You hear them long before you see them: a raspy, gurgling call builds on the horizon. Sandhill cranes. Hundreds, even thousands, flying in endless branching formations or circling on a rising thermal. Over a period of less than two weeks in early May, an estimated 250,000 will follow Yukon’s Tintina Trench, traveling from wintering sites in the southern U.S. toward breeding sites in western Alaska and Siberia.

 Sandhill cranes (Grus canadensis) migrate in large branching formations calling steadily as they soar on uplifting warm air. (Credit: Hilary Cooke/WCS Canada)

Most birds that breed in our Boreal and Arctic biomes migrate to and from wintering ranges in North, Central and South America. They are among the estimated six billion North American birds that migrate annually.

Spring migration anywhere is exciting. But there is something different, almost exhilarating, about spring migration in the North. Through the long winter months, I almost forget there is a time of year that is not cold and dark, and blanketed by a quiet that is interrupted only by the call of ravens. And then, after much anticipation, spring is here. First, the snow buntings and other Arctic breeders. Next, the juncos and sparrows that winter in the milder climates of southern Canada and other less frozen places. Then, finally, the long-distance warblers and flycatchers making the trek from South America to boreal breeding grounds. Every day brings new arrivals.

Arriving in southern Yukon in late April, Golden-crowned sparrows (Zonotrichia atricapilla) migrate from wintering areas along the Pacific coast of the U.S. to breeding sites in Yukon’s subalpine. After a much longer journey from Brazil, Yukon’s blackpoll warblers (Setophaga striata) arrive 3 weeks later and settle on breeding territories in boreal wetlands. (Credit: top- John Meikle; bottom - Jukka Jantunen)

Migration allows birds to take advantage of the seasonality of resources in different places and habitats. However, these long journeys are risky and require significant energy. Sites for stopping to rest and refuel along the way are critical for birds to complete their migrations and have a successful breeding season.

Many of our Arctic and Boreal migratory birds are experiencing population declines linked to climate change, habitat loss, building collisions, cat predation, and other threats. I sometimes get overwhelmed thinking about the threats facing migratory birds. But, I know that protecting stopover sites in Yukon’s intact boreal landscapes is critical to bird survival, and one piece of the complex puzzle of conserving our migratory birds.

During migration, birds often track dominant features of a land or seascape - coastlines, river valleys, peninsulas and mountain ranges. For example, every spring, cranes, ducks, geese, raptors, shorebirds and songbirds migrate along Yukon’s Tintina Trench. Formed along a continental fault line, the Trench is a long valley ranging in width from two to 12 km, bounded by mountains and rolling plateaux and running 960 km northwest from southeast Yukon. It’s been frequently described as an important migratory flyway, yet there have been few studies of the region and no comprehensive studies of locations of critical stopover sites and habitats for migrating birds along its length.

 Yukon’s Tintina Trench is a geophysical feature that is thought to guide migratory birds as they travel from flyways to the west and east of the Rocky Mountains towards breeding sites in northern Yukon, Alaska, and Siberia. (Credit: top - Base map, USGS; bottom - Fred Beaudry/WCS Canada)

This is a remote mountainous area with few roads, and fewer people. But southeast Yukon has been experiencing a slow creep of resource development for decades and there is currently no formal process for protecting sites and habitats of high ecological value. That’s why we need to locate sites that are priorities for conservation, and seek both short-term and long-term protective measures.

Right now, our work here is focused on identifying and protecting the most important spring stopover sites. Some sites provide a small but critical place to rest in an otherwise inhospitable landscape. Others provide abundant food and shelter, allowing for longer stopovers and an opportunity to rebuild muscle and fat. Think of these as ranging from a roadside rest stop to a full-service hotel and restaurant.

In early spring when most Yukon lakes and rivers are still frozen, small ice-free openings provide the only open water for migrating swans, geese, ducks, loons, grebes and other waterbirds. Through multiple surveys of numerous lakes across several years, our research will provide the scientific evidence necessary to advocate for protection of the highest-value lakes.

 Even in early May, much of southeast Yukon’s mountainous boreal landscape is covered by snow and ice (top). Small ice-free patches on lakes and rivers provide the only open water for migrating ducks, geese, swans, loons, and grebes (bottom). (Credit: Hilary Cooke/WCS Canada)

This year we will also start to tease apart the incredible story of sandhill crane migration. Tucked in a pinch point of the Trench is the remote community of Faro. It is THE place to witness the migration. In 2017 we spent days listening and scouring the skies for the cranes, not realizing that when they came it would be like nothing we had ever imagined. We were awestruck -- and mesmerized -- as we counted 45,000 cranes passing overhead in less than 48 hours. Take a moment to experience it yourself (https://youtu.be/eI_0NIOE8z8).

Cranes are known to roost and feed together in the tens of thousands. But despite an estimated 250,000 migrating through over a period of less than two weeks, no sites have been found that are used by large congregations in this region. (A previous study located about 30 sites where 15 cranes wearing satellite tracking devices stopped to rest, but never together.) We will continue the search using helicopters and by deploying remote wildlife cameras and acoustic recording devices across this vast, wild area in our ongoing effort to pinpoint important resting sites.

Barrow’s Goldeneye (Bucephala islandica) and Surf Scoters (Melanitta perspicillata) rely on open water during spring migration between their wintering areas off the Pacific coast and their breeding lakes throughout the boreal. (Credit: Hilary Cooke/WCS Canada)

The past year has been a roller coaster for my hopes for the future of our migratory birds. While new areas have been protected in Canada, protections have been rolled back in the United States.

Spring, and days spent witnessing the unfolding spectacle of bird migration, lift my spirits and my hope, and gives me a positive foothold to start the coming year. I think of this work – of protecting stopover sites for migrating birds needing a place to rest and refuel – as ensuring they have footholds too.

So, even as another foot of snow fell over recent weeks, we’re finally teetering on the edge of spring and it’s just a short two weeks until our field work begins. I can’t wait.