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Every summer, thousands of birds in Minnesota begin migrating south in August. St. Olaf faculty members Sean Peterson and Lynn Schofield talk about the importance of the birds’ migration cycle to Minnesota’s environment: 

Why is it important to have a variety of bird species? How do their migration cycle or routes reflect the health of our environment?

Schofield: Species diversity is directly related to ecosystem function and stability. A healthy ecosystem is an interconnected ecosystem with complex and dynamic relationships between a myriad of species. Each species is dependent on the existence and presence of others.

Peterson: For example, the Willow Flycatcher is a bird that relies on willow shrubs to provide nest sites and to support the insects they feed on. If there are no willows, there are no willow flycatchers. Willows require wetland habitats, the most favorable of which are beaver ponds — and in some regions, the only suitable wetlands are those created by beavers. So, if beavers are lost in an area, it causes a huge cascading effect on biodiversity that also wipes out willows and the Willow Flycatcher. These sorts of dependent relationships are present in every ecosystem and every species, including humans.

Schofield: Birds are one of the best ‘model organisms’ when it comes to studying ecological processes because they are easily observed in the wild. They are active, brightly colored, diverse, easily identified, and they announce their presence through song. That’s why bird watching is such a popular hobby. The presence of a diversity of bird species, each specialized to a unique lifestyle speaks to the complexity of the systems they are part of. Migratory birds are an especially interesting group to study when it comes to topics of ecosystem health, because a single species can be connected to habitats spread across continents. While individually very small, migratory birds operate ecologically on a trans-hemispheric scale. For migratory species to flourish, they need productive habitat at their breeding grounds, their wintering grounds, and along their migratory path.

Peterson: There are 27 species of wood warblers — a family of small, colorful insectivores — regularly found in Minnesota. All of which are long-distance migrants. While warblers are physically very similar, they have highly specialized lifestyles and niches. About half of our warbler species’ populations have declined over the last 50 years. Despite tremendous conservation efforts invested in preserving breeding habitat, the declines continue. Recent studies have identified strong links between population declines here in Minnesota and the health of habitats in Central and South America, where warblers spend the winter. Bird populations are a reflection of ecosystem health, not only in Minnesota, but in every other place those birds live during their annual cycle.

Can our natural environment (wetlands, prairie, forest, etc.) affect the bird migration, or vice versa? If so, how? 

Schofield: As with all organisms, each species of migratory bird has its unique association with its environment. These habitat associations can shift throughout the year, changing between breeding, migration, and winter. During migration, birds need a habitat where they can forage quickly and safely to build up energy to continue on their travels. What that migration habitat looks like depends on the preferred food sources and foraging habits of the bird as well as their safest habitat.

Peterson: Most birds also migrate along very specific corridors, so the environment along those narrow routes can have a tremendous impact on the success of migratory birds. One of the biggest routes is the Mississippi Flyway, which funnels birds from Louisiana up through Minnesota and into Canada. Billions of migratory birds use this flyway as a connection between their breeding grounds and their wintering grounds. Conserving habitat along this flyway is instrumental to providing safe passage for hundreds of species every spring and fall.

What specific bird species depend on each of these ecosystems in Minnesota? 

Schofield: There are some iconic bird-habitat associations in Minnesota. Our state bird, the Common Loon, is deeply connected to the Minnesotan psyche because it is so closely associated with our beloved lakes. Loons are entirely dependent on open water, and they cannot freely move on land. They will spend winters in the ocean, but they move inland to breed and need a path of lakes to stop at during each step of their journey to their breeding grounds.

Peterson: Minnesota forests are an incredibly important resource for many species, but we’ll point to the Golden-winged Warbler as an important example. This gorgeous little bird specializes in complex forest structures found in abundance in the northern half of the state. Over 50% of the global population of Golden-winged Warblers lives right here in Minnesota. In addition, our population of these birds is one of the only ones in the country that isn’t precipitously declining, suggesting that not only are Minnesotans providing the exact habitat they need to successfully raise families, but our partners in Colombia and Venezuela are also providing the conditions that this population needs in South America to survive the winter.

On the flip side of the coin, prairie species are among the most vulnerable. Only 1% of Minnesota’s native prairie remains. Even now, prairies are disappearing at an alarming rate of 1-2 million acres per year nationally. This has led to half of all grassland birds in the U.S. lost in the last 50 years. In the fragments of prairie that remain, specialists like the Eastern Meadowlark, Grasshopper Sparrow, and Bobolink are still hanging on, but their future here is tenuous. 

Schofield: Prairie restoration work has become a conservation priority in the state, but the conservation community will need to work hard to provide a network of connected habitats across the full extent of these birds’ migratory routes to allow these species to recover.

What are the modern day challenges birds encounter when it comes to safely migrating and their environmental habitat?

Schofield: For migratory birds of all types, migration is the most dangerous period of their lives. The chance of surviving each day is reduced by about fifteen times while a bird is moving between breeding and wintering habitats. It takes enormous amounts of energy to travel such long distances, and the dangers at each stop are new and unfamiliar. Humans are making migration even harder, too. Places once safe to rest and refuel are becoming developed and populated. What were once oases have become new sources of danger.

Cats, windows, and cars are the three most common direct causes of bird mortality. The threat of windows is especially pronounced for migrating songbirds, which typically fly at night, because they become disoriented by brightly lit buildings. Due to climate change, even the weather is working against migrating birds — to achieve some of the fantastic feats of endurance migrating birds are known for, like crossing the Gulf of Mexico in a single night, birds rely on favorable winds and weather. The winds birds need are less reliable than they once were. 

Even for those birds that make the trip successfully, many are now arriving too late to their breeding grounds as spring is coming sooner, and their food sources are no longer at their peak when breeding birds most need them. Plants are leafing out earlier, which causes insects to emerge earlier, but migratory birds are lagging behind. This makes nesting a much more difficult proposition each year as food supplies shift earlier and earlier relative to the timing of laying eggs and raising chicks.

How does your work at St. Olaf support educating students and the community in preserving the birds’ habitats during migration season?

Peterson: For the past three years, we have run a bird banding station in the natural lands at St. Olaf with students participating in the Collaborative Undergraduate and Research Inquiry program. This research station is a part of a network of over 1,000 similar stations that monitor bird populations across North America. Student researchers have pursued projects that assess how much bird morphology has changed due to climate change and how juvenile birds interact with one another. Our research helps us better understand trends in migratory birds and what habitats they use at different points in their lives. Bird banding allows individual birds to be identified wherever they are found, so we would know any time a bird banded at St. Olaf was found elsewhere in its migratory pathway.

As St. Olaf is so focused on global citizenship and international collaboration, we try to integrate those views into our coursework and research wherever possible. Understanding migratory bird populations and conserving habitat is not limited to what we do here in Minnesota, but requires extensive international cooperation. The data students collect here feeds into international databases that really help us understand the importance of preserving habitats not only at home, but also across the world.

Schofield: We would also like to highlight some of the work of our students. We have the pleasure of being the advisors for the St. Olaf Bird Alliance, which has recently become the first official student chapter of the Audubon Society in the state of Minnesota. To be a student chapter with Audubon, group members need to participate in outreach activities and contribute to conservation or research. The St. Olaf bird alliance has helped to coordinate bird walks, tabling to raise awareness about conservation campus-wide, and is currently tackling potential research and conservation projects on campus.

Sean Peterson is a visiting assistant professor of biology at St. Olaf. His academic interests are in spatial ecology, population modeling, and using novel technologies and methods to advance our understanding of animals. Prior to joining the college, he received his bachelor’s from Macalester College, master’s from the University of Minnesota, and studied the ecology of Black Rails in the Sierra Nevada during his tenure at the Beissinger Lab within the University of California Berkeley. His graduate work focused on modeling habitat occupancy and productivity, post-fledging parental care, animal movements, and remotely sensed data. 

Lynn Schofield is a visiting instructor of biology at St. Olaf and a research biologist at The Institute for Bird Populations. Her academic interests include bird migration and movement, spatial ecology, fire ecology, meadow conservation, and how habitat and environmental changes impact bird populations. Before St. Olaf, she received her bachelor’s from University of Minnesota, Twin Cities and master’s from Eastern Illinois University. Her graduate research focused on avian habitat use and behavior during migration. Before coming to St. Olaf, Schofield also worked for The U.S. Forest Service, San Francisco State University, and The National Park Service among others.