Figure 6.

(a) Periodic variation in the Jay feather structure and colour across a single feather barb. (b) The long period, which is the spacing between neighbouring β-keratin air domains, and the β-keratin domain width. The SAXS scattering was measured as a function of position across the single Jay feather barb, and used one dimensional correlation analysis³¹ of the SAXS data. Electron microscopy (EM) images for the different coloured regions of the jay feather; (c) white region, (d) dark blue region and (e) the black region, where melanin creates the strong absorption of light and no clear β-keratin structure is observed in SAXS nor EM. (f) dynamic scaling of the scattering data for the different regions of the feather barb.