Above: researcher Amber Rice studied hybrid chickadees and found that odour may play a role in mate selection among naturally hybridising songbirds. Photo: Lehigh University


THE SENSE OF smell helps chickadees and other songbird species feel the chemistry between themselves and a potential partner, says new research.

The study by Amber Rice, associate professor of evolutionary biology at Lehigh University, Pennsylvania, and PhD student Alex Van Huynh set out to test whether scent could influence the choice of mate.

They looked at black-capped (Poecile atricapillus) and Carolina chickadees (P. carolinensis) which were part of a naturally hybridised population, where the two species come into contact and interbreed, to better understand how existing species are maintained.

They discovered that both species of chickadee, male and female, produced chemically distinct natural oils, and both preferred the smell of their own species, although they do not actively avoid the smell of the other one. And even in the hybrid zone between the two distinct population areas of each species, the ability to smell contributed to maintaining “reproductive isolation”: the tendency not to interbreed.

Ms Rice said: “The sense of smell has been very understudied in birds, particularly songbirds, because they frequently have such impressive plumage and song variation. Some other recent work has documented that species of songbird can smell and prefer their species’ odours, but this is the first example in currently hybridising species that we know of.”

Alex Van Huynh added: “Our results show that not only can odour cues be used by songbirds, potentially as a mate choice cue, but that they can have ecological and evolutionary consequences for songbird species.” One is that hybrid chicks are less likely to hatch, and also have lower cognitive abilities than the pure-species birds.

The researchers analysed the natural oils produced by the birds from their preen glands and tested for preference for a particular smell using a Y-maze (see picture), measuring the amount of time each bird spent with a particular scent.

The experiments indicated a clear preference for same-species whole-body odours in both species of chickadees. The results have been published in Ecology and Evolution.

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