Each year, certain migratory birds in North America make the trip south to their wintering grounds. This journey takes place every year in roughly the same pattern. So much so, that one can almost plan their calendar according to the arrival and departure of a certain species. However, there is another migration that takes place in a much different way: the winter finch migration.
Winter finches reside in the northern forests of Canada during summer and often move around in fall and winter. However, they don’t migrate in the same patterns as other bird species. In fact they don’t even repeat the same pattern from one year to the next.
The term “irruption” is often used to describe mass migrations of some of these northern species into the United States. In years past, birders have noticed increased numbers of certain winter finch species (Inlcluding Crossbills, Evening Grosbeaks, Pine Siskins and more) in some winters, while in other winters, North America’s conifer forests stand untouched by these birds.
Part of the mystery of winter finches is that for the longest time, it was unclear which species would irrupt (if any) on a given year and what the cause was for these large flights of birds moving across the continent. It turns out there is actually a singular driving force to the movements of these birds: food.
The best way to predict which winter finch species are going to be moving south is by analyzing each species preferred food source in the north. In particular, many of these birds feed on conifer cones. When cone crops are low, these nomadic birds migrate to other areas in search of food. Enter the winter finch forecast.
Each year experts (originally Ron Pittaway and now Tyler Hoar of Ontario Field Ornithologists) put together a detailed picture of which northern conifer crops are high and low in Canada, and therefore which finch species are expected to irrupt and move into the United states. What is particularly interesting about these finch species is that each one seems to prefer a different type of conifer seed as its dietary staple. Thus, understanding the movements of a particular species is somewhat of a scientific art form. This report has become an annual treat that is highly anticipated by birders excited by the prospect of seeing these colorful birds dotting the winter landscape.
The winter finch forecast usually comes out in the middle of September and provides an excellent sneak preview of what to expect as far as the types of birds you’re likely to see come fall and winter. You can find this exciting report by going to the Finch Research Network , joining the finches, irruptions, and mast crops Facebook group, or by waiting until someone in your local birding community posts it.
Note: In addition to the winter finches, the forecast also includes clues to other irruptive and nomadic species too such as Red-breasted Nuthatches and Bohemian Waxwings.