By GENE BULLOCK
For Kitsap Week

Over the last 50 years, more than 60 percent of our bird species have shifted their winter ranges further north with the warming climate.

It’s one of the findings reported by National Audubon in a groundbreaking study of the effects of climate change, released last year. Shifts in ranges usually happen in increments over many seasons, but sometimes a dramatic change is linked to a single chance event.

In the 1970s, 50 Eurasian collared doves escaped from a pet shop in the Bahamas as the result of a burglary. The population soon spread to Florida, and today they are seen at backyard feeders all over the U.S. Listen for their three-part cooing call — ka-COO-COO.

The barred owl is an Eastern species that has spread across Canada and down into Western Washington. In the last 10 years, they’ve taken over in our area and turned into a serious threat to smaller owls and the spotted owl.

Snowy owls often show up here in the winter, but every four years or so we get an invasion, and the owls are seen in unusual numbers all over the state. Last year, the Northeast and Great Lakes had a record influx of snowy owls. The most likely explanation is a wide swing in the lemming populations in the Arctic tundra where the owls normally nest.Fifteen years ago, Western scrub jays were a rarity in Western Washington, but they now nest as far north as British Columbia.

When lemming populations explode, the owls may be all too successful in raising young. But in following years, the food supply may not be as abundant, and the area experiences a superabundance of young owls competing for limited food and breeding territories. When that happens, many are pushed south in search of food and unoccupied territories.

Washington had a big invasion of snowy owls during the winter of 2011-12.

— Gene Bullock is newsletter editor of Kitsap Audubon and birding columnist for Kitsap Week. Contact him at genebullock@comcast.net

Above, Eurasian collared doves escaped from a pet shop in the Bahamas in the 1970s, and are now becoming common throughout the U.S. John Oleyar / Kitsap Audubon