They have sharp eyes - but to what extent do songbirds also use their sense of smell to orient themselves? An experimental study now shows that great tits, which cannot smell, find it relatively difficult to find their way around in their home environment. The results suggest that the importance of the sense of smell in songbirds has been underestimated, the scientists say.
Seeing, hearing, tasting, feeling and smelling - with these "antenna systems" animals gain vital information about their environment. Depending on the species, certain senses are known to be more or less important. Our senses of sight and hearing are particularly important. In dogs and many other animals, on the other hand, the sense of smell plays a prominent role. However, studies have already shown that in humans and animals, several senses often contribute to an overall picture of an impression. In this context, the researchers led by Katharina Mahr from the Konrad Lorenz Institute for Comparative Ethology in Vienna are now turning their attention to the birds.
Do songbirds use smells as a guide?
For a long time it was assumed that smelling played hardly any role for this group of animals. But that has already been clearly refuted: numerous studies have shown that the perception of substances in the air is of considerable importance for many bird species when looking for a partner, recognizing danger and also for orientation. For example, migratory birds and pigeons have been shown to be guided by olfactory information, among other things, when orienting themselves over long distances. However, relatively little research has been done on the role of birds' sense of smell in orientation – Mahr and her colleagues say that this is particularly true for songbirds. Do they only use their sense of sight to orientate themselves in their traditional habitat, or do smells also play a role?
The researchers investigated this question by examining one of the best-known songbirds in our native bird world. The great tit (Parus major) is also at home in urban areas and is a frequent guest at feeding stations in gardens, especially in winter. This species was therefore well suited to investigate whether songbirds use environmental odors to find their way back to feeding sites. For the study, the team captured a total of 112 great tits at feeding sites in their traditional habitats. Only half of the birds then had their sense of smell anaesthetized by treatment with zinc sulphate. This effect lasts for a few days, but leaves no permanent damage. The researchers then released some of the birds at a distance of 400 meters from the capture site - another group was released at a distance of 1.5 kilometers.
Smelling birds find their way back faster
First of all, the evidently crucial importance of the sense of sight became apparent: about the same number of great tits with a disturbed sense of smell as control animals ultimately returned to the feeding stations. "This result was not really surprising since we left the animals out in their familiar environment," says Mahr. However, the birds with an impaired sense of smell returned to the feeding stations noticeably late, as was evident from the evaluations. The fact that the sense of smell obviously affects the ability to orientate is also reflected in a disproportionately increased delay in some of the test animals: "The effect was particularly evident when the birds were released at a greater distance," reports Mahr.
The researchers conclude from these results that the sense of smell is not the decisive, but an important component in the orientation system: "Our results indicate that smells in a familiar environment serve as an important source of information for orientation, despite visual cues," says Mahr . The specific sources of information that the birds use to sniff their way around remain unclear. But there is a lot in the air that could possibly also serve as a guide based on a concentration gradient.
“Similar results were originally obtained in migratory birds. But especially for species such as great tits, which often stay in the breeding areas in winter, orientation and navigation by smell could help to optimize the search for food in times when there is little food available, for example in winter," says senior author Herbert Hoi from Konrad-Lorenz -Institute for comparative behavioral research. According to him, the study underscores the often underestimated importance of the sense of smell in birds: for many bird species, this source of information could also be of greater importance for orientation than previously assumed.
Source: University of Veterinary Medicine, Vienna, specialist article: Frontiers in Ecology and Evolution, doi: 10.3389/fevo.2022.858981