Abstract
The importance of olfaction for various avian behaviors has become increasingly evident. So far, the use of olfaction for food detection among raptors has only been demonstrated for Cathartes vultures. The Oriental honey buzzard (Pernis orientalis) is a resident and migrant in Taiwan and regularly forages in apiaries. One of its foods in apiaries is yellow pollen dough, a softball-sized mixture of pollen, soybeans, and sugar that beekeepers provide as a supplementary food for bees. Given that pollen dough is not similar to any naturally occurring food, we hypothesized that buzzards identify the dough’s nutritious contents using olfaction, perhaps in combination with vision. Using a series of choice experiments in which individuals could choose between two doughs, we showed that (1) buzzards almost unerringly chose pollen-containing over pollen lacking doughs when otherwise the doughs were identical in size, shape, and yellow color; (2) buzzards always preferred yellow over black or green doughs if both doughs contained pollen; (3) buzzards still preferred pollen-containing over pollen-lacking doughs when both doughs were black, but at a lower rate than in (1). We statistically excluded the possible influences of the doughs’ relative brightness or of repeat visits by the same individuals. Our experiments thus suggest the use of a ‘multi-modal foraging strategy’ among buzzards whereby olfaction and vision are likely to be both used in identifying food at close distances. We also estimated the olfactory receptor gene repertoire size in the buzzard’s genome which is almost five times as large as that of three other raptor species. Therefore, olfaction is likely of far greater ecological importance to this species than to other raptor species. We suggest that olfaction should be considered in the design of behavioral and genetic studies to better understand the use of multiple senses in avian behaviors.
Highlights
A long-held assumption was that birds rely mostly on vision and hearing because they have been assumed to have a relatively limited sense of smell
The other six individuals did not change their choice during their two visits to same experiment, and we scored them as only one individual-based event
The first result of our experiments was that Oriental honey buzzards clearly selected pollencontaining doughs over pollen-lacking doughs
Summary
A long-held assumption was that birds rely mostly on vision and hearing because they have been assumed to have a relatively limited sense of smell. Birds use olfaction for navigation [8, 9], food detection [10, 11], nest location and material [12, 13] and possibly predator avoidance [14,15,16] and intraspecific communication and recognition [17,18,19,20]. The question arises how birds combine multiple senses to enhance their success in specific behavioral tasks. Olfaction plays an important role in some specific behavioral tasks of birds. We approach this question by testing the use of olfaction by a raptor species and examining the interaction of vision and olfaction in food identification
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