 by Ned Rozell March 12, 2005
The McKay's bunting is about seven inches tall, is almost pure white, breeds only on two of Alaska's loneliest islands, and stays all winter on the flat-stone beaches of Alaska's western coast, from Kotzebue to the Alaska Peninsula. Researchers at the University of Alaska Museum of the North are trying to figure out more about one of the continent's most seldom-seen songbirds, which could have a population of less than 6,000. The range of McKay's buntings is so limited that the Audubon Society recently put the bird on its "watch list," because a catastrophe on their breeding islands could wipe them out. James Maley is a graduate student at the museum who is trying to learn something about evolution at high latitudes by studying the McKay's bunting, which probably made the genetic split from snow buntings within the last 250,000 years. Male snow buntings have a white front and black back, while male McKay's buntings have only a small patch of black on their wings and tail. McKay's buntings are the whitest songbirds in North America, which is perhaps an adaptation to avoid predators on Alaska's west coast during winter. Most snow buntings escape winter by flying as far south as Texas. McKay's buntings breed only on two remote islands in the Bering Sea-St. Matthew and Hall islands. The rarely seen songbirds leave the islands after breeding and head for Alaska's west coast to feed on seeds and insects on beaches, where they remain long after most snow buntings have headed to warmer places. "They're superbly adapted to winter on the beaches of western Alaska," Maley said. McKay's buntings have remained different than the snow bunting even though the species share the same body size and similar plumage. In summer, snow buntings flood back to the north, breeding on the Pribilofs, Nunivak Island, and St Lawrence Island, but not St. Matthew and Hall islands, the sole breeding grounds of the McKay's buntings. "(McKay's buntings are) just a small entity in a huge ocean of snow buntings," Maley said. Maley is using genetics to explore the question of why the McKay's bunting exists. One possibility is that a group of snow buntings got stuck on St. Matthew and Hall islands during a warming period when glaciers melted and sea levels rose. Isolated for thousands of years, the birds developed whiter feathers than snow buntings. When sea levels dropped again as glaciers locked up water during the last ice age, McKay's buntings resisted breeding with snow buntings even though snow buntings probably returned to the same area. Why? Male McKay's buntings' songs may have changed enough during the isolation period that they didn't attract female snow buntings or McKay's bunting females may have evolved a preference for males that were whiter than snow buntings, Maley said. Another theory is that the ice sheets that covered most of North America cut off a group of snow buntings that would evolve to be McKay's buntings. When the glaciers melted and sea levels rose, the birds retreated to the two islands and didn't breed with snow buntings when they eventually returned to the north. Maley has compared tissue samples of McKay's buntings and snow buntings from the museum's frozen tissue collection. He has also used specimens of birds from as far back as 1882, when a scientist named John Murdoch collected and preserved snow buntings in Barrow. He's got a lot of numbers to crunch before he earns his master's degree, but when Maley finishes he should have a good story about a songbird that's uniquely Alaskan.
This column is provided as
a public service by the Geophysical
Institute, University of Alaska Fairbanks, in cooperation
with the UAF research community. Ned Rozell (nrozell@gi.alaska.edu)
is a science writer at the institute.
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