Begging blue tit nestlings discriminate between the odour of familiar and unfamiliar conspecifics

Marta Rossi, Reinaldo Marfull, Sarah Golüke, Jan Komdeur, Peter Korsten and Barbara A. Caspers

Odours play an important role in the life of many animals, including mammals (also humans), reptiles, amphibians and fish. They use their sense of smell when searching for food, communicating with other individuals, and recognising group or family members. Birds have long been assumed to be an exception to this, as it was common belief that birds have no well-developed sense of smell. Indeed, birds do not show the sniffing behaviour or scent marking of territorial boundaries that many mammals do. Instead, birds typically express elaborate song and bright plumage colours, suggesting that they mostly rely on visual and auditory communication. More recent studies, however, indicate that birds do in fact possess a well-developed sense of smell which they use when searching for food, finding aromatic plants to use as nest material, or even to find their nest when returning to it at night as occurs in some species of seabird. The realisation that birds have a well-developed sense of smell raises the question whether body odours are involved in social communication in birds too, possibly to differentiate between familiar and unfamiliar individuals or to recognise family members.  As social communication based on smell is so widespread in the animal kingdom, we wondered if birds are really an exception to this. To evaluate the idea that body odours may also be used in social communication and differentiating between other individuals in birds, we studied the begging behaviour of nestlings of a common European songbird, the blue tit. Nestlings beg to stimulate their parents to feed them and often compete with nest mates for their parents’ care. Previous studies have reported that nestlings may increase their begging intensity when competing with unfamiliar or less related individuals. Therefore, we specifically investigated whether nestlings vary their begging intensity, depending on whether they are presented with a familiar body odour of themselves and a sibling or an unfamiliar odour of two nestlings from another nest. We found that the nestlings begged longer in response to the unfamiliar body odour, indicating that they can differentiate between familiar and unfamiliar individuals based on smell. This finding provides support to the idea that smell is important in social communication in birds.

Read the article in full here.

 Photo provided by authors.

 

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