Country Ecology: Northern shrike

Every few years, we are invaded by Northern shrikes. These large-headed, ferocious birds come down from the subarctic, where they normally hunt rodents and insects in the boreal forests of Canada. During their summer breeding months, shrikes prey on lemmings, voles, and other small animals.

But when they come down after a population crash of these critters, they turn on our resident songbirds. Meadow voles are not available, running around in their tunnels below our wintry snowcrust. The shrikes would eat them if they could but will never encounter them in their safety of subterranean snow burrows.