Feathered noses: methodological insights into understanding avian olfaction and foraging

Research into avian olfactory abilities has so far attracted relatively limited attention due to their complex nature and methodological difficulties. To address the challenges of avian olfactory research, we screened literature spanning four decades by searching publications in the Web of Science and Google Scholar databases. Based on the analyses of 80 experiments that focused on the foraging behaviour of birds, we highlight significant biases in the study of avian olfactory foraging, emphasizing gaps in bird taxa, geographical regions and methodological approaches. While much attention has been paid to the responses of seabirds to dimethyl sulphide (DMS) or of insectivorous birds to herbivore-induced plant volatiles (HIPVs), olfactory responses of frugivorous or nectarivorous birds remain underexplored. The predominance of studies in temperate regions further limits our understanding of bird olfaction in bird species-rich tropical areas. The detection of general traits of bird olfactory behaviour is difficult especially because of varying methodological approaches and lack of detailed information on bird and odour characteristics. Future research should distinguish between innate and learned olfactory behaviours, address the impact of environmental noise and consider individual and sex-specific differences in response to volatile compounds. Intensifying the consideration of these aspects will improve and deepen our knowledge of bird olfactory foraging behaviour and allow for ecological applications for targeted pest management and fruit dispersal strategies.