Habitat structure drives the evolution of aerial displays in birds

Abstract

John Endler's sensory drive hypothesis posits that physical properties of the environment may shape signalling traits by determining how effective they are in communicating. Evidence abounds of signalling environment driving selection on colours and vocalizations, yet little is known about its influence on visual signals produced via body movements (i.e., gestural displays). Here, we aimed to perform the most taxonomically comprehensive assessment of sensory drive by testing the hypothesis that habitat structure drives the evolution of aerial sexual displays in passerine birds (order Passeriformes). We base this hypothesis on physical properties of habitats that should allow aerial displays to transmit more broadly in open habitats. To test the hypothesis, we performed Bayesian phylogenetic comparative analyses using species‐level phylogenetic trees and a dataset of 469 species from across the Americas. We found that evolutionary gain of aerial displays is on average six times more frequent in open‐habitat passerines than in forest ones. The influence of habitat structure on the evolution of aerial sexual displays attests to the importance of sensory drive as a deterministic evolutionary force within sexual selection, as opposed to models that assume a purely arbitrary direction of sexual trait evolution.

Partial or complete? The evolution of post‐juvenile moult strategies in passerine birds

“…Because the effect of insolation may apply mainly to species living in open habitats, we further tested for a positive interaction between insolation and habitat openness, but the interaction was negative and not statistically significant ( t = −1.045, p = 0.29). Alternatively, the association between complete post‐juvenile moult and habitat openness may not only be caused by faster feather degradation in open habitats but also because birds inhabiting such environments rely more on their flying abilities to escape predators, display (Menezes & Santos, 2020) or forage, than species living in closed environments (Guallar et al., 2009). A complete post‐juvenile moult would ensure a less worn plumage ready to cope with these challenges during their first year.…”

A global analysis of aerial displays in passerines revealed an effect of habitat, mating system and migratory traits

“…The aerial display data used in this study were obtained through a systematic search of published literature and other resources, using a step-wise approach to improve efficiency. First, unmodified data were obtained from a recent comparative work [13] that has comprehensively mapped this behaviour for New World passerines. Second, species accounts of all passerines not covered by [13] were checked in the Birds of the World (BoW) online database [51], after which, numerous taxonomically or geographically specialized handbooks and papers were examined to obtain descriptions of sexual displays in species for which such information was missing or ambiguous in BoW [52].…”

“…The sensory drive hypothesis posits that the producer's signalling traits and the receiver's sensory system and behaviour have co-evolved under biotic and abiotic environmental conditions, and selection may favour signals maximizing information transmission efficacy in a particular environment [23,24]. A recent comparative study found that aerial displays are more prevalent in open rather than closed (forested) habitats in New World passerines [13]. This may imply that the efficacy of aerial displays in intra-and intersexual communication is higher in open habitats where ambient light levels are higher, making visual signals more conspicuous and enhancing their detectability [25][26][27].…”

Motion: enhancing signals and concealing cues

“…Despite the increasing interest in investigating how the movement of both animals and their background has a concealing function (recently reviewed by Cuthill et al, 2019 ), there has been less focus on how movement affects visual signals. Examples of the importance of these interactions abound – more complex habitats can function to conceal signals: lizards adjust their displays with varying wind conditions to increase signal efficacy ( Bian et al, 2019 ; Ord et al, 2007 ; Ord and Stamps, 2008 ; Ramos and Peters, 2017 ), while habitat structure drives the evolution of aerial sexual displays in birds ( Menezes and Santos, 2020 ). In aquatic habitats, where the light intensity fluctuates and is polarised, visual signals and cues are affected by both the movement of water and the movement of the animal ( Cuthill et al, 2019 ).…”