The North American Boreal Forest isn’t called “North America’s Bird Nursery” for nothing. This vast biome, stretching from Alaska to the Rocky Mountains and eastward to the Atlantic Ocean, contains some of the most extensive, intact ecosystems on Earth. Diverse landscapes of conifer forest, wetlands, and peatlands support 325 species of breeding birds and nearly half of the 700 bird species that regularly occur in the U.S. and Canada.
Each spring, between 1–3 billion birds migrate to the boreal biome to nest and raise their young. And each fall, 3–5 billion adult and young-of-year birds fly south to favored wintering grounds. Some of the more cold-hearty species winter in their breeding range or may descend to lower elevations in more mountainous regions. These “non-migratory” boreal species make occasional erratic movements southward in winter, usually in quest of food. These birds are the feature of today’s Dawn Chorus.
The phenomenon known as “irruption” is a dramatic, irregular migration of large numbers of birds where they aren’t commonly found, potentially at a great distance from their typical winter range. The main driver of bird irruptions is a lack of food in the birds’ normal wintering grounds. Poor seed crops of birch, maple, pine, spruce, or hemlock in boreal habitats can trigger irruptions of birds in the Finch Family. Some birds of prey may irrupt in banner nesting years or when rodent populations crash. Unduly harsh, cold, and severe weather may also push birds to more temperate wintering grounds.
Depending on the species, irruptions may occur in 2–10 year cycles, or they may be much more unpredictable. The winter of 2012-2013 saw a mass irruption called a “superflight” of Red-breasted Nuthatches, Red Crossbills, Pine Siskins, Evening Grosbeaks, Pine Grosbeaks, Common Redpolls, and Purple Finches deep into the U.S. Superflights are the stuff of birding legend: a once-a-decade event where climatological patterns and bird numbers combine to send six, seven, or eight northern species fanning out across the U.S.
What is a survival tactic for boreal birds can be a thrilling time for the birding community! Finding rare birds at feeders and favorite birding haunts is always a welcome surprise. Many avid birders check in with the Winter Finch Forecast, an annual forecast of finch irruptions curated by Ron Pittaway of the Ontario Field Ornithologists. Pittaway bases his forecast on availability of boreal forest seed crops. For winter 2018-2019 he provided this general forecast:
This is an irruption (flight) year for winter finches in the East. Cone and birch seed crops are poor to low in most of Ontario and the Northeast, with a few exceptions such as Newfoundland which has an excellent spruce crop. It will be a quiet winter in the North Woods. Expect flights of winter finches into southern Ontario, southern Quebec, Maritime Provinces, New York and New England States, with some finches going farther south into the United States. Stock your bird feeders because many birds will have a difficult time finding natural foods this winter. This forecast applies primarily to Ontario and adjacent provinces and states. Spruce, birch and mountain-ash crops are much better in Western Canada.
Pittaway then provides individual forecasts for eight irruptive finch species as well as Blue Jay, Red-breasted Nuthatch, and Bohemian Waxwing, and several links with detailed information on finch irruptions. Let’s take a closer look at these irruptive boreal birds:
Finches and Allies (Fringillidae)
Evening Grosbeak
A chunky and showy finch with a large, powerful, conical bill, thick neck, full chest, and shortish tail. Adult males are yellow and black with a prominent white wing patch and bright yellow stripe over the eye. Females and immatures are mostly gray with white and black wings and a greenish-yellow wash on the neck and flanks. Evening Grosbeaks are attracted to the seeds, berries, and buds of trees and shrubs, particularly maples. They show up irregularly at feeders in sizeable flocks, so platform feeders or hoppers stocked with sunflower seeds are best.
Pine Grosbeak
The Pine Grosbeak is a large, plump and heavy-chested finch with a round head, thick conical bill, and long slightly-notched tail. Males are decked out in pinkish reds and females are subtly yellowish-green. In winter, they’re often found in mountain-ash or crabapple trees gobbling up fruit, or in conifers, feeding on needles. Pine Grosbeaks frequently visit feeders during irruptions. Because of their size, large tube feeders, platform feeders, or large hoppers stocked with black oil sunflower seeds or hulled sunflower seeds are best.
Gray-crowned Rosy-Finch
The Gray-crowned Rosy-Finch is a medium-sized, chunky finch, dark brown overall with pink highlights on the belly, rump, and wings, and gray crowns. They are a western species of extreme environments, breeding in alpine habitats and wintering in open country, including mountain meadows, shrublands, cultivated areas, and rocky hillsides. In winter they can form huge flocks of up to several hundred birds feeding on grass and weed seeds. Gray-crowned Rosy-Finches will show up at feeders where they eagerly gobble up sunflower and nyjer seeds. Inspect flocks closely for presence of a few Black Rosy-Finch in the mix, especially in the Rocky Mountain region.
A huge flock of Gray-crowned Rosy-Finch foraging near Scotch Creek Wildlife Area in north-central Washington State. A freeze-frame review and sectional count of this flock revealed there to be over 1,000 birds. Just wow. YouTube video by Scott Ramos.
Purple Finch
Compared to small forest birds like chickadees, kinglets, and nuthatches, Purple Finches are large and chunky with powerful, conical beaks larger than any sparrow’s. Tail is short and clearly notched at the tip. Roger Tory Peterson described the Purple Finch as a “sparrow dipped in raspberry juice.” Males are delicate pink-red on the head and breast, brown on the back and cloudy white on the belly. Females have no red and are coarsely streaked below with a whitish eyestripe and dark line down the side of the throat. Purple Finches are irregular winter visitors to feeders and seem to like black oil sunflower seeds best, though they also feed on seeds of ash and elm trees, as well as weed and grass seeds, berries, and small fruits.
Common Redpoll
Common Redpolls are small songbirds with small heads and small, pointed, seed-eating bills. The tail is short with a small notch at the tip. Adult males have a red crown and pink-washed chest; females and immatures are brown and streaky with a small red patch on the crown. Redpolls travel in flocks of up to several hundred individuals, moving frenetically while feeding on birch catkins or weed seeds. Redpolls readily visit winter feeders stocked with nyjer seed (a high-energy oilseed from Africa and Asia) often resulting in feeding frenzies and best opportunities for close study. These tiny, energetic birds are remarkably cold-hearty, withstanding temperatures of -65° F by tunneling up to 12 inches into insulating snow. Examine redpoll flocks closely for paler, fluffier, and smaller-billed Hoary Redpolls, which may be present in very small numbers among flocks of Common Redpolls.
Red Crossbill
The Red Crossbill is a stocky, medium-sized finch with a crisscrossed bill designed to pry into tightly closed conifer cones to access the seeds. The head and body of adult males are deep brick-red to reddish-yellow or greenish, with black-brown wings and tail. Females are uniformly olive or grayish, with greenish or greenish-yellow chest and rump. Red Crossbills are seldom found away from conifers, which supply the seed cones that comprise its main food source. The species may wander widely to find good cone crops. Red Crossbills in North America show wide variation in bill shape, food specialization, and flight call types, with new research suggesting there may be as many as eight different species on the continent. Their ‘cousin’ the White-winged Crossbill is an uncommon and irregular winter visitor, but occasionally shows up on non-native spruces and European Larch.
Pine Siskin
The Pine Siskin is a very small finch with a sharp, pointed, and slender bill and short, notched tail. Adults are brown and very streaky overall with subtle yellow edgings on wings and tails. Flashes of yellow can be seen as they take flight or flutter wings. Pine Siskins are nomadic, ranging widely and erratically across North America each winter in response to seed crops. They are gregarious, foraging in tight flocks while calling incessantly. Pine Siskins readily home in to feeders, preferring nyjer, thistle, and other small seeds such as millet or hulled sunflower seeds. They may also eat suet. Pine Siskins are even more cold-hearty than redpolls, piling on half again as much winter fat as redpolls and ramping up their metabolic rates ≥40% higher than a “normal” songbird of their size.
Non-Finch Irruptives
Red-breasted Nuthatch
The Red-breasted Nuthatch is a small, compact bird sporting a long, pointed bill, very short tail, short, very broad wings, and almost no neck. They have a blue-gray mantle and strongly-patterned black-and-white striped face. Its underparts are rich rusty-cinnamon, paler in females. Although Red-breasted Nuthatch may breed well into the U.S., about 25% of the North American population breeds within Canadian boreal forests. In years when winter cone crops fail, they migrate in large numbers to more southerly forests. This species readily comes in to all feeder types offering black oil or hulled sunflower seeds, suet, peanuts, peanut hearts, or even mealworms.
Bohemian Waxwings
The striking Bohemian Waxwing is a full-bellied, thick-necked bird with a shaggy crest atop a small head. They are grayish brown overall with a delicate peach wash around a black mask. Wings have two distinct white rectangular patches and red wax-like tips on the secondaries. Undertails are rusty and the tail is tipped in bright yellow. The bohemian wanderings of this waxwing are renowned. They make occasional erratic movements southward in winter due to shortages of fruits and berries in Canada’s boreal forest. Highly social, Bohemian Waxwings usually move about in tight formations, descending en masse on mountain-ash or crabapple trees, quickly stripping them of fruit. Since such plantings are typically around buildings in cities and towns, large flocks with their buzzy, twittering calls may be observed in urban areas of northern towns. They may eat fruits set out on platform feeders, but the best way to attract them is to plant fruit-bearing trees or shrubs that hold fruit late into the fall and winter.
Rough-legged Hawk / Snowy Owl
Raptors that feed on small mammals with cyclic population fluctuations are another group of irruptive species from the boreal biome. Among North American species, Rough-legged Hawk and Snowy Owl appear to irrupt with about a four-year periodicity, reflecting a recognized four-year cycle among tundra and grassland rodents. However, researchers suggests it’s not hunger producing Snowy Owl irruptions, but rather an absurd abundance of lemmings and voles fueling unusually large clutches and highly successful breeding seasons for the owl. A banner reproduction year in the summer of 2013 led to a Snowy Owl mega-irruption in winter 2013-2014, the largest irruption in the Northeast and Great Lakes regions in a century with birds reported as far south as Florida and Bermuda. A smaller irruption of Snowy Owls occurred in 2017-2018. The best way to find out if Snowy Owls or other irruptive raptors including Great Gray Owl, Short-eared Owl, and Gyrfalcon are being spotted near you is to check eBird using a species search. You might also want to check in with your local Audubon Society chapter.
Bird irruptions can certainly add excitement to winter birding. Why not put out the welcome mat for these boreal wanderers? Project Feeder Watch has a great online list of Food and Feeder Preferences of Common Feeder Birds for almost 100 birds including all of the species featured in this diary (except raptors). If you’re successful bringing in finches by the flockful, be sure to take extra precautions to prevent the spread of bird diseases such as Salmonellosis. Cleaning bird feeders and bird baths regularly is essential to help keep irrupting birds and your usual backyard flocks healthy.
The platform feeder is now open for your reports of birdy happenings in your neck of the woods, mountains, coast, desert, prairies, swamps or wherever you’re wintering!