding in six savannas that were either dominated by native vegetation or invaded by spotted knapweed (Centaurea stoebe), an exotic forb known to diminish food resources and reproductive success. Here, we report that the prevalence of older birds was relatively low in knapweed-invaded habitat, where recruitment of yearlings compensated for diminished site fidelity to sustain territory abundance. In both habitat types, yearling males tended to adopt songs similar to their neighbors and match the songs of older birds rather than introducing new song types, a pattern seen in many songbird species. As a consequence, in invaded habitat where age structure was skewed away from older birds serving as potential song models, yearlings converged on fewer song types. Similarity of songs among individuals was significantly higher and the overall number of song types averaged nearly 20% lower in invaded relative to native habitat. Degradation of habitat quality generally impacts site fidelity and age ratios in migratory songbirds and hence may commonly alter song-learning conditions. Associated shifts in song attributes known to influence reproductive success could in turn enforce demographic declines driven by habitat degradation. Local song structure may serve as an important indicator of habitat quality and population status for songbirds.

Response of bluebunch wheatgrass to invasion: Differences in competitive ability among invader‐experienced and invader‐naïve populations

“…Ongoing invasion of habitats by non‐native species is changing the environment and consequently altering plant community dynamics (Ortega, Benson, & Greene, ; Pearson, ). Although there is limited data on trait changes in response to invasion, an increasing number of investigations are addressing this topic—not only because it is ecologically interesting, but also because of its relevance for making informed management decisions.…”

Loss of vocal culture and fitness costs in a critically endangered songbird

“…If vocal development is compromised by infrequent interactions with appropriate tutors, it could affect the maintenance of population-level vocal culture [7,8]. Evidence that vocal cultures can erode in small or sparse populations is well documented in humans [9], but limited in other species, despite many animal populations increasingly occurring at lower density [10][11][12][13][14]. Whether the loss of vocal culture can incur fitness costs and exacerbate population decline remains poorly understood.…”

Effects of wildfire on vegetation and understory avian communities in montane rainforests, north‐eastern Tanzania

“…Jeffrey and Çağan (2015) explained that invasive trees may compete with native tree species and alter food resources and nesting sites. Invasive plant species are also associated with lower species richness and high nest predation rate (Borgmann & Rodewald, 2004; Ortega et al., 2014).…”