Our feeders here in Waterville are being overrun by purple finches. Although purple finches nest in Maine, their population can swell in the non-breeding season by finches from elsewhere. Of course, there are some winters where our purple finches depart and we have to without these cheerful birds.

Have you noticed a relative dearth of the raspberry-breasted males at your feeder? The brown females with their bold white stripe above the eyes seem to dominate our feeders.

However, it is virtually impossible to tell adult females from first-year birds in the field. A good percentage of the “female” purple finches are actually first-year males. Next summer, these young males will sport the purple head and breasts of older males.

Purple finches belong to the group of birds we call the northern finches or irruptive finches. These are birds of the boreal forest and taiga that may winter on their breeding grounds if the seeds on which they depend are plenteous. In other years, poor seed crops force them south to the delight of birders where these species don’t occur every year.

Poor seed production forces the birds to erupt (move out) of their nesting areas for the winter and irrupt (move into) areas where food can be found.

So, this year looks like an irruption year for purple finches. They may well push well south of us. I remember occasionally seeing irruptive purple finches in North Carolina when I was a lad.

Red crossbill abundance varies wildly in Maine. Some nest regularly in the northern forestland and mountains of Maine. They depend on large conifer cones like white pine. Their crossed bill is the just the ticket for scissoring apart the overlapping scales of a cone so that the seed can be extracted.

Throughout much of their range, red crossbills are nomadic, wandering widely in search of a good seed crop. They typically nest from late January to early April, feeding on the seeds from conifer cones that opened in the fall, and from early July to early September, feeding on seeds from newly formed cones. A good conifer set doesn’t guarantee Red Crossbills in your neighborhood but a bad seed set guarantees you will not see these wandering opportunists.

We had a nice influx of red crossbills into central and southern Maine late this summer, south of their typical range. Breeding was confirmed in Augusta and at four sites in western Oxford County.

Perhaps, these red crossbills will stick around for the winter but you never know with crossbills.

We are seeing what I hope will be a strong irruption of pine siskins. Large flocks have been seen in early October in Gardiner, Harpswell and Bangor. Siskins depend on smaller cones like those of eastern hemlock and tamarack for most of their energy.

For many years, Ron Pittaway in Ontario has been producing an irruptive finch forecast based on the abundance of cones and other seeds. Some of the birds that irrupt into Maine originate from eastern Ontario so his forecasts are always of interest to New England birders. Ron has passed the torch to Tyler Hoar.

A couple of Tyler’s predictions have already come true: the irruptions of purple finches and red crossbills. We’ll review his take on some other species.

Pine grosbeaks are unusual finches in that they rely on fruit, particularly mountain ash berries. The berries of these trees are abundant to our north so sadly we will likely not see  a pine grosbeak invasion this winter.

Common redpolls and hoary redpolls specialize on birch seeds. COVID19 restrictions have limited travel to the northerly breeding areas of these species so we don’t have a good handle on the swamp birch production there. A bit farther south, paper and yellow birch seed production is poor so we’ll keep our fingers crossed for a redpoll winter. Fill your thistle feeders!

Herb Wilson taught ornithology and other biology courses at Colby College. He welcomes reader comments and questions at whwilson@colby.edu

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