In the auklet world, 'sexy' is tick-repelling powers

Posted: Sunday, November 11, 2007

ANCHORAGE - The mating ritual was hard to miss.

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It would begin with a soft choking call, progress to vigorous rubbing of bills over plumage, and end with an intertwining of necks.

The citrus-like smell that wafted off the birds was strong.

While the behavior was obvious, its purpose was not, until now. It took biologist Hector Douglas years to uncloak the mystery surrounding the mating rituals of crested auklets, small charcoal-gray seabirds with bright orange bills and feather crests that nest in huge colonies on remote island cliffs in Alaska and Siberia.

Douglas, 48, first became curious about the odor coming off crested auklets in the Aleutian Islands of southwest Alaska in the late 1980s. The birds rub the citrus-like scent on each other during courtship.

Douglas determined that they secrete the scent in wick-like feathers on their backs.

The mating ritual happens quickly with first one bird adopting a horizontal posture, then the other.

"The female will come up and actually rub her bill over the area where these wicklike feathers are, rubbing her bill through the plumage and over the male's plumage," Douglas said. "They become engaged in this reciprocal behavior."

Douglas, an assistant professor of biology at the University of Alaska Fairbanks at the Kuskokwim campus in Bethel, observed the behavior while conducting experiments on St. Lawrence Island in 2005 in the northern Bering Sea.

Douglas concealed chemical dispensers with the citrus-like smell in blocks of construction foam that he painted to resemble rocks. He placed the decoys and models on the fake rocks.

The birds began sniffing around, making low sweeping motions.

"They homed 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," he said.

"They would engage in prolonged loving on the models," Douglas said.

He went back to St. Lawrence Island again this summer. The birds exhibited the same behavior.

Douglas' research was the first time alloanointing, or the transfer of chemicals, has been documented in birds, he said.

He went on to find that the alloanointing has a practical purpose. It helps rid the prospective mate of parasites, particularly ticks.

"The scent contains aldehydes, which repel ticks," Douglas said.

The alloanointing occurs mostly around the neck and head because that is where the birds can't self-preen. The substance is found in a globular mass at the base of the wicklike feathers.

"When crested auklets anoint their mates, they spread these chemical defenses over these hard-to-reach places, helping protect them against ticks," he said.

Douglas determined the citrus-like substance is like Kryptonite to Superman by putting ticks in petri dishes with a synthetic chemical substitute and watching them weaken as they walked across graph paper.

"The ticks exposed to average amounts of citrus scent moved much slower than the controls. They were sluggish, they staggered, and some appeared to be paralyzed," he said.

Douglas suspects that those crested auklets than can emit more of the aldehydes-containing scent are more sexually attractive because they have super tick and mosquito-repelling powers, which they can transfer to their mates.

Douglas put live auklets under a glass reaction kettle and passed an airstream over them to collect and measure volatiles. He found a sevenfold difference between those males that produced the least scent and those that produced the most.

"Humans have pheromones. Mammals have pheromones. It is not clear yet exactly what a pheromone is when it comes to birds," Douglas said. "At this point, I am trying to understand what is the nature of this chemical signal."



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