Finding a blue feather from a jay’s wing is like finding treasure – I’ve had one in my wallet for a couple of months now. If the feather’s gorgeous blue wasn’t enough, then looking at the structure through a hand lens is extraordinary. Tiny hooklets, on barbules, on barbs, on a quill, rachis or shaft as you prefer. Oh, and this blue feather isn’t really blue but brown. Structural colouration is the trick with light refracted by proteins in the feather.