Bohemian Waxwings, Pine Grosbeaks & other boreal irruptives on the move!

Matthew Medler, Boreal Songbird Initiative

Although wintry weather is just barely upon us, birders in northern border states from Minnesota to Maine are already enjoying one of the occasional joys of winter birding--an influx of boreal irruptive species like Bohemian Waxwing, Pine Grosbeak, Evening Grosbeak, and Common Redpoll. In New York alone, both Pine Grosbeak and Common Redpoll, usually the two latest species to appear during an irruption year, were reported before the end of October, and Bohemian Waxwing was seen on a record early date. The early arrival of these species, and the numbers in which they are being seen, suggests that we could be in store for a major irruption year, with some boreal species approaching the southern limits of their irruptive ranges. In fact, the early fall months have already seen a sizable irruption of Red-breasted Nuthatches, Purple Finches, and Pine Siskins out of Canada's boreal forest to areas as far south as Georgia. Below we summarize the current status of several boreal irruptive species, and suggest the extent to which they could be found if this winter does prove to be a major irruption event.

The Boreal Forest Region, covering 1.5 billion acres of Canada and Alaska, regularly hosts more than 300 species of birds, but perhaps none are more closely associated with this region than the group of winter finches and associated boreal irruptive species that includes Northern Shrike, Red-breasted Nuthatch, Bohemian Waxwing, Pine Grosbeak, Purple Finch, Red Crossbill, White-winged Crossbill, Common Redpoll, Pine Siskin, and Evening Grosbeak. With the exception of Red Crossbill, the Boreal Forest Region supports at least 25% of the North American breeding populations of all of these species, and in the cases of Bohemian Waxwing, White-winged Crossbill, and Pine Grosbeak, is home to nearly the entire continental populations. These three species, together with other northern boreal birds like Northern Shrike and Common Redpoll, will undoubtedly benefit from the recent announcement from the Canadian government that it will protect 25.5 million acres of boreal forest in the Northwest Territories. This land conservation agreement, one of the largest in North American history, will protect an area approximately 11 times the size of Yellowstone National Park.

While the exact mechanism of irruptive movements is not entirely clear, populations of all of these species periodically move southward out of the boreal forest, presumably in response to shortages of seeds, berries, and other important winter food sources. Some species, like Red-breasted Nuthatch, show a fairly regular pattern of irruptions every other year, while Pine Grosbeak irruptions occur less frequently, at intervals of five to twenty-five years. The large number of sightings of many boreal irruptives suggests that this winter is going to be an exciting one for birders, and a great opportunity to contribute important information to eBird! Here is a species-by-species summary of the boreal irruptives currently showing significant movements into the northern United States, and, in some cases, beyond:

RED-BREASTED NUTHATCH This species provided the first hint that we might witness a major boreal irruption in 2007, as individuals were reported from the barrier beaches of Long Island, New York in June and early July. Since that time, nuthatches have been reported from areas across eastern North America where the species does not usually occur--from Kansas and Iowa south to Texas and Louisiana, eastward through the Gulf Coast states, and northward along the Atlantic seaboard to New Jersey. A comparison of eBird fall migration maps from 2006 and 2007 shows the widespread nature of this species along the Atlantic Coastal Plain as it has irrupted southward this fall.

PINE GROSBEAK Pine Grosbeaks are making their first major irruption into the northern U.S. in several years, delighting a whole new generation of birders who are now seeing these large finches for the first time. Grosbeaks have been reported from across much of New York and the northern New England states (Vermont, New Hampshire, and Maine), with the number and widespread distribution of Vermont records being particularly impressive. Initial reports were of a few individuals at a time, but Pine Grosbeaks are now being seen in some places in flocks of 20 to 40 birds, with several spectacular adult males mixed into these flocks. Small numbers of grosbeaks have also been reported in northern Minnesota, Wisconsin, and Michigan. Recent reports of flocks of up to 25 Pine Grosbeaks in Massachusetts offer hope that Pine Grosbeaks will continue to move southward into states such as New Jersey, Pennsylvania, Ohio, Indiana, Illinois, Iowa, and South Dakota, where the species can occur during major irruption years.

BOHEMIAN WAXWING This species has been seen in good numbers in portions of Maine, New Hampshire, Vermont, and northern New York since late October and early November. Most of these sightings were of pure flocks of Bohemian Waxwings, with some groups containing in excess of one hundred individuals. In the Upper Midwest, there have been scattered reports from northern Minnesota, Wisconsin, and Michigan. During major irruption years, this species can be found as far south as northern New Jersey, Pennsylvania, the northern portions of Ohio, Indiana, and Illinois, and south to Arkansas and Oklahoma. In these areas, Bohemian Waxwing is most likely to be encountered as a scattered individual mixed into a flock of Cedar Waxwings. A few individuals have already trickled southward in New York and Massachusetts, perhaps boding well for points further south.

EVENING GROSBEAK Evening Grosbeak populations have plummeted in the past forty years, with National Audubon Society reporting a 78% decline in this species in its recent Common Birds in Decline report. While the days of abundant Evening Grosbeaks may be a thing of the past, there have been some mildly encouraging signs this fall from the Northeast, where this species has been reported more frequently and in greater numbers than in recent years. Unlike the more northerly Pine Grosbeak, Evening Grosbeak can irrupt as far south as central Texas and the northern portions of other Gulf Coast states. Sightings from southern New Jersey, southeastern Pennsylvania, Maryland, and Delaware could foreshadow a further push into the southeastern U.S., and recent reports from Ohio, Indiana, and Missouri are also encouraging.

COMMON REDPOLL This small finch is often portrayed as the most predictable of the boreal irruptives, as it demonstrated a consistent biennial pattern of irruption into the United States on Christmas Bird Counts throughout the 1990s and early 2000s. This pattern has broken down a bit during the middle part of this decade, but all indications in the field point to a sizable redpoll irruption during the winter of 2007-2008. Redpoll reports have come from across much of New England and New York throughout the month of November, including an impressive total of 400 in northern New York just before Thanksgiving. The species has been reported fairly frequently in Michigan, northern Wisconsin, and near Duluth, Minnesota, and individuals in this region are now venturing further south, into northern Illinois and Indiana. During a good irruption year, Common Redpoll can occur as far south as North Carolina, Tennessee, Arkansas, Oklahoma, Colorado, and Utah.

PURPLE FINCHPurple Finch nests further south than many of the other boreal irruptives, with the species regularly breeding across New England, New York, Pennsylvania, the northern halves of Michigan, Wisconsin, and Minnesota, and at higher elevations in the southern Appalachian Mountains. Observers in northern states began reporting Purple Finch with increasing frequency in late August and early September, as numbers were augmented by an influx from breeding populations in Canada. Since October, however, this species has begun vacating the northern United States and moving into southern states such as the Carolinas, Georgia, Tennessee, and Arkansas.

PINE SISKIN While perhaps not as flashy as many of the other boreal irruptives, no winter finch can be enjoyed by more birders than the Pine Siskin. During irruptive years, boreal populations of this species can be found across much of the eastern United States, while other populations cover much of the western half of the country. This fall, siskins are more widespread in the East than they have been since at least 2004.

NORTHERN SHRIKEPerhaps due to the large-scale movement of irruptive songbirds--potential prey items--out of the Boreal Forest Region this fall, Northern Shrikes have been reported in greater abundance than any other fall in the past five years. Reports from West Virginia, Ohio, Indiana, Illinois, and Missouri are all at, or in some cases, even slightly beyond the normal irruptive limits of this species. Unlike some of the other boreal irruptives, which are occurring in greatest densities in the Northeast, the Northern Shrike has been observed most frequently this fall in eastern Washington and in Minnesota and Wisconsin, highlighting its broad winter distribution across the northern U.S.

For More Information:
Are you curious about which of these boreal irruptive species is most dependent on the Boreal Forest Region? Are you aware that Canada's boreal forest is facing large-scale industrial development in the near future? And would you like to know what you can do to help conserve North America's Bird Nursery? If so, visit the Boreal Songbird Initiative and sign up for BSI E-Updates to learn more about the boreal forest, the birds that depend upon it, and the impact that Americans can have in helping conserve it.

For more detailed information about boreal irruptive species and all of the continent's bird life, subscribe to the Birds of North America Online. This comprehensive resource includes information on distribution, breeding, migration, habitats, and behavior for over 700 different species of birds that breed in Canada and the United States. The accounts include photos and audio selections for all species covered. Right now, BNA on-line subscriptions are being offered to eBird volunteers for the discounted rate of $25 for one year or $50 for two years.

Since 1999, Ron Pittaway of the Ontario Field Ornithologists has produced a 'Winter Finch Forecast' that predicts the winter status of finches and other boreal irruptive species. The focus of these forecasts is the status of winter finches in Ontario, but the predictions in these reports are applicable across a broad geographic area. In addition, the forecasts contain valuable information on food availability across boreal Canada, helping to explain the predicted movements of irruptive species. The Ontario Field Ornithologists' web site contains Ron Pittaway's 2007-2008 Winter Finch Forecast as well as an archive of previous years' forecasts.