Bird migration is the regular seasonal movement of birds between breeding and wintering grounds. Many species of birds migrate long distances each year, traveling thousands of miles between their summer breeding grounds and wintering areas. There are a number of reasons birds migrate such long distances each year.
Why do birds migrate long distances?
There are several key reasons birds undertake these incredible journeys each year:
- Food availability – Birds migrate to areas where food is more plentiful at different times of year. Many species time their migration to coincide with peaks in food availability.
- Breeding habitat – Birds migrate to habitats that are best suited for breeding and raising young. The conditions at their wintering grounds may not be suitable for breeding.
- Weather and climate – Birds escape harsh weather and climate conditions by migrating. Freezing temperatures, drought, etc. may make survival difficult.
- Length of daylight – Increasing or decreasing daylight hours trigger migratory instincts in many species and cue them to move between breeding and wintering grounds.
By migrating, birds are able to take advantage of seasonal food resources, find the best areas for breeding, and avoid extremely cold winter conditions or hot summer conditions. Their amazing ability to navigate over vast distances allows them to exploit resources across continents and hemispheres throughout the year.
What are some well-known long distance migrations?
Some of the most incredible long distance migrations include:
- Arctic Tern – Breeds in the Arctic and winters in the Antarctic. Undertakes a migratory journey of over 40,000 miles each year, the longest migration of any bird species.
- Bar-tailed Godwit – Migrates non-stop for 6,800 miles from Alaska to New Zealand, one of the longest known non-stop flights.
- Ruby-throated Hummingbird – A tiny bird that makes a 2,000 mile journey across the Gulf of Mexico between Canada and Central America.
- Osprey – Travels 5,000 miles between breeding grounds in North America and wintering grounds in South America.
- Hudsonian Godwit – Believed to make the longest overwater journey by a non-pelagic bird, flying non-stop for 4,000 miles over the Pacific Ocean between Alaska and New Zealand.
These marathon migrations demonstrate the incredible endurance and navigational abilities of birds. Traveling thousands of miles over oceans, deserts, and mountain ranges, these global travelers complete some of the most amazing feats of migration in the natural world.
What are the main flyways for migration in North America?
There are four major north-south migration flyways used by birds in North America:
- Atlantic Flyway – Along the Atlantic coast from Maine to Florida and eastern Gulf of Mexico
- Mississippi Flyway – Follows the Mississippi River valley from northern Canada to the Gulf of Mexico
- Central Flyway – Between the Rocky Mountains and Mississippi River from Canada to Texas
- Pacific Flyway – Along the Pacific Coast from Alaska to South America
These flyways generally follow major geographical features like coastlines, mountain ranges, and river valleys. They provide important stopover habitats for food and rest during migration. Some examples of birds that use these flyways are ducks, geese, shorebirds, raptors, and songbirds.
When does migration occur?
There are two main types of migration:
- Spring migration – Occurs between wintering and breeding grounds from March to May in the northern hemisphere. Birds fly northwards towards breeding areas.
- Fall migration – Occurs between breeding and wintering grounds from August to November in the northern hemisphere. Birds fly southwards towards wintering areas.
Exact timing varies by species and is influenced by factors like weather, food availability, and daylight hours. Short-distance migrants may arrive and depart a few weeks before long-distance Neotropical migrants that winter in Central and South America.
What are stopover sites?
Stopover sites are places that provide food, shelter, and safety for birds to rest and refuel during migration journeys. Quality stopover habitat is critical for migratory birds. Types of stopover sites include:
- Coastal wetlands and beaches
- Inland wetlands
- Riparian woodlands
- Grasslands
- Forests
Habitat loss and degradation at stopover sites from human activities like development, pollution, and climate change threaten migratory birds. Conservation of stopover habitats is crucial for successful migration.
How do birds navigate on migrations?
Birds use a variety of cues and abilities to navigate their marathon migrations:
- Celestial cues – Using the sun, stars, and polarization patterns for guidance.
- Earth’s magnetic field – Detecting magnetic fields to determine latitude and direction.
- Landscape features – Using coastlines, mountains, rivers, etc. as guideposts.
- Smell and memory – Recalling scents and landmarks from previous migrations.
- Circadian rhythms – Internal biological clocks help keep migrating birds oriented.
Researchers continue studying the mechanisms birds use to accomplish these remarkable feats of navigation over thousands of miles. Their ability to return to the same breeding and wintering sites year after year is especially impressive.
What threats do migrating birds face?
Migrating birds face a number of threats and challenges including:
- Habitat destruction – Loss of stopover and breeding habitats.
- Climate change – Shifting temperatures, precipitation, vegetation patterns, etc. can impact timing and resources.
- Pollution – Contaminants at stopover sites can poison birds.
- Artificial light pollution – Disorients migrating birds and causes collisions with buildings.
- Collisions – Communication towers, wind turbines, buildings and vehicles kill many birds.
- Overhunting – Some migratory gamebird species are threatened by unsustainable hunting along flyways.
Conservation measures like habitat protection, reducing emissions, implementing bird-friendly designs, and hunting regulations are needed to address these threats.
| Species | Migration Route | Distance Traveled (miles) |
|---|---|---|
| Arctic Tern | Arctic to Antarctic | 40,000 |
| Ruby-throated Hummingbird | Canada to Central America | 2,000 |
| Bewick’s Swan | Russia to United Kingdom | 2,500 |
| Northern Wheatear | Alaska to sub-Saharan Africa | 9,300 |
| Sooty Shearwater | New Zealand to Japan | 5,000 |
What can people do to help conserve migratory birds?
Some ways people can help protect migratory birds include:
- Supporting habitat conservation efforts for stopover sites and flyways.
- Keeping cats indoors to reduce predation on birds.
- Making windows bird safe using decals or screens to prevent collisions.
- Using bird-friendly coffee and chocolate to help Neotropical migrants.
- Reducing use of pesticides and chemicals hazardous to birds on lawns and gardens.
- Putting up nest boxes and planting native plants to provide food and shelter.
- Drinking shade-grown coffee to help songbird habitat.
- Volunteering for citizen science projects that monitor migratory bird populations.
Even simple actions can make a difference for protecting the amazing migrations birds undertake each year. Supporting conservancy groups, education, sustainable agriculture and proper hunting regulations are also impactful for conservation.
Conclusion
Bird migration is a complex and impressive phenomenon. Understanding the causes, routes, navigation and threats to migration is key for conservation efforts. While birds migrate to take advantage of seasonal habitats and resources, their incredible journeys now face many human-caused hazards. Protecting stopover sites, reducing collisions, and mitigating climate change impacts are vital for helping ensure migratory birds can continue undertaking their marvelous migrations each year.
