Snowy owls are moving into Iowa in near record breaking numbers this winter

Despite what can feel like Arctic weather sweeping into Iowa during the winter, the state still finds itself a long way from the Arctic tundra. So it would be surprising to find Arctic tundra wildlife soaring over Iowa’s picked corn fields or perching on the state’s telephone poles. But this winter seems to be an exception to that rule, because since early November reports of an iconic tundra-dwelling bird, the snowy owl, have been pouring in from all corners of the state.
Wildlife biologists call the phenomenon a “winter irruption,” and it has already yielded numerous sightings of this all-white, vulture-sized owl in Iowa this winter. The recipe for predicting when a winter irruption will occur is not well understood, according to Stephen Dinsmore, professor of natural resource ecology and management at Iowa State University. But there are a few consistencies in years with more sightings of snowy owls south of their typical range.
“In years with high lemming populations, breeding pairs of snowy owls can sense the increased food supply and quickly make the most of long Arctic days, laying clutches of sometimes more than 10 eggs and successfully raising their young on diets full of lemmings,” said Dinsmore. “In years when most of those young survive, conditions are prime for southward irruption. There become too many mouths to feed in the tundra and young owls are forced south to find food in less familiar landscapes like Iowa.”
Populations of the small, field mouse-like lemmings on the Arctic tundra are cyclical and they become abundant every few years before crashing as they literally eat themselves out of food. These regular cycles coincide with what typically produces snowy owl irruptions, although the magnitude of an irruption can vary.
Read the full story in the January 17 edition.