Look up to the sky more often. Sky-traversing birds, especially when it is large in number, might be a sign they’re migrating from the northern hemisphere. Migrating is the greatest adventure in a bird’s life. The journey is arduous, considering huge risks await along the way: flying over ocean and across the deserts, with chances of being trapped in a storm or being preyed on by predators.
Many birds lost their lives before they managed to arrive at the tropical land they wished for, and more destinations due to competition with resident birds.
Migratory birds are capable of finding routes from one migratory location to another. This ability still amazes scientists to date, because no specific and accurate theory that can explain how birds navigate.
Birds' complex spatial memory is capable of creating memory maps of familiar locations—including relationships between locations—and distinctive landmarks and landscapes. This skill can also link the locations that have been visited, thus the safest flight route can be estimated.
To be able safely land on the destination, migrant birds cannot rely solely on direction orientation. In 1850, a bird scientist named Gustav Kramer discovered that birds possess a navigation ability similar to the sun compass. Using a compass and “clock” on its body, the migratory birds can reduce the risk of losing direction and predict the sun’s movement.
In contrast, night birds use stars as compass and self-orienting themselves on star rotations in the sky. The evidence on this matter was discovered by S.T. Emlen, an US zoologist. From the equator the stars appear to move fast, but they get slower near the pole.
There’s a spot exactly over the pole where stars would “stop”, which is called the rotation axis of the sky. In addition, flight orientation aids for the night birds are Earth's magnetism.
Research by the Institute of Zoology in Germany has proven through testing the behaviour of the Arctic Warbler and White-chested Babbler, which usually fly to southwest direction, under an artificial starry sky in the laboratory.
In the series of tests, both types of birds managed to direct precisely to the southwest when orienting themselves in the Earth's magnetic field. When the Earth's magnetic field was changed, they flew to the south.
The reliable ability of navigation then raises questions from experts on the location of the bird's “compass”. Biologists from Frankfurt, Germany, found tiny magnetic crystals on the upper skin near the beak of the carrier pigeon. They suspected the relation of these crystals to the performance of the brain as an orientation tool. However, the role of magnetic crystals as a bird's navigational tool has yet to be ascertained.
This bird compass doesn’t tell north and south, but pole direction and equator. Therefore, in order to know at what latitude they are, birds will mark the angle of inclination between the magnetic field lines and the earth's surface because this angle is closer to the equator than to the poles. Migratory birds use these three compasses as needed. The sun or star compass is used at the start of the journey, while magnetic compass is used to orient long distance trips.
So, how do they get back to where they came from? Some people believe that migratory birds store migration topographic maps in their brains. While others suspect birds are oriented to light, air pressure, or the smell of their environment.
Migratory birds
Anatidae, Scolopacidae, Accipitridae, Muscicapidae, Alcedinidae, and Sylviidae are among migratory bird families. Many bird species such as kites and warblers migrate to warm, insect-rich locations. They generally migrate at night relying on the moon and stars as a guide. During the day, kites use the sun to show direction.
Black-tailed Godwit, a species of Scolopacidae family
The ability of birds to travel long distances is similar to that of a seasoned sailor on an adventure in the ocean. Bird migratory activities are not only to find abundant food in the equator, but also self-defence for their survival and offspring.
They would travel thousands of miles to return to the north from their feeding ground for this reason. Migratory birds are formidable adventurers and uncompromising in their lives and destiny. Keep moving forward, never give up!
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Indonesia is one of the transit areas and destinations for various migratory birds from all over the world. Indonesia is the main migratory destination for eagles. This bird of prey flies through a route known as the East Asia Continental Flyway, which stretches from Siberia to Southeast Asia.
Estimated about one million raptors will traverse the Eastern Mainland Corridor which covers around seven thousand kilometres in length. One observing spot for raptor migration is Paragliding Hill in Puncak, Bogor, West Java.
We invite you to participate in migrating raptor observation on Saturday, October 28 2017 at 07.00 WIB at Paragliding Hill, Puncak, Bogor. Bring along your family or relatives to welcome these travellers from the north. Further information: (WA/LINE) 0811-11454-88