Warmer weather finds many birds again on the move, but this time heading north instead of south. The phenomenon of summer migration brings colorful neo-tropical species back to breed in northern habitats. So where do birds migrate in the summer months?
Read on to learn about major summer flyways, destinations for migrating birds based on their starting region, and how you can support migrating birds on their northerly spring and summer journeys.
Why Birds Migrate for Summer
What prompts the mass exodus of birds from their tropical wintering grounds back up to northern latitudes each summer? Several key factors drive summer migratory patterns:
Taking Advantage of Long Days
Increased daylight in the far north during the summer enables birds to find ample food and successfully raise multiple clutches. The non-stop light facilitates nearly continuous foraging.
Finding Plentiful Food
The bloom of insects, plants, and other prey in northern regions supplies birds with abundant nutrition for breeding and rearing offspring.
Accessing Nesting Sites
Some species rely on specific northern nesting habitats like wetlands, tundra, and boreal forests, which are unavailable further south.
Escaping Competition
Lessened competition for food and nest sites in the far north enables migratory birds to thrive in breeding grounds untouched by overwintering species.
So in summary, the north’s long summer days, plentiful food sources, ideal nesting spots, and reduced competition all draw migratory birds up from southern latitudes each year to mate and rear young.
Major Summer Migration Flyways
Just as with fall migration, most species follow the same established superhighways north each summer:
Atlantic Flyway
The Atlantic flyway stretches up coastal eastern North America.
Starting & Ending Points
- Starting points: Florida, Caribbean, Central & South America
- Ending points: Northeastern Canada, New England, Atlantic Canada
Key Stopover Spots
- Coastal Virginia
- Delaware Bay
- New Jersey Coast
- Long Island, NY
Birds here include American redstarts, purple martins, and bobolinks.
Mississippi Flyway
The Mississippi flyway extends up the Mississippi River valley through the heart of the continent.
Starting & Ending Points
- Starting points: Gulf Coast, Central America
- Ending points: Central Canada, Midwest U.S.
Key Stopover Spots
- Texas Coastal Prairies
- Lower Mississippi Valley
- Missouri River
- Platte River, Nebraska
Some birds using this route are chimney swifts, barn swallows, and yellow-headed blackbirds.
Central Flyway
The Central flyway crosses the Great Plains up through the middle of North America.
Starting & Ending Points
- Starting points: Mexico, Southwestern U.S.
- Ending points: Prairie Canada, Rocky Mountains
Key Stopover Spots
- Cimarron Grasslands, Kansas
- Rainwater Basin, Nebraska
- Grasslands National Park, Saskatchewan
Birds migrating here include lark buntings, long-billed curlews, marbled godwits, and upland sandpipers.
Pacific Flyway
The Pacific flyway extends up western North America along the Pacific Coast.
Starting & Ending Points
- Starting points: Mexico, U.S. Southwest
- Ending points: Pacific Northwest, Western Canada, Alaska
Key Stopover Spots
- Klamath Basin, Oregon
- Puget Sound, Washington
- Fraser River Delta, British Columbia
Some Pacific flyway migrants are western tanagers, black-headed grosbeaks, rufous hummingbirds, and northern pintails.
Next, we’ll break down summer migration destinations in more detail by region and species.
Summer Destinations by Region
The distances and endpoints for summer migration depend on the species and their starting point further south:
Northeastern Birds
Birds overwintering in Central and northern South America, like barn swallows, chimney swifts, wood thrushes, and scarlet tanagers, migrate long distances up through the eastern flyways to breed in the northeastern United States and Canada.
Midwestern Birds
Species like cliff swallows, dickcissels, bobolinks, and orchard orioles winter in the southern U.S, Mexico, and Caribbean before taking shorter migrations up through the Mississippi and Central flyways to nest in the Midwest and Prairie Provinces of Canada.
Western Birds
Western species like calliope hummingbirds, Bullock’s orioles, Lazuli buntings, and willow flycatchers move relatively short distances north through the Pacific flyway to breed across the western United States and Canada.
Southern Birds
Some southern residents, like Carolina wrens, eastern bluebirds, northern cardinals, and tufted titmice, may migrate short distances north or to higher elevations like the Appalachians for summer breeding. Others, like Florida scrub jays, stay put year-round.
So the distances covered vary significantly based on latitude. Next, we’ll look at how birds time their migrations.
How Birds Time Their Migration
The triggers prompting birds to start summer migration require extremely precise timing. Being too early or late can jeopardize breeding.
Birds rely on the following cues to get their timing right:
Responding to Changing Day Length
Increasing daylight in spring triggers hormonal changes that spur migration and breeding instincts. The consistent variation helps birds determine seasonal timing.
Sensing Weather Patterns
Warmer temperatures and favorable winds help signal birds to depart their winter grounds. Some may wait for passing storms to clear before migrating.
Following Innate Rhythms
Migratory birds possess inner annual clocks and instincts that drive them to migrate and breed during optimal seasons based on their species. This intrinsic programming fine-tunes their timing.
So seasonal cues like sunlight, warmth, and innate rhythms spur summer migrations to keep birds on schedule for breeding upon arrival.
Navigation Methods for Summer Migration
Heading to unfamiliar northern grounds they’ve never visited presents navigational challenges for young migratory birds. How do they find the way? Key strategies include:
Orienting With Earth’s Magnetic Field
Birds likely sense the earth’s magnetic fields via deposits of magnetite in their beaks and brains to determine direction. This serves as a natural compass.
Using the Sun and Stars
Celestial cues from the sun during the day and stars at night provide orientation. On cloudy days, patterns of polarized light can still be detected.
Following Coastlines and Mountain Ranges
Major geographic features like coasts and mountain ranges act as visual guides for migrating landbirds and seabirds.
Recognizing Landmarks
Familiar manmade and natural landmarks are used to navigate along frequently traveled migratory flyways and to specific breeding sites.
So from celestial guidance to inbuilt compasses, young migratory birds follow proven navigational strategies to locate northern destinations they’ve never before encountered.
Challenges Faced During Summer Migration
While summer migration brings the reward of ideal breeding conditions, journeying to those northern habitats presents some daunting obstacles for birds.
Finding Food at Stopovers
Migrants require abundant food at stopovers along their route to refuel. Certain sites along the Mississippi and Central
Flyways provide essential foraging spots. Loss of wetland feeding grounds can endanger migrating birds.
Battling Exhaustion
The physical demands of long migrations place strain on birds. Some species fly thousands of miles nonstop over several days, pushing their endurance limits. Refueling and resting along the way is crucial.
Coping With Weather Extremes
From thunderstorms to harsh winds and cold snaps, migrating birds are vulnerable to variable spring weather. Storms can blow migrants dangerously off course.
Avoiding Predators
Birds stopping over in unfamiliar areas face heightened threats from predators like hawks, cats, snakes, and raccoons. Vigilance is vital for migrants.
Navigating Human-Made Obstacles
Finally, human structures pose risks, from glass windows and power lines to communications towers. Light pollution can also disrupt navigation for night migrants.
Despite these challenges, migration ensures species access optimal breeding grounds in northern latitudes each summer.
How to Help Migrating Birds in Summer
Here are some tips for supporting migratory birds passing through your area on summer migrations:
Provide Food and Water
Supply seed and nectar feeders, suet, and fresh water for drinking and bathing to help refuel migrants.
Avoid Pesticide Use
Reduce or eliminate pesticide usage so birds can access nutritious native insects at stopovers.
Make Windows Safer
Minimize collisions by marking glass or installing screens. Close blinds and turn off lights at night.
Keep Cats Indoors
With increased birds in your yard, keep cats inside to reduce predatory threats.
Support Conservation Efforts
Back local and national efforts to preserve migratory habitats like wetlands and native grasslands vulnerable to development.
Following these tips will help create an oasis for migratory birds heading your way each summer.
Additional Challenges Faced During Summer Migration
Migrating birds face numerous threats on their northbound spring journeys, in addition to those already covered:
Loss of Stopover Habitat
Wetlands, forests, and grasslands that provide crucial stopover habitat continue to be lost to development, draining, and pollution. Lack of places to rest and refuel heightens migratory perils.
Severe Weather Events
Climate change has increased storms, floods, fires, droughts, and other extremes en route. Events like Midwest derechos can kill thousands of migrating birds in an instant.
Colliding with Structures
Urbanization exacerbates collision risks. One billion birds a year die from building and tower strikes in the U.S. Making structures and lighting bird-friendly is an urgent need.
Pesticide Exposure
Pesticides like neonicotinoids can sicken and kill birds at stopovers. These chemicals also decrease insect prey. Banning harmful pesticides would aid migrants.
Invasive Species
Invasive plants and animals at stopovers compete with native species that birds rely on. They degrade the habitability of sites like wetlands. Limiting introductions protects ecosystems.
Drawing the Map in Reverse
Young birds migrating north for the first time perform the incredible feat of drawing their mental navigation map in reverse of their initial southbound route. This demonstrates birds’ vast innate migratory knowledge.
Additional Ways to Help Migrating Birds
Some further actions you can take to protect birds during spring migration include:
Volunteer Citizen Science
Join community science efforts like the Cornell Lab of Ornithology’s eBird to report bird migrations. This data aids in research and conservation.
Educate Others
Spread the word about migratory perils and how people can help. Share information via social media or hang flyers at community spaces to expand engagement.
Keep Trees Healthy
Ensure trees have space, soil, and water to grow. Healthy native trees supply insects and provide good stopover spots near homes.
Reduce Lawn Chemicals
Avoid using insecticides, herbicides, and fungicides. They limit prey for migrants and pollute the water sources birds rely on.
Pack Out Trash
Pack out any garbage rather than leaving it behind, which can entrap or poison birds exploring stopovers. Lead by example while enjoying the outdoors.
Contribute to Conservation Groups
Donate or volunteer for groups like the Audubon Society, American Bird Conservancy, Cornell Lab of Ornithology, and local land trusts to pitch in.
Every action to counter habitat loss, climate change, pollution, collisions, and other threats assists migrating birds on their extraordinary seasonal journeys.
The Magnetic Map Sense of Migratory Birds
In addition to using the sun and stars for orientation, migratory birds possess an incredible “magnetic map” sense. Embedded magnetite crystals in their beaks and brains enable them to literally see the Earth’s magnetic fields as visual patterns and shapes that provide detailed geographic information.
Experiments have shown that interfering with birds’ magnetic sensory organs impairs their ability to navigate accurately during migration. This magnetic map helps guide birds thousands of miles to precise locations across hemispheres. The biomechanics underpinning this sixth sense in birds continue to intrigue researchers.
Unsung Migratory Bird Heroes
While songbirds like warblers and orioles may get top billing, countless less glamorous migratory birds also deserve recognition for their incredible inter-hemisphere journeys, including:
- Shorebirds like plovers, sandpipers, stilts, and oystercatchers enact hemipshere-spanning migrations between inland wetlands and coastal tidal areas.
- Seabirds like shearwaters, jaegers, and albatrosses log staggering ocean migrations spanning from pole to pole.
- Raptors like hawks, eagles, falcons, and vultures ride thermal air currents on monumental continental migrations.
- Waterfowl like ducks, geese, and swans traverse thousands of miles through wetlands and flyways across North America.
- Grassland birds like bobolinks, meadowlarks, and sparrows intrepidly navigate prairie and field networks.
These unsung migratory heroes also merit our support through habitat conservation and the mitigation of human-made hazards. Their collective journeys sustain biodiversity across a hemisphere.
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Conclusion
Summer migration enables an array of spectacular birds like scarlet tanagers, Baltimore orioles, and barn swallows to transform our northern landscapes each year. Following cues like day length and weather patterns, these species execute navigational marvels to reach breeding grounds they’ve likely never visited.
Backyard oases can help provision migrants along their route. But human obstacles, from glass buildings to pesticides, turn journeys into perilous gauntlets. Expanding protected stopover habitats, reducing climate and pollution threats, and sharing the wonder of migration with others will help ensure these voyages continue for generations, reminding us each year of nature’s resilience.