A global analysis of bird plumage patterns reveals no association between habitat and camouflage

Abstract

Evidence suggests that animal patterns (motifs) function in camouflage. Irregular mottled patterns can facilitate concealment when stationary in cluttered habitats, whereas regular patterns typically prevent capture during movement in open habitats. Bird plumage patterns have predominantly converged on just four types—mottled (irregular), scales, bars and spots (regular)—and habitat could be driving convergent evolution in avian patterning. Based on sensory ecology, we therefore predict that irregular patterns would be associated with visually noisy closed habitats and that regular patterns would be associated with open habitats. Regular patterns have also been shown to function in communication for sexually competing males to stand-out and attract females, so we predict that male breeding plumage patterns evolved in both open and closed habitats. Here, taking phylogenetic relatedness into account, we investigate ecological selection for bird plumage patterns across the class Aves. We surveyed plumage patterns in 80% of all avian species worldwide. Of these, 2,756 bird species have regular and irregular plumage patterns as well as habitat information. In this subset, we tested whether adult breeding/non-breeding plumages in each sex, and juvenile plumages, were associated with the habitat types found within the species’ geographical distributions. We found no evidence for an association between habitat and plumage patterns across the world’s birds and little phylogenetic signal. We also found that species with regular and irregular plumage patterns were distributed randomly across the world’s eco-regions without being affected by habitat type. These results indicate that at the global spatial and taxonomic scale, habitat does not predict convergent evolution in bird plumage patterns, contrary to the camouflage hypothesis.

Behavioral, morphological, and ecological trait evolution in two clades of New World Sparrows (AimophilaandPeucaea, Passerellidae)

“…Color evolution is often driven by habitat type, with natural selection favoring certain colors, patterns, or lack of patterning (Dunn, Armenta & Whittingham, 2015;Shultz & Burns, 2013;Marcondes & Brumfield, 2019;Miller et al, 2019). However, a global analysis showed that habitat does not predict plumage patterns across birds as a whole (Somveille, Marshall & Gluckman, 2016). We found that unpatterned plumage correlated with open grassland habitat among members of the Aimophila and Peucaea clades, as well as when trait correlation analyses were run using the full tree.…”

Towards an ecology of protective coloration

“…We also do not report non‐significant findings as these are not likely to be a representative sample: although non‐significant results are sometimes provided in studies reporting other significant findings (e.g. Stoner, Caro & Graham, 2003 b ; Kelley, Fitzpatrick & Merilaita, 2013), it is rare that non‐significant findings are reported on their own (but see Somveille, Marshall & Gluckman, 2016) and certainly they are not reported systematically.…”

Where the wild birds go: explaining the differences in migratory destinations across terrestrial bird species

“…To do so, we used the land cover classification in the global MODIS land cover dataset (0.5° resolution, Channan et al 2014). Following a methodology similar to Somveille et al (2016), we coded: forests pixels as closed habitat with a value of 1; savannas, grasslands, wetlands, croplands, snow and ice, and barren or sparsely vegetated pixels as open habitat with a value of 0; and shrublands, woody savannas, and cropland/natural vegetation mosaic pixels as partially closed habitat with a value of 0.5. We then averaged the values of all pixels within each hexagon to obtain a value per hexagon.…”