Distinct song parts of the endemic marsh grassbird of China vary with latitude and climate among migratory and sedentary populations

Abstract

Birdsong can act as a premating barrier to gene flow through its role in mate attraction and territorial defence. The link between geographic variation in song structure and ecological factors is key to the process of acoustically guided population divergence and isolation. Migratory behaviour is an example of such an ecological factor. In this study, we asked whether latitude and climate can explain song variation among migratory and sedentary populations of the marsh grassbird (Locustella pryeri sinensis), a rare songbird endemic of wetlands of eastern and northeastern China. We investigated two structurally different song parts: a repeating trill part followed by a more variable warble part. We found significant variation in acoustic structure and distinct divergence patterns between the two song parts across a latitudinal gradient and strong acoustic correlations with several bioclimatic variables. The trill part showed an increase in maximum frequency with latitude and the warble part became longer with fewer element types towards three higher latitude, migratory populations. These patterns are in line with a dual function of both song parts, increased sexual selection pressure at higher latitude and a complex impact of climate on song through vegetation and weather conditions.

The relationship between latitude, migration and the evolution of bird song complexity

“…Both ecology and sexual selection are often cited as factors driving geographical patterns of song complexity, but it is rare for researchers to measure their effects in this context. While many studies do attempt to take the environment into account in some way (such as by classifying them as 'boreal' vs. 'tropical' forest or 'open' vs. 'closed' species), only two studies included here actually measured the habitat and acoustic features at their study sites (Irwin 2000, Singh & Price 2015, and another three used mean climate measures (Botero et al 2009, Medina & Francis 2012, Xing et al 2017. Fully to test the ecological hypotheses included in this review the field requires more studies that explicitly quantify the sound space available at varying latitudes and to determine whether more complex songs fill a wider swathe of that space.…”

Rufous‐capped Warblers Basileuterus rufifrons show seasonal, temporal and annual variation in song use

“…, Xing et al . ). Further detailed work on the vocal behaviour of the tropical resident genera Basileuterus , Myioborus and Myiothlypis is necessary to discern large‐scale patterns in repertoire use in the family Parulidae.…”

Song variation in a Neotropical mountain passerine, the Brown-capped Redstart (Myioborus brunniceps), is predicted by geographic isolation and environmental factors

“…2, Table 2) and because variances of some of its spectral features were similar between isolated and non-isolated populations. Most of the climate metrics associated with song variation of the Brown-capped Redstart have been previously identified as factors to model variation of song and of other avian phenotypic features (Sosa-López et al 2013, Xing et al 2017, Sementili-Cardoso and Donatelli 2019, Sheard et al 2020).…”