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Irruptive Species: Which Ones Will We See This Winter?

One of the pleasures of winter is to watch for unlikely birds visiting the Pacific Northwest and the Eastside of King County.

By Andy McCormick

Photos (Top to bottom): Snowy Owl, Evening Grosbeak, and Pine Siskin, by Mick Thompson

Snowy Owl, by Mick Thompson“Irrupt” means “to undergo a sudden upsurge in numbers especially when natural ecological balances and checks are disturbed” (Merriam-Webster).

In the United States, irruptive bird species are those that winter farther south than they normally do. Reasons vary as to why we see more of a particular bird species in one winter than in another.

Here for the Food

Sometimes it can mean there is a harsher winter than most in the northern latitudes, making it difficult for birds to find food.

Sometimes it can mean there are too many birds up north. A species may have had an abundance of food in summer, enabling more offspring to survive into the winter to compete for food that is more limited then. Birds may move until they find an adequate food supply to sustain them.

What to Watch For

Here is a list of some of the most common winter irruptive species in the Pacific Northwest:

Snowy Owl Two winters ago the Pacific Northwest saw so many Snowy Owls that they seemed commonplace. They were seen all across Washington and into Oregon. One was even seen in Hawaii!

Last year a Snowy Owl irruption was seen in the Eastern United States. These magnificent birds are always welcome in winter.

Evening Grosbeak, by Mick ThompsonEvening Grosbeak This is a very nomadic species by nature, typically “seen one day and gone the next.” In winter they have to forage farther afield for seeds, so in some years we can see many more than usual.

Pine Grosbeak Already a number of Pine Grosbeaks have been seen this fall on the Olympic Peninsula. This species is not as well known as the Snowy Owl, but birders love to see it in Washington. We may see more as the winter progresses.

Red Crossbill Last winter was a busy one for Red Crossbills. There were so many of them in Washington that flocks were feeding on Douglas fir trees in Seattle and near downtown Bellevue.

White-winged Crossbill This is a very uncommon bird to see in western Washington in any year, but one was seen during the Eastside Audubon Christmas Bird Count in 2013. Join a CBC team, and maybe you’ll find an irruptive bird this year, too.

Pine Siskin, by Mick ThompsonPine Siskin To the surprise of many birders, Pine Siskins were very hard to find last winter. They just seemed to stay north all year. This fall some are being reported at feeders and in small flocks, but large numbers are not here yet. They love feeders.

Common Redpoll This northern finch was very prominent in western Washington two winters ago. A good-sized flock was seen almost daily through the winter at the Lake Hills Greenbelt in Bellevue. One bird was suspected of being a Hoary Redpoll and created a stir of excitement, but the Washington Bird Records Committee of the Washington Ornithological Society (WOS) concluded that there was not enough evidence to recognize that sighting.

Wishing You a Rarity

Watching for irruptions of bird species is a great winter birding sport. Take a second look at what looks like a common bird: You may be surprised.

If you can photograph a rare bird, you'll have a greater chance that the WOS records committee will agree with your sighting.

Enjoy our winter birds, whether they are rare or common! They’re all part of our Northwest winter.

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The mission of Eastside Audubon is to protect, preserve and enhance natural ecosystems and our communities for the benefit of birds, other wildlife and people.