This ghostly image of an owl is actually an imprint the bird's "feather dust" left on the window of a home in the Cumbria, UK town of Kendal. The dust is actually particles of keratin from disintegrating powder down feathers. From the BBC:
Experts from the Royal Society for the Protection of Birds (RSPB) confirmed the bird was most likely a tawny owl because of its size and shape and the fact that they appear in gardens more regularly than others.
Val Osborne, head of the RSPB's wildlife inquiries team, said: "We don't very often see an imprint of a bird that's flown into a window that's this clear and where it's pretty obvious exactly what kind of bird it is.
"This would have been very uncomfortable for the bird but thankfully it looks like it survived as Mr and Mrs Arnold couldn't find it anywhere close by. Sadly, many birds aren't so lucky."