Every few years, great grey owls move—usually en masse—from their boreal breeding grounds, typically in search of food. The last great irruption (as these movements are called) happened five years ago, in 2004-2005. It was so large that it caught the attention of bird lovers, environmentalists, and the mainstream media.
As freelance writer Frances Backhouse writes, “Like many ghosts, they are notoriously hard to track down, even by dedicated seekers who are willing to venture into the boggy, mosquito- and black fly-ridden places that are the owls’ preferred nesting sites throughout most of their range. But now and then, in the dead of winter, they materialize in unexpected locations far from their usual breeding range, thrilling keen birders and casual observers alike.”