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    Green Acre Radio: The snowy owl mystery

    On Port Susan Bay, there are thousands of regular visitors among the bird populations. But, in a rare event, there are also snowy owls.

    A snowy owl stops on a sign along a jetty in Missouri during December 2011.

    A snowy owl stops on a sign along a jetty in Missouri during December 2011. Howard Arndt via U.S. Army Corps of Engineers (Kansas City District)/Flickr

    A female Snowy Owl’s brood patch is visible as she returns to the nest.

    A female Snowy Owl’s brood patch is visible as she returns to the nest. Paul Bannick

    This winter the region is hosting a mysterious and nomadic visitor. It hails from the  Arctic, has been immortalized throughout history, and was one of the first species to be cast in the movies of Harry Potter. What is it and why is it here?

    Click on the audio player above or here to listen.

    We’re looking for an unexpected winter visitor. It has pointed wings that span 50 inches and large yellow eyes. Adults are mostly white. Juveniles marked with subtle dark barring. A grassy expanse of wetland on Port Susan Bay west of Stanwood is the perfect spot. There are thousands of wintering birds here, Northern Harriers, Red-Tailed Hawks, Blue Herons, Snow Geese, Marsh Wrens. Adam Sedgley with Seattle Audubon spots a hawk. “It looks like it’s just about ready to land.” A smaller bird takes off. “That little kind of choffing call. Churp. Churp.” It’s a short eared owl. We’re getting closer to the species we’re looking for. “I think I found one. It’s quite far. I have to zoom in on my scope just to be sure. Yup. A snowy owl.” I take a look. “It’s much much bigger than I thought and you never would expect to see an owl sitting on the ground. Wow.”

    Hunkered down in an open field of yellow grass, a juvenile snowy owl has found hunting ground. The grass is as close to the artic tundra where it breeds as it gets around here. This winter is proving to be an “irruption year”, where an unusual number of nomadic snowy owls fly south from their breeding grounds in the Artic in search of food. Lemmings are their diet of choice. Research suggests when there’s a boom in lemmings, more owl chicks survive.

    But it doesn’t solve the entire mystery of why so many snowy owls have been seen throughout  southern Canada and northern US. Ornithologist Dennis Paulson. “They’re not spread all across the Arctic in the same cycle. They’re different cycle and different populations.” Lemming populations in any given area of the Arctic may skyrocket and then plummet precipitously. Two theories are at play. When there’s a spike in lemmings there’s an excess number of chicks or there are too few lemmings going into winter. Both force owls to hunt in new territory. What isclear is when there’s an abundance of lemmings, owls breed. Females may produce as many as eleven chicks. “The male starts catching lemmings and delivering them to the female or delivering them to some conspicuous place like a rock and if there are enough lemmings for him to catch in a certain number of days then this somehow stimulates her hormones and she prepares for breeding.”

    But other factors could impact snowy owls' ability to breed. Paul Bannick is author of the The Owl and The Woodpecker: Encounters With North America’s Iconic Species. He’s studied and photographed snowy owls in the Artic. “One of the impacts of climate change is that habitats move north and they move up in elevation. You have to move up or north to find an equivalent habitat. Well if you live on the top of the world there’s nowhere else to go.” Shrubs are starting to invade the otherwise arctic tundra. Snowy owls require tundra to make nests on small mounds. “If shrubs start to invade the tundra it changes that habitat and the first thing that changes is the lemmings have a less than ideal habitat.”

    More rain is making the tundra wetter. Permafrost and ice floes are shrinking making it difficult for lemmings to survive. In addition, new studies show snowy owls are more of a marine species than previously believed, says Bannick. Females will settle on ice floes for several months each year, “where they’re feeding on sea birds and we don’t really know yet what would happen if we didn’t have that sea ice. Where would the females go? Would it change their reproductive succerss? We don’t know the answers to that.”

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