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What Is A "Superflight"?

What Do We Mean By "Invading"?

Where Were They Going?

Was the 1997-98 Irruption More Significant for Some Winter Finches Than Others?

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Where Did These Invaders Come From?

Both Hoary Redpoll and Common Redpoll typically remain the entire year in arctic Canada and Alaska. Pine Grosbeaks breed in upper elevations of the Rocky Mountains to northern Canada and Alaska; White-winged Crossbills, in Canada and the extreme northern United States. The breeding range of Pine Siskin, Purple Finch, and Evening Grosbeak extends through the northern U.S. and central Canada. Red Crossbills breed at high elevations across the U.S. and Canada; Red-breasted Nuthatch, from Newfoundland and Labrador south through New England and through the Appalachian Mountains to Tennessee. Most of these species migrate south to some degree every winter, but the extent of this movement is highly variable. In fact, one of these species may invade during a particular year while the others remain virtually absent. Pine Siskins, for example, irrupted into the Appalachian and Central Plains regions in unprecedented numbers during the 1987-88 winter season; that same year, there were few reports of the other northern finch species.

In western North America, birds that breed in the mountains may irrupt to lower elevations. However, this movement does not seem to correspond with winter finch invasions from northern Canada. Last winter, Mountain Chickadees irrupted from higher elevations down into areas such as the plains of Colorado, and Red Crossbills were reported by Project FeederWatchers in the west in extraordinary numbers. Yet the 1996-97 season was not an invasion year for northern winter finches.