The Finch Forecaster

From northern Ohio, Kenn writes: This Common Redpoll was outside our window a year ago, in December 2007. It was one of dozens that came to our feeder that month, and one of hundreds that we saw in the general area. This month, we haven’t seen a single one.

Redpolls are in the "winter finch" group, and they were the headliners last year. Common Redpolls (and a few of their pale high-Arctic relatives, Hoary Redpolls) were all over the central and eastern U.S. and southern Canada in the winter of 2007-2008. Pine Grosbeaks also moved south in good numbers. So did Red-breasted Nuthatches and Bohemian Waxwings, which are not finches but which are similarly erratic in their winter occurrences.

We used to talk about winter finch invasions being "unpredictable," but that’s not accurate. These invasions are caused by changes in the supply of natural wild food in the boreal forest of Canada and Alaska, and if we knew enough about what was happening there, we could make predictions about which finches would invade in a given winter.

In fact, there is someone who knows enough, who researches the situation every year and makes predictions about the finch flight. The dynamic duo of field ornithology in Ontario, Ron Pittaway and Jean Iron, are very well connected with scientists and birders all over the north. Every year in early fall, Ron Pittaway collects info about seed crops in the boreal forest and writes a prediction, focused on which birds will have a flight in southern Ontario and adjacent regions. All of us in the surrounding states and provinces wait eagerly for Ron’s forecast.

Knowing how tricky it is to gauge these things, it’s amazing how often Ron Pittaway is right on the mark. For the 2007-2008 winter, he predicted the big redpoll flight and the movements of Pine Grosbeaks, Bohemian Waxwings, and Red-breasted Nuthatches. For this winter, he predicted that Pine Siskins would mostly leave Ontario, and indeed we had a flood of them coming south through the Midwest this fall. He predicted the possibility of a widespread southward flight of White-winged Crossbills, and we’re all enjoying the reality of that now.

Does Ron have mystical powers? Well, yeah, but this is mostly just a result of detailed understanding of the birds and their food supply. This year, for example, Ron predicted that Pine Grosbeaks would stay in the far north because the mountain-ash berry crop was good there. He predicted that Pine Siskins would leave Ontario because the spruce cone crop was poor in that province. He predicted the White-winged Crossbill flight because spruce cone crops over much of Canada had fallen off from previous highs. It’s fascinating stuff; you can read the whole thing on the Ontario Field Ornithologists site here.

Happening Right Now: Crossbill Invasion

From Birding Central, Kenn writes: In the northeastern quadrant of the U.S. and adjacent southern Canada, this is shaping up to be a huge winter for northern invaders. I’ve written already about Pine Siskins invading southward, and that push is continuing, with flocks reported all over the east. Northern Shrikes have appeared in unusual numbers, and so have Snowy Owls, with many around southeastern Canada and the Midwest. Flocks of Evening Grosbeaks have put in brief appearances in several places. Now, just within the last few days, flocks of White-winged Crossbills have set the hotlines buzzing all over Ohio.

Of all the "winter finches," White-winged Crossbills are the most nomadic. They specialize on cones of spruces, hemlocks, and tamaracks, using their trademark crossed bill tips to pry open the cones and get to the seeds. The map here shows their overall range in North America -- but they are never present throughout this range at once. They concentrate where there are bumper crops of cones, nesting and raising their young where the food is abundant at practically any time of year. When the cone crop fizzles and the food supply declines, flocks of crossbills fly fast and far in search of the next good feeding area. The purple area on the map shows the limits of their year-round range; within those limits, the same birds might nest in Quebec one year, Alaska the next, Ontario a few months later, sweeping back and forth across the continent to find the cones.

The dashed blue line on the map shows the (very approximate) southern limit of their winter wandering. They certainly don’t come south to this line every year, or even once every five years. The classic setup for an invasion is to have a huge crop of spruce cones in eastern Canada, so that the crossbills nest and raise lots of young, followed by a crash in the cone crop in fall. When that happens, White-winged Crossbills may suddenly appear all over Ohio and surrounding areas -- as they have in the last few days.

A birder who knows the callnotes might detect these birds anywhere, the flocks passing overhead in rapid flight. To get a sit-down look at White-winged Crossbills, birders are seeking out places where northern evergreens have been planted. Parks and cemeteries with lots of hemlocks have been productive here. The crossbills appeared in the Cleveland area last Saturday, in Toledo on Monday, in Columbus today. There are probably hundreds more flying around that no birder has seen yet.

Siskin Attack!

From Oak Harbor, Ohio, Kenn writes: I heard it this morning, high overhead, a sound that I'd been waiting for. Distant but unmistakable, a mix of querulous rising notes and dry rattles. Scanning the sky, I picked up a flock of half a dozen small, short-tailed birds, in high, bounding flight. Yes, they were Pine Siskins, all right.

Every fall, birders over much of the U.S. and Canada keep an ear toward the sky, listening for the calls of "winter finches" flying overhead. The "winter finches" are a group of about nine species that nest in the far north or in high mountains and that are mostly vegetarian in their diet: they eat seeds, buds, berries, but relatively few insects, unlike most other songbirds. These "winter finches" are extremely variable in their winter distribution. If there's a good supply of food in their nesting range -- a good cone crop on the spruces, for example, or lots of seeds on the birches -- the finches may stay in the Arctic all winter. But if wild food crops fail in the far north, the finches may invade far to the south. Depending on the season, other northerners may move as well: Bohemian Waxwings, Red-breasted Nuthatches, various northern owls. No two winters bring exactly the same mix of birds, and birders living south of the boreal forest always wait with anticipation to see which of these winter invaders will make an appearance.

Pine Siskin is a member in good standing in the "winter finch" group. A few siskins come south every fall, but some years there are huge numbers of them. It looks like this might turn out to be such a year. Just within the last few days, we've had reports of Pine Siskins suddenly showing up all over southern Ontario, southern Michigan, northern Ohio. These birds over Oak Harbor this morning may be part of a major flight. We should know for sure within the next few weeks.