Thursday, November 03, 2005

Winter Finches

Irruptions of winter finches can be difficult to predict. When speaking of "winter finches," one commonly means those species of finches that breed far north in the boreal forests and then move south for the winter. (Cornell has a summary of the species involved.) Because these movements are somewhat irregular, they are frequently called "irruptions." Some species, such as the purple finch, American goldfinch, and pine siskin, can be expected to come south in most winters. Others, such as the redpolls, grosbeaks, and crossbills, are much rarer south of Canada.

The useful eBird site has provided a winter finch forecast for the coming winter by an ornithologist from Ontario. He bases the predictions on assessments of food availability in the boreal forests. The prediction is for a relatively good migration this year, though it varies from species to species. One species of interest to me is the pine siskin, which I see rarely even though it is not particularly rare in the northeast. It seems to look good for a siskin invasion in the northeast:

Pine Siskin: There are very few conifer seeds to hold siskins in the boreal forest and Algonquin Park this winter. Siskins are now moving south through southern Ontario. Most will be elsewhere in North America this winter. Any siskins remaining in southern Ontario this winter will be at feeders where they prefer nyger seed.
Perhaps this will be the year I see my first DC siskin. Another "most-wanted" species for me is the common redpoll, which I still have not seen. It is not looking so good for a southward movement of that species this year:
Common Redpoll: When redpolls winter in the boreal forest they prefer birch (Betula) seed. Since white birch seed crops are average to good in many parts of northern Ontario, I expect many redpolls will stay north this winter. However, some redpolls likely will wander south in mid-winter as seed supplies diminish. Watch for them at feeders where they feed with goldfinches on nyger seed. Redpolls and most winter finches wander more widely than is generally realized. For example, Barry Kinch of the Mountain Chutes Banding Station near Elk Lake in northern Ontario banded a Common Redpoll on March 4, 2001, that was found dead a year later on March 24, 2002, in Kimberly, British Columbia, which is a straight line distance of 2,611 kilometers west.
Another winter finch, the evening grosbeak, appears to be in decline, and its movements are harder to predict:
Evening Grosbeak: This has been a mystery species in recent years. Where are the flocks of "greedies" that crowded feeders 25 years ago? The decline is real. Kelling (1999) analyzed Christmas Bird Counts from 1959 to 1998. Numbers of Evening Grosbeaks were stable or increased until 1980 when numbers began to decline. The rate of decline increased between 1990 and 1998 with the Northeast and Great Lakes regions having the steepest declines in winter. Recently, Bolgiano (2004) provided the most plausible explanation for the decline. He found higher numbers during outbreaks of spruce budworm and lower numbers after outbreaks ended. Evening Grosbeaks feed heavily on budworm larvae and the larvae are fed to young. Evening Grosbeaks began to decline in 1980 after the last major outbreak of spruce budworm during the 1970s. Evening Grosbeaks coming into southern Ontario will find a good crop of samaras (keys) on Manitoba Maples and an abundance sunflower seeds at feeders.
An evening grosbeak and white-winged crossbills have already been reported in New Jersey:
Other sightings in Sussex County were of a GOLDEN EAGLE over Culver's Gap Oct 31, 8 WHITE-WINGED CROSSBILLS over Sunrise Mountain Oct 28, and an EVENING GROSBEAK at a feeder in Wantage Twp Oct 27.
I would recommend reading the entire article posted at eBird, at least for anyone interested in the winter finches, because it does have some interesting information. It also has migration information on three non-finch species, including the lovely red-breasted nuthatch. On the latter, the author writes:
However, this year only a small number of Red-breasted Nuthatches moved through southern Ontario in September and currently they are scarce in Algonquin Park and the boreal forest of northeastern Ontario. Where are they?
Well, it appears that they moved substantially south, as they were popping up at feeders and in pine groves across the mid-Atlantic region over the past week.

Update: Nuthatch has more information on the decline of evening grosbeaks.