Dirty little secrets: "dress for success" is the key to the mating, game among Arctic ptarmigan.(Naturalists At Large)

Publication: Natural History

Publication Date: 01-JUN-04

Bookmark this article Print this article Link to this article Email this article Digg It! Add to del.icio.us RSS

COPYRIGHT 2004 Natural History Magazine, Inc.

Most birds act as if cleanliness really is next to godliness. Watch any bird for a while, and you will see that it spends a lot of time preening its feathers and bathing in water or dust. Feathers are essential for flight, waterproofing, and insulation, so it is not surprising that maintaining them is a vital part of a bird's daily routine. How to explain, then, the bizarre sartorial metamorphosis we have observed in the male rock ptarmigan, a species of grouse? In just a couple of days in early summer the male ptarmigan suddenly transforms himself from an immaculate, pugnacious white bird that stands tall on large boulders, to a filthy, bedraggled creature that skulks about on the tundra. Why do these birds get so dirty? Equally intriguing, why are their feathers so white and conspicuous to begin with?

Charles Darwin was one early naturalist who took an interest in such plumage changes. Probably referring to the willow ptarmigan, which winters in the boreal forest and flies north in the spring to breed in the Arctic, he argued that the species" superb camouflage--white in winter, brown in summer--supported his idea that natural selection shapes the traits that increase an animal's ability to survive. To buttress his case, he noted that the birds often suffer intense predation in the spring, when the snow melts and the once-camouflaged white plumage stands out dazzlingly against the brown tundra. Our own study of rock ptarmigan in the Canadian High Arctic, assisted by Karen R. Holder, currently a lecturer in biosciences at Loyalist College in Belleville, Ontario, confirms that the bird's strategy as a camouflage artist follows a predictable pattern, at least in females. As it happens, though, the story for males is more complicated than Darwin realized.

For thirteen springs in the 1980s and 1990s, we headed for Sarcpa Lake, on the remote Melville Peninsula at the top end of Hudson Bay. To get there we had to hop and skip from place to place on commercial and chartered airlines. Some years we could take a six hour commercial flight from Montreal that would land more than 1,800 miles to the north, at Hall Beach (population about 625), in what is now the territory of Nunavut. >From there we would charter a Twin Otter to fly us the final...

Read the full article for free courtesy of your local library.