Those who have seen it know what a beautiful sight it is — hundreds, even thousands, of birds flying together, sometimes in perfect formations. Do you know where they are flying to and why?
It is definitely not their usual flight in search of food. These are migratory birds on the way to or from their seasonal destinations, or you can say that the flight is part of their annual migration.
Why do birds migrate?
There are several reasons for birds to migrate, but first a few words on what migration is. Birds usually go from the cold northern hemisphere, where they nest during the milder season, to more temperate southern areas when winter becomes harsh. The migration is both ways, not just north to south but also from south to north.
Birds migrate for various reasons, but at the centre of it all is the need for survival. In winter, when food supplies become scarce because of cold and snow, and birds are at risk of starvation, they leave their homes for areas that have abundant food. After some time, when the season changes and food sources begin to dwindle there, they make the journey back to their homes where food supplies have replenished with the change in season again. If they wouldn’t migrate, more birds would be competing for the scarce food available at home.
Since most birds breed in winter, they need a habitat that provides adequate shelter and more favourable climate. Also breeding in groups provides better protection from predators than individual parents can. Many birds migrate to habitats that are inaccessible to predators, such as cliffs or rocky offshore islands.
There are some species of birds which cannot survive the cold temperatures because of their plumage and have to migrate to more temperate habitat. Then there are those living in hot climate and have to move to cooler northern areas as the hot tropical environment is not suitable for them to raise chicks.
While for more than half of the world’s birds, it is essential to migrate to stay alive, but there are still those in the cold north which do not migrate. Surprisingly, over the centuries, these species have learned to survive on various foods available in winter and some have even adapted to cold climates by having thicker fat reserves and heavier feather insulation needed for cold weather.
How do birds navigate?
When we go anywhere, we take the help of Google Maps, compass and other such aids, but birds make these journeys of thousands of miles annually without maps, road signs or smart phone apps, depending just on their instincts year after year. So, how do these birds manage to find their way to their destinations? We know that they do not just randomly migrate to any place they find, but each species has specific destinations which they visit each year.
Scientists believe that birds use a combination of several different types of innate biological senses and experience for this purpose. Many birds have special chemicals or compounds in their bodies that help them sense the Earth’s magnetic field, which helps them find the right direction for long journeys. In other words, they have some internal compass to guide them. They also have a built-in mechanism to gauge the position of the stars and the sun above the horizon, which help them navigate their route.
Since birds follow the same routes every year, their keen eyesight also helps them to move in the right direction through different landforms and geographical features, such as rivers, coastlines, and mountain ranges. Travelling in flocks, the younger ones learn the routes from the adults and follow the same route themselves the next year.
It is not that birds take off from their winter homes and continue without break till they reach their summer destinations, or vice versa. Of course, they have to break their journey for food and rest. For this too, they have specific destinations.
On their flyways (the path that migratory birds take while moving between their winter and summer destinations) they know specific locations that provide their preferred type of food essential to their survival. The birds land there, rest and feed for a few days to replenish their energy and again take off. Many small birds take different routes in spring and fall in order to take advantage of seasonal patterns in weather and food.
Migratory birds in Pakistan
As we all know Pakistan is blessed with beautiful landscape, waterways, wetlands and other natural resources. This attracts migratory birds for they know it will provide them enough food and also breeding sites.
Pakistan is among the 30 countries of North, Central and South Asia, and Trans-Caucasus that are covered by the Central Asian Flyway, one of the seven flyways around the globe used by migratory birds.
Central Asian Flyway, which is also known as Green Routes or Indus Flyway Zone, covers the huge Eurasian continental areas between the Indian Ocean, Arctic Ocean and islands linked with these oceans, and comprises several important migration routes of water-birds, most of which extend from Serbia to West Asia, India and the Maldives.
While some migratory birds spend their winter in Pakistan, some only make a small stopover to replenish their energy by rest and food, before moving further south.
Migratory birds take various routes to come to Pakistan. Most birds arrive at the end of August and leave in February. Some arrive from Siberia, over the Karakoram, Hindu Kush and Suleiman Ranges along the Indus River, and move down to the delta through the Indus Flyway. Birds from China and Russia cover a distance of 4,500 kilometres by using the Indus Flyway to reach Pakistan.
These migratory birds stop at wetlands and water bodies in Pakistan. Key wetland sites include Mangla Lake, Rawal Lake in Margalla Hills National Park, Zangi Nawar Lake, the high mountain wetlands in northern Pakistan, including the Naltar wetland complex, and the wetlands of Deosai National Park plains.
Many bird species also stay at Hamal, Drigh, and Langh lakes for feeding and breeding purposes. Some make a short stay at Thar and Thatta, before moving on further south. Hadero, Keenjhar, Haleji lakes are some of their main breeding sites.
Common species of migratory birds in Pakistan
Migratory birds of Pakistan include various species of ducks and waders, such as mallards, northern shoveler, common teal, common pochard, stints, besides cranes, geese, flamingos, swans, falcons, gulls, plovers, snipes, cormorant, skuas and jaegers, storks, etc. There are also houbara bustard, pintail, spoon bills, raptors, snipe, pelican and passerines such as warblers, pipits and buntings.
While migratory birds are important for the ecology and tourism industry, for many reasons the population of migratory birds that used to move towards Pakistan has declined over time. Though illegal, hunting, poaching and netting are major causes of decrease in the population of migratory birds coming to Pakistan.
Due to merciless hunting, the population of some duck species, including white-eyed pochard, marbled teal, and garganey, has drastically decreased. Cranes, because of their size and beauty, unique calls and complex behaviour are hunted and trapped during their migration in Khyber Pakhtunkhwa and Balochistan. Houbara bastard has been hunted to such an extent that it has been declared critically endangered and is globally protected.
Some interesting facts
• At least 4,000 species of bird are regular migrants, which is about 40 percent of the total number of birds in the world.
• Before migration, many bird species build a greater fat supply to provide extra energy for their travels — the process is known as hyperphagia. For example, ruby-throated hummingbird and blackpoll warbler almost double their body fat just a week or two before migration. The blackpoll warbler flies 2,300 miles non-stop for 86 hours.
• Old, ragged feathers create more wind drag and air resistance, which requires a bird to use more energy in flight. Many birds moult (shedding old feathers to make way for new feathers) just prior to migration to take advantage of more aerodynamic feathers that make flight easier and more efficient.
• The tiny Arctic tern makes the longest migration in the animal world. It travels 49,700 miles in a year between their Arctic breeding grounds and the Antarctic coast.
• Hummingbirds are not only the smallest migrating birds, measuring 7.5-13 centimetres in length, they are also the only known birds that can fly backward.
• Bar-headed geese are the highest-flying migratory birds, regularly reaching altitudes of up to five and a half miles above sea level while flying over the Himalayas in India. However, the Ruppel’s griffon vulture, holds the record for the highest altitude ever; it collided with a plane at 37,000 feet in 1975 and was unfortunately sucked into its engine.
• The great snipe holds the award for fastest bird. It flies around 4,200 miles at speeds of up to 60mph! No other animal travels at such speeds for such long distances.
• The bar-tailed godwit can fly for nearly 7,000 miles without stopping, making it the bird with the longest recorded non-stop flight. During the eight-day journey, the bird doesn’t stop for food or rest.
• Even birds that don’t fly, do migrate. Emus, the large Australian birds, often travel for miles on foot to find food, and many populations of penguins migrate by swimming.
• There are species of birds that cross an ocean during their migration route (transoceanic migrants), and they typically remain in the air for up to 100 hours before taking a break on land!
• Most migratory bird species are equipped with long, pointed wings, giving these species a more aerodynamic design for an efficient and safe flight.
— Compiled by RN
Published in Dawn, Young World, May 14th, 2022