Vol 2 No 2
Dec 95

Bird Migration and the role of Sungei Buloh

Our Baby Tailorbird

Migratory Birds
Birds and other animals migrate because of changes in weather. Before the onset of winter, they move to where it is warmer and where there is food supply. Among all animals, birds have the longest migratory range. Migratory birds may fly thousands of kilometres to spend the winter in the south where it is warmer. Waders migrate from their breeding grounds in Siberia and northern Asian countries to warmer regions in Southeast Asia and the Southern Hemisphere. Waders are not the only birds that migrate. Other migratory birds include warblers, swifts, swallows and kites.

Finding the way

For those who have thought about the problems involved, navigation is the most mysterious aspect of migration. The vast distances involved and the tremendous feats of endurance performed by the birds only serve to underline this most wonderful part of the whole phenomenon—the fact that the birds are able to find their way on long-range flights often to return, year after year, to exactly the same breeding site.

The word "migration" is derived from the Latin "migrare" meaning to move from one place to another. Migration is the regular and usually annual movement of a population from a breeding area to a non-breeding area, and the return of most of these individuals to the breeding area.

There are many theories on how birds navigate. The Circadian Rhythms and the Celestial Navigation theory proposes an internal clock in a bird for full celestial navigation. Important navigational tools would include visual markers like landmarks or clues from taste, smell, light, dye or anything familiar emanating from a particular direction. Birds could also orientate with a fair degree of accuracy with reference to the direction of the sun, the stars and cues from the earth's magnetic field.

There are many paths, or flyways, taken by the majority of the migratory species. The route of migrating birds will often take them over areas totally inhospitable to the species. Land birds make long ocean crossings, water birds traverse the deserts and open country species fly over forests. In all cases the migrants are only likely to come to ground where they find a suitable habitat. This poses a problem for species which are site specific. These sites take on a very special significance and might, with some species, be so important that their loss could cause extinction of the species.
The East Asian Flyway
Waders are some of the longest distance migrants. Many species of waders previously considered to be exclusive birds of the coastal and estuarine mudflats achney rnigrate overland. It has since been realized that vast distances are covered overland and across open seas on each migration by many species of waders. Waders are so called because they frequent coastal mudflats, wading about in the nutrient-rich mudflats to feed during low tide.

For most long-distance migrants, the amount of reserves stored before migration is insufficient to allow them to make the entire flight without rebuilding reserves. Thus, migration must involve a wavelike alteration of migrating and feeding activity. Migrants make use of stopover sites like the ones found in the Park for refuelling before moving on again. Birds have evolved food gathering adaptations that enable them to feed on different types of organisms instead of depending on a particular species of organisms. Thus the Arctic wader that feeds on small worms in a sandy substrate is equally well equipped to feed in a muddy mangrove mudflat, like those found in the Park.

Survival Strategies
The storage of fat reserves under the skin is an important adaptation of the migrant. The capability of forming such reserves is critical to survival in a competitive environment.

Territorial behaviour is another way in which the birds increase their chances of survival at stopover sites. Birds defend their territory against other birds of the same species to minimise competition for the limited food supply available.

Individuals of most species of transients migrate at night to avoid air turbulence caused as the sun heats the earth's atmosphere, and perhaps to minimise threat of predation. Transients are birds that stop over at a location before moving on again.

Migratory birds also fly in certain formations. One of them is the well known "V" formation. The aerodynamics of flying in this formation results in less energy spent during flight.

Sungei Buloh Nature Park
The Sungei Buloh Nature Park is situated along a major migratory route, the East Asian Flyway. During the migratory season from September to March each year, migrants stop over at the Park before moving on with their journey. Waders like the Redshanks, Whimbrels and Plovers can be seen in hundreds, sometimes thousands, on the mudflats. Other birds like the reed-warblers, kingfishers and bee-eaters are also common migrants, among the trees and shrubs surrounding the ponds. Our unique mangroves, mudflats and freshwater habitats provide suitable conditions for both waders, passerines and other birds to feed and roost, and rare opportunities for visitors to enjoy the flight antics and sights of these feathered visitors from afar.



© Sungei Buloh Nature Park




Vol 2 No 2
Dec 95

Bird Migration and the role of Sungei Buloh

Our Baby Tailorbird Baby Tailorbird

Our "Baby", as we would call it, was found alone on the ground in the Park in a damaged nest after a storm. Baby was too weak to even open its mouth when we first had it. Chicken pellets, mixed with vitamins and water, were fed to the bird with a stick. Baby survived, and soon became a feeding machine! The mouth, with the clearly evident gap, was all we could see with its constant chirp for food. The bird would only excrete after being fed, naturally while the mother should be around to clean up the nest. The excreta would come neatly in a bag which could be easily picked up and thrown away so it does not soil the nest—the wonder of nature!

After a week, it weighed about 10g. The feathers were fully out of the follicles and it could walk around the nest.

Baby, as it turned out to be, is a Common Tailorbird. When it grew too big for its tiny nest, it was ringed (identification band around the leg) and put in a 2m x lm x lm cage so that it could learn to fly while kept safe from predation. After a month, it was released. For a while, Baby could be seen around the cage pecking at the worms we left for him. Soon, it stopped hovering around and would disappear for the most part of the day. After about 5 weeks, Baby did not return again. We were glad for its freedom and hope it would one day come back to visit,... with its family!

For more about Common Tailorbird (Vol 6 No 3, Dec 99)



© Sungei Buloh Nature Park