While it is true that many birds are primarily visual animals and may have poor senses of smell, we don’t have very much data on the subject. We do know, however, that new world vultures, kiwis (the flightless birds from New Zealand, not the fruit), and tube-nosed (a.k.a. procellariiform) seabirds lead the pack, having the best avian senses of smell. Not only that, but these birds have some of the most sensitive olfactory systems known in the entire animal kingdom. My lab studies olfaction using procellariiform seabirds as model organisms.
After two decades of research, Gabrielle Nevitt and her collaborators have discovered some amazing things about these “noses with wings”. It had been well known for decades that procellariiform seabirds had an excellent sense of smell from anatomical (Bang 1966) and behavioral studies (Grubb 1972, 1973), but Nevitt was able to show how specific food-related odors attract different species of seabirds, depending on what they prefer to eat. Her results have shown that seabird species feeding on primary consumers (e.g. krill, copepods, etc.) are often attracted to the phytoplankton-derived odorant dimethyl sulfide (DMS; Nevitt et al. 1995), while seabird species foraging higher on the food chain (e.g. predatory fish and squid) tend to be attracted to krill-related odors, such as tri-methyl amine and tri-methyl pyrazine (Nevitt 1999, Nevitt et al. 2004). Furthermore, it was discovered that these birds can detect specific airborne compounds in parts per billion concentrations or lower, which is at least three orders of magnitude (1000x) more sensitive than our noses are for the same odors!
It has now been shown that burrow-nesting Blue Petrels (Halobaena caerulea), Common (Pelecanoides urinatrix) and South-Georgian Diving Petrels (P. georgicus), as well as Thin-billed (Pachyptila belcheri) and Antarctic Prions (P. desolata) use smell to locate their burrows in complete darkness (Bonadonna et al. 2003a, Bonadonna et al. 2003b, Bonadonna et al. 2003c). In another simple, yet elegant, experiment Bonadonna and Nevitt (2004) demonstrated that Antarctic Prions were able to recognize and distinguish their personal odor from the odor of their partner as well as a randomly selected prion. It was found that these birds actually preferred the scent of their partner’s odor to their own, and of the three different odors, they were least interested in the odor of a randomly-selected conspecific.
As always in science, answers only lead to more questions. My lab is currently involved in a multi-year study on Leach’s Storm-Petrels (Oceanodroma leucorhoa) to determine if these diminutive, burrow-nesting seabirds select mates by scent with a particular MHC, a complex cluster of ultra-variable genes involved in immune function. Many more questions related to olfaction in wild animals can and should be addressed; there’s a whole world of discovery out there, who nose what one may find next!