The Basics of Bird Migration: How, Why, and Where | All About Birds

The Basics of Bird Migration: How, Why, and Where | All About Birds

The Basics of Bird Migration: How, Why, and Where | All About Birds

Geese winging their way south in wrinkled V-shaped flocks is perhaps the classic picture of migration-the annual, large-scale movement of birds between their breeding (summer) homes and their nonbreeding (winter) grounds. But geese are far from our only migratory birds. Of the more than 650 species of North American breeding birds, more than half are migratory.

Why do birds migrate?

Birds migrate to areas of low or decreasing resources to areas of high or increasing resources. The two primary resources being sought are food and nesting locations.

Birds that nest in the Northern Hemisphere tend to migrate northward in the spring to take advantage of burgeoning insect populations, budding plants and an abundance of nesting locations. The winter approaches and the availability of insects and other food drops, the birds move south again. Types of migration The term migration describes the most important species of the species, including hummingbirds, canes and freezing temperatures, as well as adequate food supplies.

Types of migration

periodic, large-scale movements of populations of animals. One way to look at migration is to consider the distances traveled.
  • Permanent residents do not migrate. They are able to find adequate supplies of food year-round.
  • Short-distance migrants move only a short distance, from higher to lower elevations on a mountainside.
  • Medium-distance migrants cover distances that span from one to several states.
  • Long-distance migrants typically move from breeding ranges in the United States and Canada to wintering grounds in Central and South America. Despite the arduous journeys involved, long-distance migration is a feature of some 350 species of North American birds.

The pattern of migration may vary within each category, but most variable in short and medium distance migrants.

Origins of long-distance migration

For birds that winter in the tropics, it seems strange to imagine leaving home and embarking on a migration north. Why make such an arduous trip north in spring? One idea is that through many generations the tropical ancestors of these birds dispersed from their tropical breeding sites northward. The seasonal abundance of insect food and greater day length allowed them to raise more young (4-6 on average) than their stay-at-home tropical relatives (2-3 on average). Their breeding zones moved north during periods of glacial retreat, the birds continued to return to their tropical homes and the winter weather and declining food supplies made life more difficult. What triggers migration?

zugunruhe , meaning migratory restlessness. Different species of birds and even segments of the population within the same species may follow different migratory patterns.

How do birds navigate?

Migrating birds can cover thousands of thousands in their annual travels , often traveling the same course year after year with little deviation. First-year birds often make their first migration on their own. Somehow they can find their winter home despite never having seen it before, and return the following spring to where they were born.

Some species, particularly waterfowl and cranes, follow preferred pathways on their annual migrations. These pathways are often related to important stopover locations that provide critical food to the birds' survival. Smaller birds tend to migrate in broad fronts across the landscape. Recent studies using eBird are revealing that many small birds take different routes in spring and fall, to take advantage of seasonal patterns in weather and food.

Migration hazards

Taking a journey that can stretch to a round-trip distance of several thousand miles is a dangerous and arduous undertaking. It is an effort that tests both the birds' physical and mental capabilities. The physical stress of the trip, lack of adequate food supplies along the way, bad weather, and increased exposure to predators all add up to the hazards of the journey.

In recent years long-distant migrants have been facing a growing threat from communication towers and tall buildings. Many species are attracted to the lights of tall buildings and millions are killed each year in collisions with the structures. The Fatal Light Awareness Program, based in Toronto, Ontario, Canada, has more about this problem.

Studying migration

Each spring, about 500,000 Sandhill Cranes and some endangered Whooping Cranes use Nebraska's Platte River as a staging habitat during their northward migration.

Scientists use several techniques in studying migration, including banding, satellite tracking, and the relatively new method involving lightweight devices known as geolocators. One of the goals is to locate important stopover and wintering locations. Once identified, steps can be taken to protect and save these key locations.

Giant live oak trees, like these in High Island, Texas, attract many of our most beautiful birds after their spring journey across the Gulf of Mexico. Clockwise from top left: Baltimore Oriole, Indigo Bunting, Chestnut-sided Warbler, Bay-breasted Warbler, Blue Grosbeak, Scarlet Tanager, Black-throated Green Warbler, Orchard Oriole, Black-and-white Warbler.

Some places seem to have a knack for concentrating migrating birds in larger than normal numbers. These "migrant traps" often become well known as birding hotspots. For example, small songbirds migrating north in the spring fly directly over the Gulf of Mexico, landing on the coastlines of the region.

Gulf Coast states. When, storms or cold fronts bring headwinds, these birds can be near exhaustion when they reach land. In these cases, they are likely to be very popular with birders, even if they do not exist in the United States. earning international reputations.

Peninsulas can also concentrate migrating birds as they follow the land and then pause before launching over water. Spring migration is an especially good time for those who have a lot of experience in the area. feed birds in their backyard to attract species they normally do not see. Offering a variety of food sources, water, and adding natural food sources to the landscape can make a backyard attractive to migrating songbirds.

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