One way birds stay clean is by spreading around oil produced by the preen, or uropygial, gland. It’s thought that the oil is primarily used to preserve feathers, but previous studies of bird olfaction have also shown that some species communicate using the oil. Researchers have shown that some birds show a preference for certain oily smells, with some songbirds ditching the father of their chicks if a better smelling stud comes along.

— Read more at Birds Sniff Each Other’s Bacteria to Help Choose a Mate at Smithsonian.

The ursine nose is lined with a vast sheet of specialized tissue, called the epithelium, which is embedded with scent-detecting nerves. Like the human epithelium, these cells have the exceptional ability to regenerate themselves (unlike most other nerves). But a bear's epithelium dwarfs our own. "It is much, much larger than a human's," explained Heiko Jansen, a neuroscientist who researches human and animal physiology at Washington State University. "It's several orders of magnitude larger."

— Read more at What would it be like to smell the world like a bear? at Mashable.