When photographer Mike Yip saw a flash of white on Vancouver Island in British Columbia in late May, the bright movement looked familiar. It wasn't the first time he had seen white ravens.
This time, the rare birds were two youngsters who were still with their parents. When he saw them again two weeks later, the birds were on their own.
Yip, a retired teacher who is a bird photojournalist, spotted the ravens in Coombs, a small community west of Qualicum Beach.
Yip said he first heard of white ravens in the '90s before he was even interested in birding, but didn't see his first ones until 2007. Since then, he has photographed nine different white ravens.
But he rarely sees adult birds.
"With one or two white ravens born almost every year for 20 years, one would expect a lot of white ravens in the area. However, that is not the case," he tells MNN. "All the white ravens that I've seen have been first-year birds. I have never seen or heard of an adult white raven. My theory is that none of the ravens survive the the winter. They probably die of hypothermia because their feathers lack the thermal quality and strength of regular feathers."
Yip says his theory is supported by the observations of a friend whose neighbor fed ravens for several years. By late November, only the black siblings would show up, while the white siblings mysteriously disappeared. In addition, he says, two times over different years, there were reports of white raven bodies being found.
Albinism in animals
This year's birds have light blue eyes, which suggests they could have a genetic defect that prevents them from forming certain melanin pigments, Ben Freeman, a researcher at the University of British Columbia's Biodiversity Research Center, told the Vancouver Sun.
Albino animals have no melanin anywhere in their bodies. Leucism is a partial loss of pigmentation.
"Judging by the pictures, it's very close to albino, or leucistic," he said. "The genes that code for very white birds are in the area and could be turning up more often due to inbreeding."
Some situations make it easier than others to see Vancouver Island's white ravens, says Yip, who runs the site VancouverIslandBirds.com.
"Just after fledging, the raven family usually hangs around a location for a few weeks while the parents teach the fledglings survival skills. Sometimes the location is known and accessible to the public, and sometimes the location is unknown and sightings are just accidental. Last year the fledglings hung around a farm and the public was welcome to visit. This year there was no known location so sightings have been accidental and irregular."