let me rub that suntan lotion on your back for you

A female and male crested auklet, left, engage in alloanointing on St. Lawrence Island in June of 2007. During courtship, females and males intertwine necks, an embrace that helps to distribute the citrus scent in their feathers.
[photo & caption: University of Alaska]

…from the University of Alaska:

Researcher finds amorous avian anointment protects mates

…University of Alaska Fairbanks researcher Hector Douglas has found that, for crested auklets, chemistry has both amorous and practical applications. The birds rub a citrus-like scent, secreted in wick-like feathers on their backs, on each other during courtship, a behavior called alloanointing. It is well known among some mammals, such as peccaries, but until now was not documented among birds. His research also indicates that the behavior could help protect the birds from parasites, such as ticks.

"During courtship the male solicits the female by adopting a horizontal posture and giving a soft choking call," explained Douglas, an assistant professor of biology at UAF’s Kuskokwim Campus. "She rubs her bill and upper body over his wick feathers. Then she offers her wick feathers to the male, and they reciprocate several times, smearing the chemicals over their heads, necks and upper bodies."

Douglas’ findings are published in the German journal Naturwissenschaften, a monthly publication of advances in natural sciences, medicine and technology.

Crested auklets are small black and gray seabirds that nest in huge colonies on remote island cliffs in Alaska and Siberia. They have bright orange bills, white facial plumes and a showy feather crest protruding from their foreheads. Douglas observed the unique mating ritual while conducting experiments with lifelike models of crested auklets on St. Lawrence Island, a remote outpost in the northern Bering Sea just 38 miles from Siberia. Douglas concealed chemical dispensers in blocks of construction foam that he painted to resemble rocks. Then he placed the decoys and models on the blocks.

"The crested auklets searched for the scent with their heads down in a conspicuous sniffing behavior," Douglas said. "They honed in on the scent, rotating their heads to place their nostrils directly over the dispenser. Then they rubbed their bills over the dispensers just as they would on the wick feathers of their partner. Next, the birds rubbed themselves on the lifelike models right in the area where the wick feathers are located." …