Bird Migration in the U.S.: Top Questions Answered

Migration is the seasonal movement of birds. The main purpose of their migration is survival. They travel in search of food and also to breed. These travelers cover vast distances across the United States and beyond.

Yet for many of us, a lot of questions remain. This article covers all the questions with detailed answers to solve the mystery behind birds migrations. Let's talk about them.

1. Why Don't All Birds Migrate?

Migration is a risky journey and it needs energy. In North America, one quarter of species stay because they find everything locally. So, if birds find everything in one place, they don't need to migrate. They avoid hazards.

Every species of birds has different metabolisms. They have different needs for food, breeding and different effects of the environment on them. Some birds survive warm environments and some do not and the same with cold environments. For example, Black-capped Chickadees in Canada’s boreal forests can survive harsh winters by eating insect eggs and other hidden food in tree bark. Hence, they don’t have to fly south.

2. When Do Birds Migrate And What Factors Influence the Timing?

Most birds travel twice a year in the U.S.. One in spring to find their breeding ground and one in late summer or fall to wintering areas. They predict their migration timing with daylight length, called as photoperiods. They sense the change in seasons due to the hormonal changes in them. These changes spark zugunruhe, or migratory restlessness, signaling that it’s time to migrate

Many species are consistent. For instance, people saw flocks of Red-winged Blackbirds in the same region within the same two-week window each year.

Moreover, the timing of birds migration is not rigid. Weather and climate conditions are the main factors that can affect their timing and success. Birds may delay migration if storms or cold fronts roll in, or depart a bit early if temperatures and food availability prompt them.

3. What Routes Do Migratory Birds Take Across the U.S.?

The pathways that migratory birds use across the continent are called flyways. In North America, there are four main routes. They are from North to South. 

These routes are:

1. Atlantic Flyway along the East Coast

2. Mississippi Flyway down the Mississippi River valley and the central U.S.

3. Central Flyway through the Great Plains

4. Pacific Flyway along the West Coast

These routes offer good stopover habitat and food. Many songbirds and waterfowl funnel along the Mississippi River corridor or hug coastlines where wetlands and food are plentiful. Some species stick tightly to these corridors (waterfowl are well-known for using specific flyways). On the other hand, others spread more broadly, mixing between flyways at the edges.

4. How Far Do Birds Travel During Migration?

The distance birds travel varies from a few miles to the longest. Some birds are short distance migrants and they move only a few hundred miles south to find milder wintering spots. While some are long distance migratory birds. These birds routinely cover thousands of miles.

Many warblers, orioles, and other songbirds fly from North America to Central or South America. They travel a distance of 2,000–5,000 miles or more each fall. A few species are true globe-trotters. The Arctic Tern famously migrates from the high Arctic to the Antarctic and back every year. It is a round trip of over 50,000 miles. It is the longest migration of any bird on Earth. Another record-holder is the Bar-tailed Godwit. It flies 8,100 miles nonstop over the ocean from Alaska to New Zealand without a break.

5. What Are the Biggest Challenges Birds Face During Migration? 

Migration is the most challenging part of a bird's life. They have to fly to survive. During migration, they continuously fly in search of a safe place to rest and refuel. Sometimes they find no place to land and feed. They are at risk of starvation and fatigue. Bad weather is also a major risk. The heavy rains, winds, storms and fog disorient them and force them into areas with unfavorable conditions. Further, predators like hawks and outdoor cats prey on tired birds.

Human made threats are a huge reason for the deaths of thousands of traveling birds each year. Bright lights, glass, and windows in urban areas confuse the birds at night. Other obstacles like communication towers, wind turbines, and even passing aircraft can be fatal. The urban development means habitat loss and few stopover sites for birds.

6. How Do Birds Navigate During Migration?

Migratory birds use innate instincts and environmental cues to navigate. They can orient themselves by the sun and the stars. An experiment with indigo buntings in planetariums showed that these birds set their migratory direction based on star patterns in the night sky.

Birds also have an internal magnetic compass. It consists of special light sensitive proteins in their eyes called cryptochromes. This compass helps them to detect Earth’s magnetic field. Due to this ability, they can see the direction of magnetic north and south in darkness. It also helps them to fight the challenges like cloudy nights.

In addition, birds use familiar landmarks and smells to navigate. Many species memorize the geography of their route. They follow coastlines, river valleys, or mountain ranges and recognize key stopover sites from previous trips.

7. How Does Climate Change Affect Bird Migration in the U.S.?

Climate change affects the timing of the birds migrations. Due to the rise in temperature of the earth due to multiple human activities, the spring season has begun to become hotter earlier than expected. Due to early springs, the food (Insects and flowers) for migrating birds is also available earlier.

Hence, the birds arrive at their breeding site a bit late. They face a scarcity of food (caterpillars and Berries)  and may also unfavorable environment to breed. This mismatch in timing decreases the survival rate and breeding success of the birds.  

Extreme weather can destroy important habitats or kill birds during migration. The rising sea levels flood the wetlands and beaches. Coastal migratory birds face threats due to the destruction of their habitat.

8. What are Some Ways People Can Help Migratory Birds?

We can help migratory birds with some safety steps. The following are some important steps:

● We should control the light in urban areas during peak migration seasons. For example, dim the lights at night

● To prevent window collisions is also another way. We should make glass windows bird friendly. For this, use decals, external screens or patterned tape that birds can see.

● We can create bird-friendly habitat. Plant native trees, shrubs, and flowers that supply berries, seeds, and insects for birds.

● Support organizations that make efforts to preserve natural habitats. Make donations to organizations that are making efforts to build new forests.

9. Why Do Some Birds Return to the Same Place Every Year? 

Many migratory birds return to the same location every year. This is called site fidelity (or philopatry). If the birds find one area safe and productive, they prefer to come back to that region every year. According to the local knowledge hypothesis, birds rely on their knowledge of local food sources, shelter and predator risks.  

10. How Do Scientists Study Bird Migration?

There are different methods to study the birds migrations. Bird banding is the most ancient method. A small numbered ring is attached to the bird's legs in this method. The band on the leg shows where birds travel.

Radar and satellite technology are other methods. Weather radar provides images of the birds migrating at night. Satellite GPS telemetry devices also help analyze the migration of larger birds, like raptors or shorebirds. Scientists use lightweight geolocators and radio tags for small birds.

Let's Protect the Migrating Birds

The awareness of birds migration can save their habitats and food sources. It will increase their survival and breeding rate. We should learn and share that knowledge. Our small actions can save the future generation of birds. 

*Visuals courtesy of free image sources