Figure 3.
Effects of incident angle and light polarization on specular reflectance of green-winged teal feathers. Male teal shown to illustrate colour changes with incident angle θi in speculum feathers; note that the left wing patch (speculum) is green, while the right one is violet–blue (a). Reflectance spectra for unpolarized light at various incident angles (b). Specular reflectance of s- (c) and p-polarized light (d) at various incident angles (θi) with incident plane perpendicular to barbules; line colours as in (b). Inset in (d) shows reflectance curves at θi = 70° with corresponding images of same feather at each polarization (note inverted shape of curves). (a) Adapted from M. Lamarche.