Tuesday, February 09, 2010

Feathers for Adornment and Touch

Whiskered Auklet / USFWS Photo

A new study of Whiskered Auklets finds that ornamental head feathers help a bird feel its way around in its environment.
The researchers placed individual auklets into a dark experimental maze, designed to resemble a natural crevice, and recorded how often they bumped into things.

Both crested and whiskered auklets bumped their heads 2.5 times more often if their feathers on their heads had been artificially flattened.

Also, "without the aid of the crest, naturally long-crested individuals had more head bumps than short-crested individuals," Dr Seneviratne told the BBC.

The two ornithologists then conducted a wider comparative analysis: checking which bird species sport long ornamental feathers against their lifestyles and where such birds live.

What emerged was a striking pattern.

"Birds that live in complex, cluttered habitats and are active at night tend to have a greater probability to express such facial feathers," says Dr Seneviratne.

"We found a highly significant correlation for the observed trend."
The idea that birds use some feathers for touch is not entirely new, even though the BBC article gives that impression. Many birds have rictal bristles – stiff feathers with few barbs – around their mouths; these have long been thought to have a sensory function. (See examples of bristles on a Spotted Dove, a White-cheeked Barbet, and a Large-tailed Nightjar.) Many songbirds also have filoplumes – long, hairlike feathers. (See examples at the link.) Filoplumes help birds detect the positions of feathers on their wings or backs. So it is not at all surprising that other feathers could be used for touch as well.

What I find interesting is that these types of ornamental feathers are usually discussed in terms of a trade-off. Flamboyant colors or headdresses can make a male bird more attractive to potential partners but require a resource investment that could come at the cost of an individual's survival. In this it seems that a feature could serve both sexual advertisement and survival functions.