what way do birds migrate

Many birds travel from the Northern to the Southern Hemisphere and back every year, following food resources and friendly climates. But how do seasonal migrants — and other birds such as seabirds undertaking lengthy oceanic foraging trips — find their way?

Young birds from widely ranging species seem to hatch with genetic programming that gives them a basic idea of where they should head when the season changes, and many make their first migration without their parents to help. But as they fine-tune their routes via experience, they rely on a combination of techniques to navigate. The most essential are listed below.

How do birds know when to migrate?

Summer visitors to Britain include a large number of birds that migrate south before winter arrives, joining resident breeders to benefit from seasonal feeding opportunities.

Bird migration patterns are mostly predictable due to the seasonality of the northern summer, which brings with it regular cycles in plant growth and invertebrate abundance. A bird travels in the spring to its breeding grounds, whence it times the hatching of its young to occur when food is most abundant.

A shift in day length signals the start of migration for birds that spend the winter in the temperate zone. However, what about birds that spend the winter in Africa, where day-length variations are less pronounced? How can they predict the weather in their breeding grounds and know when to migrate (either way)?

They don’t; instead, an inbuilt mechanism must regulate when they leave. There is evidence to support the existence of an internal clock, which causes migratory restlessness in captive birds during the time when their wild cousins would be migrating (a condition known as zugunruhe).

How do birds prepare for migrating?

Long-distance migrants benefit from a number of adaptations, including pre-departure fuelling; even wing-feeding species may store fat.

Internal organ sizes can also change: the heart and flight muscles grow larger, while the stomach, liver, and intestines get smaller. When the bird stops over, these modifications could be undone, allowing it to seamlessly transition between its flying and feeding modes.

An 18g garden warbler, for instance, can more than double in weight to 37g prior to departure. During the journey the warbler may lose 3–3. 5g for every 1,000 kilometers traveled, burning protein and fat, the latter primarily from the liver and muscles in the legs as well as the digestive tract.

Extreme changes occur in waders that migrate great distances. For example, the bar-tailed godwit, which can migrate up to 11,000 km, can be up to 55% fat when it departs and can absorb up to 25% of its intestine, gizzard, liver, and kidneys during its migration.

Familiar Sights and Smells Help During Bird Migration

One of the simplest ways a bird can make sure its on the right track — at least while migrating over land on a clear day — is to watch for familiar landmarks below. Some ornithologists believe that day-migrating birds keep an eye out for features such as rivers and mountain ranges, using them to plot a course. Theres even evidence that night-migrating birds can fine-tune their course based on rivers as they near their destinations.

what way do birds migrate

However, what about birds without landmarks to guide them? Seabirds, for instance, occasionally soar over the featureless ocean for great distances. Some birds have the amazing ability to follow their noses.

For a 2017 study, researchers temporarily blocked the sense of smell of a group of seabirds called Scopolis Shearwaters by washing their nasal passages with an otherwise harmless chemical called zinc sulfate. Then, they tracked the birds with GPS devices while they foraged off the coast of Spain, comparing them with shearwaters that could still smell. The test group continued to navigate effectively over land — but when they headed out to sea, they became disoriented, suggesting that scents fill in the gaps when landmarks arent available.

FAQ

Do birds migrate east or west?

Longitudinal migration sees birds flying from east to west, or vice versa. This pattern of migration is less common than north/south migrations, but it does occur. Many European birds follow this pattern. In the US, many songbirds are adopting this migration pattern because of climate change.

Do all birds go south for the winter?

Not all birds migrate, but the majority of birds do. In fact, in North America about 75% of birds migrate. They do this for various reasons, for example, to find a more abundant source of food or a better climate. The Baltimore Oriole, one of our focal species found along the east coast, migrates south in the winter.

What are the migratory routes for birds?

Four bird migration superhighways—the Atlantic, Mississippi, Central, and Pacific—span the length of Canada and the United States. As a concept, flyways help us make sense of bird migration patterns, although, in reality, they have no precise boundaries.

How do birds know which direction they are going?

Migrating birds use celestial cues to navigate, much as sailors of yore used the sun and stars to guide them. But unlike humans, birds also detect the magnetic field generated by Earth’s molten core and use it to determine their position and direction.