Multiple signaling in a variable environment: expression of song and color traits as a function of ambient sound and light

Abstract

Many animals communicate using more than one signal, and several hypotheses exist to explain the evolution of multiple signals. However, these hypotheses typically assume static selection pressures, and previous work has not addressed how spatial and temporal environmental variation can shape variation in signaling systems. In particular, environmental variability, such as ambient lighting or noise, may affect efficacy (e.g., detectability/perception by receivers) of signals. To examine how signal expression varies intraspecifically as a function of habitat characteristics, we evaluated relationships between spatial environmental variation and song and plumage color expression in a tropical songbird, the Red‐throated Ant‐tanager (Habia fuscicauda) in Panama. We recorded male ant‐tanager song, plucked feathers to measure coloration, and quantified the acoustic and light environments from each male's territory. In addition, we took several morphological measurements from each male to assess the potential information content of song and plumage color. We found that males with redder and more saturated crown plumage occurred on darker territories, and males that sang shorter and lower frequency songs occurred on noisier territories. We also found that more colorful males tended to sing longer and lower frequency songs. Finally, we found that song and color correlated similarly with male morphology (e.g., tarsus length, body mass). Altogether, these results indicate that spatial variation in the environment is related to male coloration and song, and that males might be optimizing color and song expression for their particular territorial environment.

It's not just what you have, but how you use it: solar‐positional and behavioural effects on hummingbird colour appearance during courtship

“…Per sensory drive model (Endler 1992), many environmental factors can influence colour-signal transmission and evolution, including water depth (Seehausen et al 2008) and vertical location in a forest (Endler 1993;Gomez & Thery 2004). Additionally, animals often interact with the environment by seeking out specific lighting conditions (Endler & Thery 1996;Heindl & Winkler 2003;Seehausen et al 2008;Cronin et al 2014;Simpson & McGraw 2018a) or orienting themselves in specific ways relative to the sun (Hamilton 1965;Rutowski et al 2007;Dakin & Montgomerie 2009;Bortolotti et al 2011) to increase their conspicuousness and/or colour contrast. There are also examples of how animals use behaviour, independent of environment, to increase their colour conspicuousness, such as animals covering/hiding colour patches and presenting them only in specific situations (Hansen & Rohwer 1986) or using displays to increase colour detection by catching the attention of the receiver (Ord & Stamps 2008).…”

“…; Cronin et al . ; Simpson & McGraw ) or orienting themselves in specific ways relative to the sun (Hamilton ; Rutowski et al . ; Dakin & Montgomerie ; Bortolotti et al .…”

Experimental trait mismatches uncover specificity of evolutionary links between multiple signaling traits and their interactions in hummingbirds*

“…; Endler et al. ; Simpson and McGraw ). Although these studies have revealed important evolutionary links between environmental/nonsignaling traits and animal signals, questions remain about how and why certain signals coevolve together (or antagonistically).…”

Ecological factors drive the divergence of morphological, colour and behavioural traits in cactus wrens (Aves, Troglodytidae)

“…Thus, the ecological divergence between populations arises due to habitat structure, climate, resource differences and the presence of both predators and competitors [2,4]. In birds, studies that show divergent ecologies acting on colour, morphology and song [5,6] refer to Gloger's, Bergmann's and Allen's rules for morphological traits or the acoustic adaptation hypothesis for vocalizations to explain geographical patterns of phenotypic variation (e.g. [7][8][9][10][11]).…”