The use of odors at different spatial scales: comparing birds with fish

Salmon travel hundreds of kilometers of open ocean and meandering rivers to return to their natal stream to spawn; procellariiform seabirds soar over thousands of kilometers of the ocean's surface searching for foraging opportunities and accurately return to their nesting islands. These large-scale olfactory-guided behaviors are among the most dramatic examples of animal navigation ever described. At much closer ranges, the sense of smell can be used for behaviors as diverse as tracking prey, nest location, and mate selection. Both fish and birds face similar problems interpreting olfactory information in fluid mediums where odors are dispersed as filamentous patches. Similar to insects, which have served as model organisms for investigating olfactory related behaviors, the few fish and bird species that have been studied tend to use olfactory information in conjunction with other sensory modalities. Similar to insects, fish and birds also employ oscillatory or cross-stream movement as sampling mechanisms. This review compares and contrasts the use of odors by fish and birds over a range of spatial scales that span from thousands of kilometers to less than a meter. In so doing, we identify behavioral similarities and new questions that need to be addressed regarding the olfactory ecology of these diverse groups of organisms.