Migratory Routes and Patterns
Journeys Across the Globe
Each year, billions of migratory birds switch between spring/summer breeding grounds and overwintering grounds, although their movements vary greatly between species and populations. Their journey may be just a few miles into a nearby valley or thousands of miles across the breadth of an ocean, but no matter the route, these birds rely on seasonal migrations for survival.
While some birds undergo somewhat random and nomadic movements, many follow highly predictable routes year after year, so identifying and protecting these pathways is increasingly important for bird conservation in the modern world.
This guide introduces the fascinating secrets of bird migration routes and patterns. Read along with us to learn about the eight major flyways and much more!
Pictured: A small flock of Barnacle Geese in-flight
Understanding Migratory Routes
Definition and Importance
A migratory route is the pathway birds choose to move between their breeding and overwintering grounds. These may be very direct where long-distance water crossings are involved, but many other factors come into play for birds migrating over land.
Many birds select routes that avoid major obstacles like ocean crossings, high mountains, and habitats that don’t provide their natural food sources.
Other birds choose routes that follow specific habitats, and large soaring birds like Golden Eagles may take advantage of certain features like mountain ridges to assist their flight.
Pictured: A Golden Eagle. A migratory route is the pathway birds choose to move between their breeding and overwintering grounds
Major Migratory Routes
Flyways
Most medium and long-distance migrants move between high and low latitudes to take advantage of the changing seasons. The major migratory routes between these areas are simplified into units known as flyways. Each flyway includes the breeding range, migratory path, and overwintering range of the latitudinal migrants that use them.
Continue reading to learn about the world’s eight major flyways.
North & South American Flyways
Many North and South American birds are latitudinal migrants that move north and south, either crossing between the continents or remaining on either one. These migratory birds typically use the following important migratory routes or flyways:
Pacific Americas Flyway
The Pacific Americas Flyway passes through 18 countries, running from Alaska in the north and along the west coast of the United States, passing through Mexico and reaching Chile in South America. This flyway is used by many bird species, including the Surfbird and the Violet-green Swallow.
Central Americas Flyway
The Central America’s Flyway extends through 27 countries from the Arctic zones of Canada in North America to the Southern tip of South America, passing through Central America and the central regions of each continent. This flyway is used by over 380 different bird species, including the Whooping Crane and the Buff-breasted Sandpiper.
A Surfbird standing on a rocky mountain close to the shore
A family of Whooping Cranes, two adults, and one juvenile (middle), preparing for take-off
Atlantic Americas Flyway
The Atlantic Americas Flyway is used by nearly 400 bird species, including familiar birds like the Baltimore Oriole and Summer Tanager.
This important flyway extends along the East coast of North and South America, from Greenland to the southernmost tip of South America.
Crossing between the continents involves following the coast of the Gulf of Mexico or crossing the open ocean, with or without stops in the Caribbean.
The four flyways of North America
While the three flyways mentioned above link migrants between North and South America, four flyways are typically recognized in the United States. From west to east, these are the Pacific Flyway, the Central Flyway, the Mississippi Flyway, and the Atlantic Flyway.
Close-up of a Baltimore Oriole perching on a branch
The Summer Tanager is a medium-sized songbird
Eurasian Flyways
Over in Europe, Asia, Africa, and Australia, birds follow broadly similar north/south migration patterns to those seen in the Americas. These migrations may occur within each continent or see birds travel extraordinary distances between East Asia and the Southern tip of Africa or even from Western Alaska to New Zealand.
Continue reading to learn about the major Old-World flyways.
East Atlantic Flyway
The East Atlantic Flyway is used by about 300 hundred bird species and connects about 75 countries on four different continents.
This migratory pathway brings birds from the Arctic of Canada and Greenland in the west and Northern Russia in the east to the United Kingdom and other parts of Europe. It also connects Europe with Western and Southern Africa.
Black Sea & Mediterranean Flyway
This flyway connects Northern Asia and Central and Southern Europe with much of Africa and Madagascar. About 300 bird species use this massive flyway, which includes roughly 100 countries.
Long-distance migrants using this flyway may cross the Mediterranean Sea into Africa or use the Isthmus of Suez in Egypt to avoid a water crossing.
Pictured: A European Honey Buzzard - this species migrate south for the winter to sub-Saharan and southern Africa
East Asia/East Africa Flyway
About 331 bird species use this flyway linking Southern, Central, and Eastern Africa with Asia and even Alaska. Birds that use this route include long-distance migrants that travel the entire length of the flyway, as well as intra-African migrants that move between Eastern and Southern Africa.
Central/South Asian Flyway
This short flyway links central and northern Asia with the Indian Subcontinent in the south, remaining within the boundaries of the world’s largest continent.
Birds that migrate along this flyway must negotiate the Himalayas, which are the highest mountains on the globe. Some of the over 300 species that use this route circle around the Himalayas, while others fly directly over this formidable barrier.
East Asian/Australasian Flyway
Nearly 500 species migrate along this far eastern flyway that extends from the Arctic zones of Alaska and Eastern Russia in the north and New Zealand in the south.
Species that move between these continents must make ocean crossings ranging from a few hundred to several thousand miles!
Nearly 500 species migrate along this far eastern flyway which include the Bar-tailed Godwit (pictured)
Bird Corridors
Natural habitats vary across the landscape due to various factors, including altitude, local weather patterns, geology, drainage, and, increasingly, human development.
Bird corridors link areas of suitable habitat and create suitable pathways for migratory birds at a much finer scale than flyways.
Migrating birds may follow natural corridors such as mountain ranges or wooded river courses in arid areas. Managed corridors of natural habits through fragmented urban, agricultural, and industrial areas may provide safe passage for migratory birds passing over-developed areas.
Pictured: A Prairie Merlin. Migrating birds may follow natural corridors such as mountain ranges or wooded river courses in arid areas
Patterns of Migration
Cyclical Patterns
Bird migrations are generally highly cyclical, with well-defined nesting seasons, overwintering periods, and predictable migration times and routes between these important life stages. These natural rhythms and routes have evolved to maximize the bird's chances of successfully reproducing and then surviving the periods of migration and overwintering.
The timing of their movements may vary slightly due to natural variations, but bird movements are generally guided by hormonal changes, day length, and predictable patterns like snowmelt, the thawing of waterbodies, the budding of deciduous plants, and the emergence of insects.
Navigational Patterns
How birds stay on course during migration has long fascinated ornithologists, and through clever scientific study, some of the secrets of bird navigation have been revealed.
Birds navigate using a combination of cues, including:
- Position of the Sun
- The center of rotation in the night sky
- The Earth’s magnetic fields and intensity
- Memory of landmarks
- An innate sense of direction
While rapid changes in the environment may impact a bird's ability to navigate by landmarks, they have less impact on their other navigational techniques. Failing to adapt could cause birds to stick to migratory routes that pass through areas with fewer and fewer resources.
Pictured: Flock of Canada Geese during migration
Conservation of Migratory Routes
Threats to Migratory Birds
Migration is an essential behavior for a large proportion of the world’s birds, although their journey is filled with dangers like predation, exhaustion, and extreme storms.
The impacts of human population growth and development have put increasing pressure on birds by damaging their habitats. Habitat destruction and fragmentation are particularly harmful to migratory birds because many rely on specific environments throughout their migration paths.
Climate change also affects migratory birds negatively by altering their habitats and the timing of seasonal events like insect emergence and plant budding.
These events are critical in the breeding cycle of migratory birds, and arriving late at their breeding grounds can increase competition and decrease their chance of successful reproduction.
Conservation Efforts
At a local level, conserving migratory birds requires focused efforts to protect important habitats along flyways and corridors. This includes everything from growing native plants that support hungry Hummingbirds to engaging with landowners and the proclamation and management of protected areas.
On a broader scale, the conservation of migratory birds requires collaboration between various nations, both neighboring and distant.
International conventions like the Migratory Bird Treaty Act and the CMS (Convention on the Conservation of Migratory Species of Wild Animals) promote cross-border conservation.
Pictured: A Rufous Hummingbird. Conserving migratory birds requires focused efforts to protect important habitats along flyways and corridors
Summary
Whether skirting mountains, following river courses, or committing to long open-water crossings, migratory birds are on the move all across the globe.
Various bird species have evolved to use different migratory pathways and corridors, both within political boundaries and across continents.
However challenging it may be, it’s vital that natural habitats all along the length of these flyways are protected if migrating birds are to survive.