According to the Life section of the Guardian this week, crested auklets (Aethia cristatella) use scent to signal attractiveness. Apparently they smell strongly of tangerines. Interesting.
I've never encountered a bird smelling of oranges before, but it's a little known fact that barn owls (specifically the back of barn owls' necks*) smell lovely. I can't really describe the scent, but it's subtle, powdery, musky and quite addictive; tricky when you don't have ready access to a barn owl supply. I was first told this secret by a falconer acquaintance of mine. I must have had an expression on my face which screamed 'I think you've been sniffing something else entirely', so she thrust her barn owl (called Wol) under my nose to prove it. It was really quite an experience.
*Probably all of the barn owl smells nice, but if you want to still have a nose after you've smelt the owl, the back of the neck is the safest spot.