afterfeather barbicels barbs barbules bird branched branches bright calamus color coloration colored colorful colors colour coloured colourful colours complex integumentary appendage coverts display distinctive elongated-coverts epidermal-growth extravagant eye-spotted tail eye feather feather’s-eye flying-bird interlocking barbules iridescence iridescent outer-covering pavo peacock peafowl pen phasianidae plumage plume rachis shaft tail vane