The year 2020 will be remembered for a lot of reasons, but for birders across the country, one of them will actually be good: the biggest irruption of northern finches in recent history. This year has seen huge movements of these birds southward, and many have reached astonishing places far from where you’d expect to find them.
Finch researchers are calling this year a “superflight,” where every species of boreal finch is irrupting, or moving southward in search of food. A perfect storm of feast and famine appear to be driving this banner finch year, affecting Common and Hoary Redpolls, Evening Grosbeaks, Pine Grosbeaks, Pine Siskins, Red and White-winged Crossbills, and Purple Finches. Other irruptive passerines, like Blue Jays, Bohemian Waxwings, and Red-breasted Nuthatches, are also on the move. "There's not enough food to support them, so they’re just spilling out of the boreal forest.” says Matt Young, ornithologist and founder of the Finch Research Network.
Many of North America’s finches live in the forests of Canada (and in northern parts and higher elevations of the United States), where they rely on a selection of conifer or other boreal trees for food—especially their fruits and seeds in the winter. However, many of these trees produce food in cycles, supplying an abundance of seeds in “mast years” and very little to no sustenance in other years. Birds dependent on these trees undergo movements in response to these cycles, staying and breeding in areas where seeds and fruits are plentiful and heading elsewhere when crops fail. In a meager year for seed stocks, birds will dip southward in search of food, and during a widespread crop failure, they venture far into the United States to find sustenance. This is one of those years.
Scientists think the trees evolved these synchronous mast-crop cycles in order to limit the food supply for seed-eating squirrels, preventing their populations from growing too large and eating all of the seeds, explains Jamie Cornelius, an assistant professor at Oregon State University who studies crossbills and is a member of the Finch Research Network. But unlike the squirrels, “birds are mobile, and can find cone crops somewhere else,” she says. In some cases, these birds have evolved strategies to cope with the occasional crop failures; crossbills molt slowly, for example, so they can be ready to fly at any moment should food run out.
These irruptions have always been a major winter event for birders and ornithologists, but they've recently become more predictable thanks to the annual Winter Finch Forecast, a report started by Ron Pittaway and now run by Tyler Hoar. The forecast uses mast-crop observations from across Canada to predict the movements of finches and other boreal species each winter. This year’s forecast predicted notable movements for a handful of species, but once fall began, more birds started moving south into the U.S. sooner and in much larger numbers than expected. Why the numbers have surpassed expectation isn't clear—the pandemic made it diffcult to collect data from the far north—but widespread crop failure is believed to be the main cause.
First came the Red-breasted Nuthatches in the summer; this “honorary finch” undergoes similar irruptive behavior, and its early movements can foretell a strong finch flight. Then, the finches began arriving, inundating northern feeders before heading south in a trickle and then a full-blown wave. Purple Finches led the way, followed by enormous flocks of Pine Siskins, including a more than 10,000 passing through Cape May’s Higbee Beach in one day. Evening Grosbeaks were next, along with Redpolls and Red Crossbills. The movements have brought mind-boggling records: a Common Redpoll visited a feeder in Albuquerque, New Mexico, while a pair of Evening Grosbeaks were found in the Florida Panhandle. Pine Siskins began migrating at night—extremely unusual for the species—and even made it to Bermuda. Meanwhile, Arctic-residing Hoary Redpolls turned up in Cleveland, Ohio.
According to Young, this year’s incredible show isn't just a product of crop failures, but also the result of a hugely succesful breeding year driven by spring food surpluses. Eastern boreal forests are experiencing their largest spruce budworm crop in decades, for example. A bane to loggers, spruce budworm larvae hatch in late spring and feast on the needles of balsam firs and spruces, which can ultimately kill the trees. The outbreak led to booms in eastern Evening Grosbeak and Purple Finch populations, who feed on the budworm. Further fueling their numbers, researchers hypothesize, was the fact that Quebec wasn't able to fully treat its forests for budworms due to COVID-19 restrictions. Meanwhile, large spruce-cone crops led to population surges of of Red and White-winged Crossbills. And Pine Siskins, which are generalists, benefitted from both the budworms and spruce-cone crops. “These populations are growing to a high level that we haven’t seen in a long time across all of these finch species,” Young says.
The abundance of summertime food followed by the widespread crop failure unexpectedly lined up for finches across species and across North America, says Hoar of the Finch Forecast. There were few food sources for the budworm-loving birds once the budworm season ended, and the scarcity of food wasn’t just limited to forests in northern Canada. “The food sources that would have held back most of those finches in southern Canada and northern border states were mostly quite poor,” he says. “So the birds kept moving further south in search of food.”
The West has coincidentally gotten a taste of the finch fun for reasons unrelated to the boreal forests. Southern California-breeding Lawrence’s Goldfinches have poured into Arizona as part of their own food-dependant cyclical movements, and Cassin’s Finches have shown up farther east than usual, perhaps due to their own irruptive cycles aligning with this past summer’s wildfires, says Young.
The Evening Grosbeak showing is perhaps most notable. The striking finches have become increasingly scarce in the eastern U.S., so such a big irruption has been thrilling for birders and experts. While this year's irruption isn’t record-setting, future irruptions could be, say Young and Hoar. Both point to a budworm outbreak in the 1970s that brought Evening Grosbeaks to feeders across the country in droves. As the current budworm outbreak intensifies in the coming years, it may continue to drive Evening Grosbeaks and even bigger irruptions that could rival those numbers from the 1970s.
Luckily for birders stuck at home during this pandemic-stricken 2020, all of these finches are hungry and showing up anywhere there's a meal. “Winter finches are saying ‘hey, we need food, we need food,’” Hoar says. So if you can do so safely, get outside and try to find some of these winter visitors at your local park. And if you have feeders, be sure to keep them stocked, maybe buy some backup seed, and enjoy the show.