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Dave Ewert Talks about Migratory Birds at Cranbrook

Dr. Dave Ewert, a senior scientist for The Nature Conservancy, recently spoke as part of the six-part lecture series "What's So Great About the Great Lakes?" at the Cranbrook Institute of Science. He discussed the importance of protecting habitat for the millions of migratory birds that fly through the Great Lakes region every year.

You can watch his full lecture here or catch the top takeaways below.

The Nature Conservancy:

What makes a migratory bird different from other birds?

Dr. Dave Ewert:

Migratory birds have two “homes.” They breed in their northern home during the summer months, usually from April until August; then they fly to their southern home for the rest of the year. Migratory birds breed throughout the United States and Canada, and fly south to Mexico, Central America, and the Caribbean Islands for the winter. In order to survive and reproduce successfully, migratory birds need access to both of their “homes,” and stopover sites between breeding and wintering areas, which is why they are more difficult to protect.

The Nature Conservancy:

Do we know that birds migrate?

Dr. Dave Ewert:

Scientists have been studying bird migrations for decades. Typically, a migratory bird is caught and a small aluminum band is placed around its ankle. This band has a number and color unique to that bird, so when it is caught again, we can mark its location. Some scientists have been using geolocator technology to track the birds as they migrate, so the path can be traced during flight. Both of these methods allow us to evaluate locations of wintering and breeding areas and, with geolocators, to identify migratory routes and the amount of time it takes for a bird to travel between breeding and wintering areas. Birds also have the impressive ability to return to the exact same locations year after year.

The Nature Conservancy:

How long does it take a bird to migrate?

Dr. Dave Ewert:

It can vary depending on the weather and how often the bird needs to stop and rest. I study Kirtland’s warblers in both their Michigan and Bahamian habitats, and we once saw a particular warbler in the Bahamas one day and again in Michigan thirteen days later. It’s quite amazing that a one ounce bird can complete such a long and physically demanding journey.

The Nature Conservancy:

Why are migratory birds vulnerable?

Dr. Dave Ewert:

Migration is very stressful for birds, and in fact, mortality is fifteen times greater during migrations than other times of the year. Migratory birds encounter a lot of hazards on their flights. Some are natural, such as predators and weather, but some are human-created. Cities are often built near large bodies of water where birds tend to travel and present hazards to birds during the journey, such as collisions with buildings. Habitat loss is one of the greatest threats to migratory birds. The birds stop multiple times during their journey, and they need what we call stopover sites in order to rest and refuel. If the birds’ ideal habitat has been destroyed or fragmented, or divided into smaller areas, the birds are less likely to survive the migration. It has been estimated that 100,000,000 birds and 300 different species use stopover sites in the Great Lakes region, so it’s important that we conserve lands where the birds can rest.

The Nature Conservancy:

How does a bird choose where to stop?

Dr. Dave Ewert:

I like to place potential resting spots into three different categories. The first is what I call a “fire escape,” which is only used by the birds when there is nowhere else to land. A good example is a boat in the middle of a lake, or a tree in the middle of an urban park. A “convenience store” is the next type. It is of better quality than the “fire escape” types and is used occasionally. The ideal stopover site for a migratory bird is what I call the “full-service hotel.” This site has a variety of vegetation for food and shelter, as well as a body of water nearby. It is also large and unfragmented. A good stopover site can house many species of birds because it has many layers of vegetation, from shrubs on the ground to trees with a high canopy, and a mix of deciduous and coniferous trees.

The Nature Conservancy:

How do you help birds find good stopover sites?

Dr. Dave Ewert:

Our main goal for migratory bird stopover sites is to provide high quality habitat for the birds to use, based on the descriptions I just mentioned. The locations of these sites through migratory pathways are just as important. We have been mapping where migratory birds tend to stop, and listing priority areas based on use. These maps, as well as other data and useful information on migratory birds, are being integrated into a web portal so that The Nature Conservancy, our partners, and local governments can manage the land in a way that maintains and improves stopover sites. The research we have done and will continue to do help fill information gaps and will hopefully make it easier for people to create stopover sites.

The Nature Conservancy:

What do you think is an important way to improve migratory bird stopover sites?

Dr. Dave Ewert:

Based on my experience with previous projects, providing economic incentives is a great was to encourage the creation of stopover sites. It’s been estimated that in Michigan alone, 11 percent of tourists watch birds, so that alone provides a large flow of income for the state. Economic incentives tend to be most important for businesses. One company was spending $10,000 yearly on a lawn-mowing contract. We suggested that they let the vegetation grow naturally, and it has saved the company thousands of dollars while providing some great shelter for the birds. Little changes like that can make a big difference when birds need a place to land.

The Nature Conservancy:

What can I do to help migratory birds?

Dr. Dave Ewert:

The easiest place to start is in your own backyard. We have put together some guidelines to help people manage habitat on their property. I’ve let my own backyard grow naturally and I’ve even added some serviceberry, blueberry, and juneberry bushes, as well as dogwood, tamarack, black spruce, and hemlock. It’s really wonderful when I look out my window and see a hermit thrushes and white-throated sparrows hopping around. For you avid birders, I even saw a small flock of bohemian waxwings one winter day.


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