For the Birds – Northern Finch Forecast

In the last column, I wrote about irruptive northern finches. In the past two weeks, birders across Maine have seen an influx of some of these birds. Common Redpolls, Pine Grosbeaks, Evening Grosbeaks, Pine Siskins, Red Crossbills and White-winged Crossbills have all been seen at multiple locations in the state.

I pointed out that two events must occur for significant irruptions to occur. First, the seed crop on the breeding grounds of these northern birds must be low, forcing the birds to move south for the winter. Second, our seed crops must be sufficient to provide for irrupting birds and allow them to stay. It is already clear that this will be a flight year for northern finches. Will we have enough seeds here to support the finches for the winter? We’ll have to see.

Ron Pittaway, an Ontario birder, gathers information on seed crops in eastern Canada and prepares a prediction for northern finch abundance. Some of the information Ron uses comes from eastern Quebec and the Maritime Provinces so his predictions can be applied to Maine with a bit of caution.

As one would surmise from the northern finches already arriving in Maine, seed crops in the boreal forests of Canada are poor this year. Last year by the way produced bumper crops of conifers in the boreal forest and northern finches were scarce as hens’ teeth here in Maine last winter.

Ron notes that in Ontario Pine Siskins and White-winged Crossbills departed east and west in the summer. This eastward movement may account for the good Pine Siskin numbers we have seen in Maine this fall. Bird counts in Ontario indicate that Evening Grosbeaks, Pine Grosbeaks, Purple Finches and redpolls (Common Redpoll and the much rarer Hoary Redpoll) are irrupting south from northern Ontario. Bring them on!

Pine Grosbeaks are unusual finches because they depend largely on soft fruit rather than seeds of conifers or other trees. Pine Grosbeak movements are triggered by failure of mountain ash (or rowan trees). Poor fruit set has occurred in the boreal forests of Canada. Irrupting Pine Grosbeaks look for crabapples, mountain ash berries and the fruits of various ornamental shrubs like cherries. They will also frequent sunflower seed feeders. We have not had a sizeable Pine Grosbeak flight since the winter of 2001/2002.

Purple Finches have been driven south out of northern Ontario by low conifer production. Ron Pittaway predicts that the Purple Finches will continue to move south into the mid-Atlantic states as fall gives way to winter. If he is right, enjoy those Purple Finches at your feeder while you can.

White-winged Crossbills are one of the most nomadic of the northern finches, wandering frequently in search of good cone crops. Once a bumper crop is found, these crossbills may stop and nest, regardless of the season. White-winged Crossbills are the only North American birds in which nesting has been documented in every month of the year. One of my most memorable birding memories occurred in the Northeast Kingdom of Vermont one January when I watched White-winged Crossbills feeding their young when the temperature was twenty below!

Pittaway notes that the favored cones of White-winged Crossbills, balsam fir and red spruce cones, are scarce throughout Ontario but abundant in Nova Scotia. My impression is that Maine crops of these two trees are good as well. Perhaps we will have a banner year for White-winged Crossbills.

Birch seeds, the favored food of Common Redpolls, are quite scarce throughout northern Ontario and Quebec. There is every reason to believe we will have an excellent winter for Common Redpolls this year.

Evening Grosbeaks depend on seeds from a variety of trees, most of which have a poor seed crop this year in the boreal forests of eastern Canada. We can expect an irruption but unfortunately nothing like the irruptions of 20 years ago. Evening Grosbeaks populations are declining and the likely reason is the decline of spruce budworms. Evening Grosbeaks rely on spruce budworm caterpillars and pupae for feeding their young. So the lack of major spruce budworm outbreaks has been great for spruce trees but unfortunate for Evening Grosbeaks.

Irruptions are also staged by Red-breasted Nuthatches and Bohemian Waxwings. Red-breasted Nuthatches depend on cone seeds for overwintering and not surprisingly have moved south (some as far as Georgia). They are pretty common in Maine now.

Like the Pine Grosbeaks, Bohemian Waxwings depend on mountain ash berries. The poor yield of these trees in the boreal Canadian forests is forcing these vagrants south and east. Good numbers have already been seen in Maine.

[Originally published on November 17, 2007]