Plumage balances camouflage and thermoregulation in Horned Larks (Eremophila alpestris)

Abstract

Animal coloration serves many biological functions and must therefore balance potentially competing selective pressures. For example, many animals have camouflage, in which coloration matches the visual background against which predators scan for prey. However, different colors reflect different amounts of solar radiation and may therefore have thermoregulatory implications as well. In this study, we examined geographic variation in dorsal patterning, color, and solar reflectance among Horned Larks (Eremophila alpestris) of the western United States. We found associations between dorsal plumage brightness, hue, and patterning relative to the soil conditions where specimens were collected. Specifically, brighter dorsal plumage corresponded to brighter soil, while redder, more saturated hues in dorsal plumage corresponded to redder soils. Furthermore, backs with more high-contrast patterning were more common among females and also associated with soil that had coarser soil fragments, suggesting that lark plumage has been selected to optimize background matching in different environments. We also found that larks exhibited higher solar reflectance in hotter and more arid environments, which lowers the water requirements for homeothermy. Taken together, these findings suggest that natural selection has balanced camouflage and thermoregulation in Horned Larks across a wide variety of soil types and abiotic conditions.

Neo‐sex chromosome evolution and phenotypic differentiation across an elevational gradient in horned larks (Eremophila alpestris)

“…While most populations of Horned Larks are resident throughout the year (Beason, 2020), there is some evidence of seasonal migration at high latitudes and elevations (Behle, 1942). Dorsal coloration and size in larks are often associated with habitat and soil type (Donald et al, 2017; Mason et al, 2021; Mason & Unitt, 2018), although there is considerable variation among local populations (Niles, 1973; Oberholser, 1902). The extensive phenotypic diversity of Horned Larks across close geographic regions makes this species ideal for studying the role of geographic distance and environment in shaping genetic and morphological variation (Mason et al, 2014).…”

Flexible color segmentation of biological images with the R package recolorize

“…7A), which have striking examples of color pattern repetition within and between species (Remsen Jr, 1984; Vuilleumier, 1969) and colors outside of the human visual spectrum. Birds exhibit nearly all of the features which we have shown tend to foil k-mean clustering (Mason et al, 2021). The most common type of bird specimen preparation (aptly termed a ‘round skin’) is convex, with contours that photograph as color variation similar to Fig.…”

Historical contingency influences the diversity of feather nanostructures in cuckoos

“…Endler, 1992), the focus has chiefly been on exploring the adaptive functions of plumage colors. For example, plumage color has been shown to evolve in response to sexual selection (Cooney et al, 2019, Dale et al, 2015, environmental lighting conditions (Gomez & Théry, 2004, Marcondes & Brumfield, 2019, background color (crypsis, Troscianko et al, 2016, Mason et al, 2023 and climate (thermoregulation, Romano et al, 2019, Rogalla et al, 2021. A large body of research shows that natural and sexual selection are key forces in shaping animal colors (Cuthill et al, 2017, Hill & McGraw, 2006a.…”