Nepal, November 23 -- flocks of gulls, a type of bird that nests far in the north, arrived in the Kathmandu Valley last week. Thousands of b...
Nepal, November 23 -- flocks of gulls, a type of bird that nests far in the north, arrived in the Kathmandu Valley last week. Thousands of birds from more than 150 species reside in Nepal or pass through it as a resting point during the winter migration period. The movement of Demoiselle cranes and Bar-headed geese, which fly over the towering Himalayas, has intrigued many scientists and nature enthusiasts. In his book High Adventure, Sir Edmund Hillary describes witnessing birds above Mount Everest while climbing toward the peak.
Each spring, billions of birds gather to undertake their yearly trip to their northern breeding areas. They spend approximately 3-4 months on this challenging journey back to where they spent the winter. This amazing event involving our feathered companions is referred to as bird migration. In recent decades, research on bird migration from different parts of the world has provided insights into why, how, and when these birds travel. Nevertheless, just under 100 years ago, scientists were confused about the idea of birds traveling thousands of kilometers.
The first instance of this confusion dates back to the era of the Greek philosopher and scholar Aristotle. One of the explanations Aristotle proposed was that birds changed into another species during winter, and when spring arrived, they returned to their original form! Jumping ahead about 1,500 years, people continued to believe that birds hibernate in the winter, similar to amphibians. The earliest suggestion pointing towards a longer, exhausting migration in birds was made by Charles Morton, who claimed that birds traveled to the moon during the winter and returned to Earth in the spring.
One lucky evening for Ornithology and a sorrowful one for a White stork in 1822 in a small German town altered the way people understood what birds do during the winter months. A white stork was shot in that village; it was an unusual stork with a wooden spear lodged in its neck. This spear originated from African wood, indicating that the bird had been in Africa. It marked the first real evidence that birds actually travel south during the winter.
In 1899, Hans Mortensen used metal rings to tag European Starlings in order to monitor their movements, thus initiating the scientific practice of bird banding. This completed the last part of the puzzle in determining if birds migrate.
Approximately 42 years later, in the war-torn United Kingdom, two biologists based at a camp responsible for monitoring radar to detect enemy fighter planes repeatedly encountered strange signals on their radar. They would alert the base, thinking it was an enemy ship; however, the signal would quickly disappear. After this occurred over time, they developed a method to recognize these unknown threats, which they referred to as "Angels" or "Ghosts." The straightforward approach was to use a telescope to look at the sky whenever they detected a radar signal. Fortunately for science, these turned out to be birds!
By the middle of the 1900s, it was established that birds migrate; yet, researchers continued to discover the reasons and mechanisms behind this behavior.
Some researchers proposed that birds travel during the night, sparking debate within the field of bird science, as others argued that birds should migrate during the day when visibility is better. The only way to confirm this was to watch them at night during the busiest migration period. That's precisely what George Lowery, an ornithologist from Louisiana, did. In 1880, William Scott noted seeing birds outlined against the moon while using a telescope. Applying the same method, Lowery studied the night sky from Yucatan and found that birds do indeed migrate at night, crossing the Gulf coast instead of sticking to land routes.
In 1957, ornithologist Richard Graber and engineer Bill Cochran worked together to capture the sounds of birds that are active at night, using a bicycle axle and 6,000 feet of recording tape. Approximately 80 percent of migratory birds are known to travel during the night, and they have distinct calls made while flying. By 1965, Richard Graber had begun using a radio transmitter to monitor Grey-cheeked Thrushes in Illinois. Unfortunately, at that time, the transmitter could only send signals to a receiver, meaning you had to be near the bird to track its location. For Graber, this meant he was on a small plane, holding an antenna, attempting to locate a bird in the middle of the night over Lake Michigan. Bill later tracked another thrush for 930 miles to Manitoba, Canada, in the following years.
By 1970, Robert Fleming Jr., Tim, and Carol Inskipp were monitoring diurnal raptor migrations across different regions of Central Nepal. On November 2, 1976, Fleming Jr. recorded 305 Steppe Eagles within roughly an hour near the Dhampus ridge. On November 7, 1970, the Inskipps and their team documented a south-westerly flow of various raptors from the Daman area, including 174 Steppe eagles. The steppe eagle is one of the species that migrates from east to west, unlike the more common north-south migration seen in many bird species.
By 1984, the Argos satellite system was employed to monitor larger birds, including swans and eagles. Following the introduction of GPS systems for public use in the year 2000, research on bird migration gained momentum. In 2002, the largest citizen science initiative ever launched began. Called 'eBird,' it serves as a global database for bird observations. Individuals can record all the birds they have spotted or heard, making this information accessible to people around the world. At present, eBird has received more than 112 million checklists from 1.15 million users globally.
Grasping the behaviors and capabilities of birds during migration was still in its early stages when a Bar-tailed Godwit named E-7 set a new world record by flying 7,000 miles without stopping from Alaska to New Zealand. In 2022, B6, a four-month-old Bar-tailed Godwit, surpassed E-7's record by traveling 8,425 miles (13,560km) nonstop. A team of scientists initiated a project called "BirdCast" to monitor migrating birds, utilizing weather radar technology to forecast bird migrations.
Large groups of birds fly together, forming a massive cloud visible on weather radar. For many years, weather experts have considered these as just interference. However, BirdCast is now able to determine the type of birds, the quantity, and their flight direction by analyzing their movement and weather factors.
