Infrared analysis of contour feathers: The conservation of body heat radiation in birds

1. We examined infrared absorption spectra in contour feathers of 10 species of birds to compare infrared features of the downy and pennaceous regions with the mechanisms of conservation of body heat radiation.2. At 1700 cm−1, a sharp increase in transmittance was observed for downy parts, but not for the distal pennaceous regions.3. The transmittance peak for down may be significant in the conservation of radiation heat: the 1700 cm−1 radiation transmitted by the down is scattered and reflected by the pennaceous region of the contour feather, thereby containing the heat radiation within the feather coat.