Forecasting the Winter Finch Flight

Oct 10, 2018

A Red Crossbill in Wellfleet
Credit Mark Faherty

The incredible hit-parade of off-course birds from the Western US continued this week, with sightings of Western Kingbirds from High Head in Truro and Lark Sparrow and Bell’s Vireo at Fort Hill in Eastham. But instead of these actual birds, I’m more in the mood to talk about theoretical birds – the predicted influx of the so-called “winter finches." How do I know they’re coming? Because I read the Winter Finch Report, of course.

The winter finches are a loose collective of northerly nesting songbird species, most of which are indeed finches related to the House Finches and goldfinches that clean out your bird feeders. They include the crossbills, the redpolls, Pine Siskins, Evening and Pine Grosbeaks, and Bohemian Waxwings, which are not really finches. These birds breed in the vast, cool boreal forests that cover much of the northern latitudes of the planet. What the different species have in common is a dependence on the cones, seeds, and fruits of various boreal trees for food. When crops of these trees they fail, the birds pick up and move. This strategy of completely leaving their breeding range and invading new areas at unpredictable intervals is knowns as “irruption." This doesn’t mean they have a volcanic temper – “irruption” is spelled with an “i” in this case.

It’s hard to know when and where they will turn up, but a Canadian birder named Ron Pittaway has taken on the task of trying to forecast the winter finch flight each year. He checks in with his network of foresters, biologists and birders throughout the boreal regions of Canada each late summer to assess spruce, birch, and mountain ash seed and fruit crops, and to get word of any early season movements of indicator species like Red-breasted Nuthatches and crossbills. He puts all of this information together in his annual “Winter Finch Forecast." Birders read the Winter Finch Report like my people read the obituaries – it’s must read material.

This year Ron is predicted a general winter finch irruption out of the boreal forests and into southern Canada and at least as far south as the northern tier of states. Crops of spruce and birch are low to our north, which will bring Pine Siskins, redpolls and hopefully White-winged Crossbills south into our area. Fruit crops of the different mountain ash species are also low, meaning we may see some Bohemian Waxwings – these are the bigger, more colorfully patterned cousins of our more familiar Cedar Waxwings.

Look for them this winter on fruits like ornamental crabapples, winterberry, and the invasive multiflora rose. As you might have noticed at your bird feeders, we have already seen an influx of Red-breasted Nuthatches this fall, which bodes well for our chances of seeing the other species. And Purple Finches have already been passing through in higher than usual numbers – watch your feeders for the distinctive females with their much bolder facial pattern than your usual House Finches. Later on, watch for siskins and redpolls on your niger seed, maybe hiding among your goldfinches.

As you watch your feeders for these mysterious northern wanderers this winter, consider reporting your sightings to Cornell’s project Feederwatch – data from this vast citizen science project has been used in many a peer reviewed study. And, as always, if you see anything really good, please report it to me.