For a long time, researchers assumed that the sense of smell did not play a major role in birds. Hearing, sight and taste are the senses most important to our feathered friends, it is believed. But now there are new findings that indicate that the preen gland and the secretion secreted from it make it likely that birds have a sense of smell. In addition, the sense of smell is also used for orientation in some bird species.
The preen gland
Almost all birds have what is known as the preen gland. This is the only skin gland in animals. It is located at the base of its tail on the “rump” and emits an oily secretion every day. With their beaks, the birds distribute the secretion on the feathers, which they care for and make them water-repellent. Above all, waterfowl such as the various duck species lubricate themselves with the rump oil. Due to the unpleasant smell, it also deters enemies. In other species, such as parrots and pigeons, the gland regresses with age. They maintain their plumage with a powder that is formed from the tips of the regrowing feathers.
Researchers have now discovered that the oil from the preen gland also fulfills another function. This is because it changes over the seasons and differs between the sexes in about half of the birds studied. Especially during the mating season, the chemical composition is different than in the other months. It is therefore reasonable to assume that the birds can perceive and interpret the smell of the oil.
What is the purpose of the smell of the rump secretion?
The researchers were able to determine a seasonal variation in the composition of the rump oil in 95% of the bird species examined. They put forward two theses as to what function the smell of the oil could have:
The camouflage of the nest
During the breeding season, the rump secretion contains a particularly large amount of the organic molecule diester. Since the oil in this composition evaporates more slowly and can change the scent of an entire nest, the researchers suspect that the bird parents want to protect their offspring from predators. The oil could be detected above all in ground-breeding birds, whose nests are particularly threatened. If both partners breed here, they have the same share of the molecule. If only one partner breeds, the concentration in its rump secretion is higher.
Communication when looking for a partner
The fact that smell plays a decisive role in the choice of a partner for us humans is nothing new. It could be the same with birds. The researchers suspect that the birds can find out the sex of the other person based on their smell. In addition, the secretion could provide information about whether the bird is suitable for a partnership. Another theory is that young animals can recognize and find their parents by smell.
There are already some studies on the sense of smell of birds. But so far, the assumptions could only be supported by a very thin data base. For example, there are no studies on whether predators can smell the rump secretion at all and to what extent the chemical composition differs between the sexes in different bird species.
Cover photo by Valentin Hintikka on Pixabay
