Territoriality, Social Bonds, and the Evolution of Communal Signaling in Birds

Abstract

Communal signaling-wherein males and females collaborate to produce joint visual or acoustic displays-is perhaps the most complex and least understood form of communication in social animals. Although many communal signals appear to mediate competitive interactions within and between coalitions of individuals, previous studies have highlighted a confusing array of social and environmental factors that may explain the evolution of these displays, and we still lack the global synthesis needed to understand why communal signals are distributed so unevenly across large taxonomic and geographic scales. Here, we use Bayesian phylogenetic models to test whether acoustic communal signals (duets and choruses) are explained by a range of life-history and environmental variables across 10328 bird species worldwide. We estimate that duets and choruses occur in 1830 (18%) species in our sample and are thus considerably more widespread than previously thought. We then show that global patterns in duetting and chorusing, including evolutionary transitions between communal signaling and solo signaling, are not explained by latitude, migration, climate, or habitat, and only weakly correlated with cooperative breeding. Instead, they are most strongly associated with year-round territoriality, typically in conjunction with stable social bonds. Our results suggest that the evolution of communal signals is associated with the coordinated defense of ecological resources by stable coalitions of males and females, and that other widely reported associations are largely by-products of this underlying trend.

Contrasting impacts of land‐use change on phylogenetic and functional diversity of tropical forest birds

“…We complemented the biometric data with foraging stratum and dietary information, comprising a series of binary variables for different diets and feeding strata (compiled from Edwards, Edwards, Hamer, & Davies, ). Finally, we also included an ordinal index of the primary habitat for each species from literature (Tobias et al., ; Table ). For further explanation and rationale, see Appendix .…”

Behavior influences range limits and patterns of coexistence across an elevational gradient in tropical birds

“…Measurements were taken from individual birds mist-netted in the field along the Manu Transect, and from specimens stored in museum collections (Trisos et al 2014, Pigot et al 2016. Third, we quantified territoriality using a recently published global dataset that classified intraspecific territorial defense of all bird species (Tobias et al 2016). The first two principal components explained nearly the entirety of variation, and were related to overall beak size (PC1, 75.96% of variation) and shape (PC2, 21.20% of variation).…”

“…We took the log of each of the four traits and conducted a principal component analysis (PCA) to generate independent axes of variation in beak morphology. See Tobias et al (2016) for further details on the justification and definition of these categories, and data sources. We do not present a distinct analysis on body mass divergence in the main text because our analysis of beak morphology incorporates both differences in size and in shape (body mass divergence is unrelated to elevational overlap, Supplementary material Appendix 1 Fig.…”

“…This is in part because species interactions are thought to be stronger in the tropics (Schemske et al 2009), but also because many tropical species are year-round residents that defend permanent territories in diverse communities containing greater numbers of potential ecological competitors (Tobias et al 2016). In addition, broader scale analyses are needed to test for latitudinal trends in the importance of behavioral interactions in explaining geographical distributions.…”

On the natural history of duetting in White-browed Coucals: sex- and body-size-dependent differences in a collective vocal display

“…Although the significance of avian duetting is still debated, joint territory defence is considered one of the primary functions in many species (Todt and Naguib 2000;Hall 2009;Tobias et al 2016). Other supported hypotheses for the function of duetting include mate guarding (Rogers et al 2006;Seddon and Tobias 2006), recognition and contact between partners (Logue 2007;Mennill and Vehrencamp 2008), ensuring reproductive synchrony (Todt and Hultsch 1982;Hall 2006), and pair commitment (Wickler 1980;Templeton et al 2012).…”