Fig 1.
Variation in average avian visible (300–700 nm) and average near-infrared (700–2100 nm) reflectance and transmission of white body contour feathers.
(a) Representative transmission (top) and reflectance spectra (bottom) for species in this study (top to bottom: Archilochus colubrisi, ruby-throated hummingbird; Accipiter cooperii, Cooper’s hawk; Anas clypeata, northern shoveler; Pelecanus erythrorhynchos, American white pelican; Bubo scandiacus, snowy owl; Pachycephala pectoralis, golden whistler). (b) Dendrograms showing phylogenetic distributions of average avian visible (left) and average near-infrared reflectance. (c) Relationship between average avian visible reflectance and average near-infrared reflectance.
Fig 2.
Morphological variation of white feather barbs.
Scanning electron micrographs of cross-sections through barbs of feathers with the high (a) and low (b) average near-infrared reflectance or high (c) and low (d) relative NIR reflectance after accounting for variation in avian visible reflectance. (a) Megaceryle alcyon, belted kingfisher; (b) Acanthis hornemanni, arctic redpoll; (c) Grallina cyanoleuca, magpie-lark; (d) Bubo scandiacus, snowy owl. Scale: 10 μm. SEM data and images are from Igic et al. [20]. Images were created using a JSM-7401F SEM (JEOL, Tokyo, Japan), at a working distance of 7 mm, and an accelerating voltage of 7 kV.
Table 1.
Pairwise correlations among phylogenetically independent contrasts of feather average reflectance and transmission properties (N = 50).
Table 2.
Eigenvectors and eigenvalues of the first three principal components (PC) from a PCA of 11 feather morphology measurements for 50 bird species.
Table 3.
Effect of feather structure (PC1, PC2, and PC3) on the visible and NIR reflectance and transmission of white feathers, and on body mass.
Estimate (95% CI) refers to the average slope and 95% confidence intervals for analyses run over 100 trees.
Fig 3.
Relationships between feather reflectance and structure.
(a) Average avian visible reflectance in respect to feather size and thickness (PC1). (b) Average avian visible reflectance, (c) average NIR reflectance, and (d) relative NIR reflectance. Values are those predicted from the model and thus show reflectance in respect to the selected PCs while keeping differences in other PCs constant and accounting for phylogeny. Percentages illustrate the proportion of total variance in feather structure explained by principal components.