How Does Weather Affect Bird Migration?

Some species of birds have an amazing ability to navigate thousands of miles across the globe during yearly migrations — you probably know the score: they fly southward in the winter and northward in the summer. On the other hand, some birds migrate only a short distance, perhaps 20 or 30 miles. The weather plays a role in both kinds of migration patterns.

Why Do Birds Migrate?

An astounding number — between 6 and 8 billion — of birds wing their way into or out of the United States each year! That’s two-thirds of all U.S. bird species. Here are some reasons for all of the ruffled feathers.

Birds React to Their Biology

• A bird’s pituitary gland responds to changes in the length of the day and the intensity of the sun in a yearly cycle. The bird’s thyroid tells it to store fat in preparation for the trip.
• This is hardwired into long-migration birds like the arctic tern, who need the most stored energy for the great distance they cover.

Birds React to Their Surroundings

• Too much competition for the same food supply can deplete resources to the point where birds are forced to look elsewhere for a meal, and this also tends to run in a cycle. An abundant food supply is crucial for newborn arrivals in the nest to thrive.
• Increased human development of an area displaces birds to seek homes elsewhere; this is an example of a short-distance migration that may occur any time of year.
• Shifting food supply patterns require mountain-dwelling birds to seek lower elevations in the fall and higher ones in the spring.

How Does Weather Affect Bird Migration?

Migrating birds have to compensate for changing atmospheric conditions for their protection. Research shows that changing weather conditions influence every bird to some degree.

Temperature Changes Affect the Start of Migration

Wildlife scientists are learning that temperature changes are a primary trigger to get birds in the mood to migrate once the biological changes are in place. Birds tend to follow warmer paths in flight as long as it doesn’t take them too far off course.

Temperature Changes Affect the Migration Route

Each March and April find skies over the Gulf of Mexico filled with northbound spring-migrating birds. A strong cold front meeting such a flock, say, along the Texas coast, will cause an immediate problem. Often, strong cold fronts contain thunderstorms and very gusty winds — if the birds are over the ocean, they could be forced out of the sky and perish.

Other, more fortunate birds will take shelter until the storms pass before resuming their migration trip. A similar pattern takes place farther north, as late-season arctic fronts may force geese and other cold-weather birds to pause for a few days while the extreme cold passes.

Hurricanes and Large Storms Affect Migration

Hurricane winds can cause birds to be driven far off course if they are unfortunate enough to get pulled into a developing storm. For instance, brown pelicans have been found more than a thousand miles inland. Sometimes these birds lack the energy to return to their natural habitat, and they don’t survive.

Hurricanes also damage the habitats of resident birds, which may force them to migrate short distances (less than 100 miles) out of necessity, not instinct. Hurricanes typically happen between June and November, so these are “out of season” migrations.

Bird Migration Routes

Long-distance bird migration routes tend to follow along several “flyways.” Birds use the flyways every year as they travel from their northern spring breeding grounds to their southern wintering sites. Flyway routes are dictated by both geography and available food along the paths.

Pacific Flyway

Many birds using the Pacific flyway spend their summer in the Arctic Refuge of Alaska and then spread out as they head south for the winter. Birds tend to exit this very long flyway at various points along the route. Here is a sample of birds using the flyway to begin their fall migratory trek in Alaska but ending up in very different places:

• Snow Goose: destination California
• Bohemian Waxwing: winters in Colorado
• Northern Waterthrush: heads for the Lone Star State (Texas)

Central Flyway

This route runs from northern Canada all the way to southern Mexico. Birds tend to follow the eastern fringe of the Rockies along the way, probably for navigational aid. Some of the flyway’s passengers include:

• Purple Finch: begin in southern Canada, end in midwest or southern states
• American Robin: some migrate from southern Canada to the Texas border, while others winter at spots along the route.

Mississippi Flyway

This flyway parallels the Central Flyway, only about 500 miles to the east. It generally occurs over the Mississippi River Valley, but extends southward, across the Gulf to Central America, and northward, well into Canada. Here are some of the birds you might sight along the Mississippi Flyway:

• Common Grackle (a real “pest” bird in the southern states!): they tend to migrate to southern Texas or Florida for the winter but may be found anywhere from southern Canada to Iowa in the summer.
• Ruby-Throated Hummingbird: their winter flight takes them all the way to Panama and South America, one of the longest flights of any bird on the Mississippi Flyway. Spring migration finds the species stopping for the warm season anywhere from Texas to Minnesota.

Atlantic Flyway

The Atlantic and Pacific Flyways are the longest, as they both originate above the Arctic Circle and penetrate well into Central America. Birds using the Atlantic Flyway include:

• Blue Jay: spring migration takes them to southern Canada and they winter anywhere from the mid-Atlantic states to Texas.
• Song Sparrow: winters in the Sunbelt states anywhere from Florida to Arizona, the head north during spring migration to the Great Lakes and southern Canada.

Some birds, like the ruby-throated hummingbird and the song sparrow, use several different flyways because they are spread out across the continent. Additionally, temporary weather changes may impact any of these migration routes as birds land or change course to ride out thunderstorms and avoid cold fronts or hurricanes.

Use Weather Technology for Bird-Watching

Since different bird species migrate differently (or don’t migrate at all), you can compare temperature patterns with birds taking flight in fall and spring. The AcuRite Atlas® weather station will monitor the daily temperatures for you. This Wi-Fi connected display will send the data to My AcuRite® for logging weather trends and monitoring temperature fluctuations, allowing you to draw correlations to when different types of birds leave town. Tie the whole scene together and see how local bird activity changes as spring bursts forth with food and flowers for our winged friends!

Steve LaNore is a certified broadcast meteorologist with more than 30 years’ forecasting and technical experience. He has provided meteorological consulting for everything from insurance adjusters to court cases and is a nine-time award-winning author and broadcaster. LaNore has authored two books, available on Amazon. He resides in north Texas near beautiful Lake Texoma.