Keeping Track of These Boreal Nomads Is Notoriously Difficult

The irregular irruptions of winter finches inspire both delight and bewilderment among migration scientists.

March 3, 2021

Jeff Wells and Chad Witko, National Audubon Society

Boldly yet delicately colored in swaths of yellow, salmon, frost white, or raspberry, the beauty of winter finches is a welcomed sight to what is often a pallid landscape across the northern tier of the United States. But our love affair with these birds, which include Evening Grosbeaks, Pine Grosbeaks, Purple Finches, Common Redpolls, Hoary Redpolls, Red Crossbills, White-winged Crossbills, and Pine Siskins, goes beyond their refined color palette. We are transfixed by their annual movements, particularly their incredible irruptions outside of their expected ranges, in search of food. These nomadic travelers border on the mythical, as if our winter finches were driven south on the divine north winds of Boreas or Negafook themselves. There is no question about it, winter finches are both beautiful and wild. It is their very essence.

With such endearment and reverence, it should come as no surprise that a great deal has been written about our winter finches, particularly how to find them. No work is more acclaimed in this regard than the famed Winter Finch Forecast— a prophecy of if, when, and where large numbers of these birds will arrive each winter. However, despite scientists’ rudimentary ability to predict large, continent-level movements of winter finches based on the presence and abundance of cones, catkins, seeds, and berries, we still know little about the detailed movements of individuals or even distinct populations for many species. Compared to other groups of similarly sized songbirds like warblers or thrushes, there are relatively few tracking data on winter finches. These data would be extremely helpful in better understanding the nature of their irruptions, including where individuals and populations of finches go year after year if they even move at all. This absence of tracking data is not due to a lack of interest from researchers, but rather the direct result of the movements of winter finches themselves. To gain critical insight into their irruptions, researchers will need to overcome the many challenges studying winter finches present, including the very thing they wish to learn more about, their extraordinary movements.

Fortunately, the tides of understanding winter finch migrations and irruptions are changing, thanks, in part, to organizations such as the Finch Research Network, which with select partners is helping to fund tracking studies on Evening Grosbeaks and Red Crossbills. By using advanced and developing tracking technologies, researchers hope to fill in these critical data gaps to better understand our winter finches' full annual cycles, something scientists hope will provide essential insight into conserving their habitats, including the Boreal Forest.

*An Evening Grosbeak, Credit: Jeff Nadler*

The most significant overarching hurdle in tracking winter finches is that many traditional tracking technologies small enough to be deployed on this group of birds, such as geolocators, require the researcher to retrieve the data loggers at a future date to access the data. Due to winter finches’ irruptive and nomadic nature, this can be nearly impossible. Comparatively, this technological constraint presents itself only as a minor challenge when studying other songbirds like warblers, which like many migratory species, exhibit extreme site fidelity. That is, they return to the same breeding territory each year, allowing researchers to trap the same individual and remove the device.

But unlike studying songbirds breeding in the eastern forests or our shrublands, gaining access to finch breeding grounds in the Boreal Forest can be extremely challenging. The Boreal Forest is considered one of the forest ecosystems on the planet with the least amount of large-scale industrial scale disturbance. That makes it a rich breeding area for vast numbers of birds— an estimated one to three billion birds nest there, including two-thirds of North America’s finches— but much of its 1.5 billion acres is without roads, making it very difficult to access. Even if our winter finches exhibit side fidelity to the same breeding territory year after year in some areas, to deploy transmitters on distinct populations of finches across the Boreal Forest would be a logistical undertaking that many research projects are unwilling or even capable of taking on.

Further complicating the picture of trying to deploy traditional transmitters on the breeding grounds is the fact that some finch species, such as Red Crossbills, do not always breed in the same place year to year. Instead, they exhibit opportunistic breeding in response to a changing food supply. As cone-producing trees such as pines, firs, and spruces offer bumper crops based on local conditions and cyclical intervals, Red Crossbills may nest two or more times in a single year in one place when conditions are good and then move vast distances between breeding attempts in search of better circumstances. While these generalized movements and breeding efforts can be predicated on regional scales due to the seasonal patterns of seed availability, finding individually breeding birds again to retrieve tracking devices such as geolocators would be nearly impossible. It is the proverbial needle in a continent-sized haystack.

While gaining access to the breeding grounds to study breeding Boreal finches is challenging, it is equally as challenging to work with them on their wintering grounds or in the areas where they regularly or even rarely irrupt. During the winter, year to year, winter finch movements are unpredictable. While some species such as Evening Grosbeaks may irrupt and be found in the same local several years in a row, there is no guarantee that individual birds outfitted with a tracking device would even migrate or irrupt, let alone to the same place. Further, some species of winter finches can sometimes go several years without making any significant movements. As a result, there is a distinct possibility that a small device with a limited battery would not detect any movements at all during the time it is deployed, let alone even be retrieved. Therein lies the rub— the very thing researchers are looking to learn about—seasonal finch movement—prohibits its very study.

Thankfully, we are entering into a new golden age of bird tracking, where researchers interested in studying winter finch movements are increasingly able to rely on advanced technology. For example, new, solar-powered tags are designed to deliver data to radio networks, including Motus, for the entire life of the animal. A collaboration in western Pennsylvania, including efforts from the Pennsylvania Natural Heritage Program and the Finch Research Network, is currently using this technology to better understand the breeding origins of Evening Grosbeaks, to see if they exhibit true site fidelity and how far-and-wide they range during winter. Eventually even space-based technology like the ICARUS Initiative on the International Space Station will open greater opportunities for tracking small birds.

These developments in tracking technology are important milestones in bird conservation. Unfortunately, Evening Grosbeaks are one Boreal finch species that has seen a massive decline in overall abundance during the last 30 years, resulting in Canada listing the bird as a species of special concern. Evening Grosbeaks, like all the other winter finches, are listed as vulnerable to climate change according to Audubon's own climate research. Conservationists have less information on the population trends and status of other Boreal breeding finch species because of the remoteness and inaccessibility of the bulk of their breeding ranges. New migration tracking research will help to understand where to target more breeding ground research but may also help to understand whether trend estimates derived from wintering ground surveys pertain to specific regional Boreal breeding populations.

Migration tracking research will also be critical to defining the Boreal landscapes that are most important for maintaining healthy populations of Boreal finches. Across the Boreal, Indigenous Nations are proposing new Indigenous Protected and Conserved Areas, and these areas may overlap with lands that are important for breeding finches. Not only would these new protected areas help sustain finches into the future, but they will also help the Government of Canada meet its global Convention on Biological Diversity goal of protecting 30 percent of its lands and waters by 2030 (and 25 percent by 2025).

The fact that Boreal finch populations can grow to large sizes and irruptive events can occur over continental scales is because of the vast size and intactness of the Boreal Forest biome of North America. The Boreal Forest biome is estimated to hold within its borders more than 500 billion trees, largely dominated by the spruces, firs, and pines that produce the seed-bearing cones upon which most Boreal finches feed. When large numbers of these coniferous trees in the same region all have particularly good cone production at the same time, this provides a food bonanza that allows Boreal finches to raise more young.

While traditionally thought of as winter finches, there is a good chance many of us will be experiencing these amazing birds throughout portions of spring. According to Matt Young, President and Founder of the Finch Research Network, the return flight of this winter’s massive superflight is about to begin, and everyone in the northern tier states should be on the lookout. “It'll start with Pine Grosbeaks and Redpolls in March,” says Young. "However, it won’t end there, as Pine Siskins, Purple Finches and Evening Grosbeaks all made it to Florida and will still be coming north into May!”

The Migratory Bird Initiative hopes to acquire winter finch tracking data as they become available to include in the upcoming Migratory Bird Conservation Platform and ongoing conservation assessments, including those for the Boreal Forest. If you are a researcher studying the movements of our Boreal-breeding winter finches and would like to contribute tracking data to Audubon’s Migratory Bird Initiative, please contact us at migratorybirds@audubon.org. Additionally, the Finch Research Network is now fundraising to support students and continue studies on focus species, including Red Crossbill, Evening Grosbeak, and the trio of rosy-finches, mountaintop specialists at risk due to climate change. These studies will involve the use of both transmitters and autonomous recording units to track these mysterious finches.

If you would like to learn more about Audubon’s efforts to protect the Boreal forest, please visit: https://www.audubon.org/conservation/boreal-forests.

For more information on the Finch Research Network, please visit https://finchnetwork.org/ or contact Matt Young at info@finchnetwork.org.

Chad Witko is an outreach biologist for the Migratory Bird Initiative, and Jeff Wells is Audubon's vice president of boreal conservation.