Researchers have long believed that the size of a bird’s crest, the tuft of colorful feathers on top of its head, is a sign of sex appeal. But unlike the peacock‘s elaborate display of fanning out its feathers, for instance, a bird’s crest size costs nothing to make. This makes it an unreliable sign of fitness or fertility.
Making natural cologne, however, is requires a lot of energy.
“The individuals that are secreting the odor are saying, ‘I can do this, despite the fact that I’m giving up some of my metabolic energy,'” Douglas explains.
Crested Auklets Make Their Own Citrus-Scented Cologne
To test his theory that the birds use scent as a sign of fitness in males, Douglas collected dozens of male crested auklets and transported them to Florida. He placed the birds in a specialized chamber filled with purified air that could pick up molecules of the bird’s scent.
After filtering and analyzing the samples, Douglas found octanal, a type of organic compound that is also found in the rind of citrus fruits and perfumes such as Chanel No. 5.
He also discovered that the birds with the largest crests made more octanal than their smaller-crested rivals, suggesting that the tangerine scent is highly attractive to female crested auklets. Douglas found that the smellier birds released more corticosterone, hinting at better levels of fitness.
“Something happened in evolution to favor the production of these chemicals,” Douglas says.
The Discovery Of The Tangerine-Scented Seabirds
Crested auklets were first recorded to emit their own tangerine-scented perfume in 2003 by a team of biologists at Swarthmore College in Pennsylvania.
“It’s like someone is peeling a tangerine next to you,” team lead Julie Hagelin once told Nature journal.
The team found that the perfume is actually a blend of oils in the bird’s feathers. However, the preening gland was found to be odorless, leading researchers to believe that bacteria in its plumage may have something to do with the tangerine scent.
They also discovered that crested auklets prefer the smell of tangerine to animal musk or an odorless control.
Douglas first wrote his paper on crested auklets in 2002. It was published in the journal Behavioral Ecology on May 9.