Migration is the regular, recurrent, cyclical seasonal movement of populations from one geographic location to another. It is marked by the eventual return to the original place of departure. Migration is most evident among birds that usually follow a yearly cycle of migration. In some cases this migration is obvious and involves huge distances but at other times it is much more subtle. Birds migrate for many reasons that include the need to travel to
areas where food resources are at their peak abundance, the climate is milder and there is less competition for safe nesting places. But the main environmental trigger for bird migration seems to be the changing ratio of daylight and darkness. With the onset of winter, days get shorter reducing activity hours. This triggers the almost entirely instinctive phenomenon of bird migration. Not only is bird migration an intriguing phenomenon for those who wish to know the source and
destination of these birds, the study of bird migration itself is significant for humans in many ways. Migration has considerable ecological significance. It enables birds to exploit peaks of food production and to settle in areas where they could otherwise not live. The study of migration is important for our understanding of global climate change phenomenon, spread of avian diseases and areas important for conservation. Additionally, all birds have recreational value as
birdwatching and other forms of nature related activities become increasing popular.
Study of Migration
The study of migration has been through marking of birds, field observations, and advanced studies like radar and satellite observations. Migration research is constantly changing, and new methods are emerging all the time. Historically, migration was tracked through ringing studies. Bird ringing (also known as bird banding) is a research method used to acquire accurate information about bird movement and life span. It consists of catching birds and
attaching a small individually numbered metal or plastic ring to their legs or wings; if it is found later the bird can be identified by this number
Migration Study Tools
Metal bands/rings: The original tool, this technique involves affixing an inscribed metal ring to the left tarsus (leg) of a bird containing an unique serial number on the outside and an address where recovered bands can be sent on the inside. Ring-recovery data is obtained when ringed birds are resighted, recaptured, hunted, or found dead.
Colour marking: This modern tool uses bright colour marks that enables observation of the bird from a distance through a telescope or binoculars without the need to capture/shoot the birds. The unique combination of colours and marks allows for identification of individuals or marking locations.
Plumage dyes: Temporary plumage dyes are often used on large waders to aid short-distance movement studies.
Transmitters/Radars: Sophisticated electronic devices that can beam information on the movement of birds are being increasingly brought into use.
Use of Colour Flags
The use of colour flags has transformed our understanding of the migration routes and identifying major staging areas of shorebirds. Coloured neckbands with alphanumeric engravings are also being widely used to tag waterfowl like swan and geese. Colour flags are coloured plastic rings that are shaped so that a tab extends from the ring providing a much larger viewable surface area than conventional colour rings. In 2004, a trial using alphanumeric
engraved colour flags was undertaken in Australia with a high degree of success. This system is now used increasingly throughout the East Asian-Australasian Flyway with very rewarding results, especially with the advent of digital cameras and "digiscoping" enabling photographs to be taken of flagged birds. Additionally, many bird-watchers, armed with binoculars or a spotting scope, are now able to see the various combinations of colour flags that help to establish the
locality where the birds were originally marked. The reporting rate from flags has far outstripped the recovery rate from conventional ringing. Each country or region in the East Asian-Australasian Flyway uses a unique colour combination to establish where the bird was flagged. The position of the metal band is not required to determine the flagging location. For two colour flag combinations the flag position sometimes varies with both flags often placed above the joint in large
waders and a one above and one below the joint in the case of smaller waders. Engraved numbers and/or letters are used on many of the new flags. These help identify the date and place where the bird was flagged. Some example of flags in use in the East Asian-Australasian Flyway can be found at
Sadly, there is no global register or system of colour marking of waterbirds, although there are well coordinated schemes for Eurasia/Africa through EURING and AFRING. In the Asia-Pacific region, colour coordinated schemes are limited to few species/species groups in some flyways. The most advanced and coordinated programme in our region is run by the Australasian Wader Study Group who monitor five million shorebirds on the East Asian-Australasian
Flyway. They have a well-documented system of reporting sightings and these are mentioned below. In India, the most actively used migration corridor is the "Central Asian-South Asian Flyway". Unfortunately, the Central Asian Flyway Action Plan has been unable to establish any meaningful framework to promote coordinated approach to bird banding activities and there is no accepted system or procedure in place to facilitate systematic observation or reporting. Bombay Natural
History Society (BNHS) has been tagging migratory birds with metal rings since 1959 and are the only accredited ringers in India. Birds ringed in India have a poor recovery rate of less than 1%. Over 400,000 birds have been ringed by BNHS till 2002.
Birds that migrate from the same geographic region often follow broadly well-defined routes known as migratory flyways. There are eight recognized shorebird flyways around the world. The Asia-Pacific region, as defined by the main migratory routes of waterbirds, is made up of three shorebird flyways - the Central Asian Flyway, the East Asian-Australasian Flyway and the Western (or Central) Pacific Flyway crossing 57 countries and territories in
the region. The East Asian-Australasian Flyway, is the best studied and stretches from Siberia and Alaska southwards through east and south-east Asia to Australia and New Zealand, and supports over five million migratory shorebirds. The Central Asian flyway spans about 30 countries from the Arctic to the Indian Ocean. But these flyways are just generalizations and bird populations have been known not to strictly follow it. During migration, birds depend on strategically located
staging areas where they stop to rest and "refuel", by building up fat deposits, before continuing their migration.
What to do when you find a tagged bird in India?
Anyone who spots a shorebird with a flag or other color markings, should please forward the following information:
1. Name and contact address of observer(s):
3. Location (with latitude and longitude if available):
4. Kinds of band(s) (metal ring/ flag/colored ring):
5. Color and number of color band if observed:
6. Position of bands:
Right or left leg:
Above the joint (type of marker / color):
Below the joint (type of marker / color):
7. Date and time of observation:
8. Number of birds of the same species spotted:
9. Photo, if available, attached:
The above information can be sent or shared at:
1. Report the observation with any images obtained to Dr. S. Balachandran, Senior Scientist email@example.com. BNHS maintains Indian ring recovery records and is the Key Banding Scheme Contact for India.
2. Wetlands International has developed a website to promote sharing of information on colour marking and satellite tracking of waterbirds. These
pages contain the key contacts for birds tagged in the Asia-Pacific region. Additional tagging programme details are found
3. For birds tagged in the East Asian-Australasian Flyway, reports can be sent to Clive Minton at firstname.lastname@example.org in case you cannot establish country of origin from lists such as are available at
Asia-Pacific Shorebird Network
4. Send a mail to us at:
email@example.com - we will use our experience to help track down your bird.
Suggested reading and references:
Migration of Birds by USGS