Electron micrograph of feather barbs (dark horizontal lines) and barbules (diagonal lines) with hooklets (wavy, frayed ends on upper barbules). Public domain photo.
Common Eider male (Somateria mollissima). Public domain photo.
Secretarybird (Sagittarius serpentarius) displaying bristle feathers, which serve as eyelashes. Elegant contour feathers radiate from the back of the head, functioning as a display. Stock photo by Johan Swanepoel.
Club-winged Manakin males (Machaeropterus deliciosus). Left photo by Francesco Veronesi; right photo by Michael Woodruff.
Tawny Frogmouth (Podargus strigoides), displaying its incredibly camouflaged plumage. Photo by Ivan Phillipsen.