Rather well actually...
Molecular ecologist Silke Steiger, at the Max Planck Institute for Ornithology in Starnberg, Germany, has been conducting a new study, searching for smell-related genes in nine species of birds. Based on his team's research, guess who's been identified as the top sniffer bird?
They looked for genes that encode olfactory receptors, which detect odors. Researchers generally assume that animals with a greater variety of receptors have a better sense of smell. Mice, for example, have close to 1000 working olfactory receptor genes, and humans have roughly 400.Full story at ScienceMag.org.
By this logic, the most acute sense of smell in Steiger's menagerie belongs to the kakapo, a rare nocturnal parrot indigenous to New Zealand. The team estimates that the kakapo has 667 functional olfactory receptor genes.