Migration of birds is a natural practice in the life cycle of birds. Different species of birds fly hundreds and thousands of kilometers to find food and a safe sheltered place to nest and breed for their survival. Birds require specific and richest environmental resources for reproduction and to raise their young. When the conditions at the breeding sites become unfavorable, migrating birds adapt to the seasonal changes and fly to the regions where the climatic conditions are better.

Birds possess the streamlined body, lightweight skeleton, hollow bones, well developed pectoral muscles, and wings provide them the power of flight. Birds have a large four-chambered heart with a rapid heartbeat ranging from 500 beats per minute in small songbird to 1,000 beats per minute in hummingbird which fulfills the metabolic requirement of flight. Their lungs also remain inflated all the time.

Migration is seasonal and the birds start migrating when the tailwind is favorable. Birds migrate normally at high altitudes because of the prevailing winds and the cold at the altitudes which helps them to disperse heat generated by flight muscles. Most songbirds migrate at 500 to 2,000 meters, but some fly as high as 6,800 meters; swans have been recorded at 8,000 meters and Bar-headed Geese at 9,000 meters. The longest migration is undertaken by the Arctic Tern who breeds on Arctic North in summer and flies to Antarctica to spend winter covering the distance of nearly 15,000 km.

Different migrating birds follow different migration patterns, routes and times. Some species of migrating birds are highly social during migration and move in flocks while some species migrate in solitary fashion. Flocked migrants are day migrants and most noticeable. The flock consists of family groups. Flocked migrants include water birds like puffins, ducks, cranes, geese, pelicans, auks and sandpipers and land birds like larks, crows, swifts, doves, blackbirds, pipits and waxwings. Birds that migrate in a solitary manner include woodpeckers, owls, hummingbirds, cuckoos, hawks, herons, kinglets, orioles and wrens.

Scientific studies suggest that birds navigate and find their way from one location to the other through different techniques. Birds orient themselves through magnetic sensing of north, geographic mapping by visual laying out of the land, the smell of the sea, the sound of the shores, winds in the mountain ranges, star orientation positioning of stars and their constellation, learning routes birds like snow geese and cranes learn migration routes from their parents.

Migration is a risky journey and involves a wide range of threats. They face natural obstacles like storms and bad weather. Due to human activities, migrating birds are exposed to dangers and threats. The destruction of habitats due to deforestation, draining of wetlands, pollution of sea and air, agriculture, grazing, etc. are the main threat migrating birds faces, as there is loss of stopover sites and breeding and wintering grounds. Man-made formations like skyscrapers and lighthouses distract and mislead them.