By JOHN ARUGA
DO YOU know that Papua New Guinea plays host to millions of international travelers every year? These international travelers do not need visas or transit permits, a cumbersome process which many of us nowadays complain about. They do not need such travel endorsement even though each year they travel through about 12 different countries including Papua New Guinea.
These travelers are shorebirds. They travel 100,000 km each year, stopping over many countries across the Asia and the Pacific to winter over in Australia and New Zealand every year between October and December.
Papua New Guinea and countries in Asia play host to these avian international travelers by providing “fuelling stations” or wetlands.
The extensive mudflats of the Gulf of Papua, the freshwater wetlands of the Western province and other wetlands in the country provide much needed “fuelling stations” for these shorebirds. Those who live near extensive shorelines, may notice on occasions the shoreline literally packed with hundreds of birds. They persist for over a month or so and they are gone! For almost a year, the shoreline is clear then suddenly they appear from nowhere about the same time. These are shorebirds migrating from the cold, harsh winters of the northern hemisphere in the Siberian and Russian tundras to the warmer winters of the southern hemisphere in Australia and New Zealand. These birds may fly stretches of over 8,000km without landing.
The greater sand plovers are born and raised in a central Asian desert; the grey-tailed tattlers and Terek sandpipers in a far eastern Russian riverbed; the great knots on a mountain tundra slope in the north of Russia; the eastern curlews on central Asian grasslands; the Asian gotwitchers, black-tailed godwits and broad-billed sandpipers in a Siberian bog; and the ruddy turnstones on an area of tundra overlooking the Arctic Ocean. On a worldwide scale, ten of these migration routes are recognized and cover large expanses of land in Europe, Africa, Asia and Americas. These migration routes are called flyways. One of the flyway that is of interest to us is the East Asian-Austrasian flyway.
How does the cycle start? Let us take the red knot for example. The cycle for the little red knot may start in June -July when there is northern summer, where they breed in northern Asia. They build their nests, lay eggs and raise their young during the short arctic and boreal summer while the day lengths are long and food is abundant. They occur in low densities across the vast tundra, forest and steppe zones of north-eastern and north-central Asia, in habitats which bear little resemblance to their wetland non-breeding habitats.
Life is busy during the northern summer from mid-June to late July. The red knots have just under four weeks to court, mate, and lay a clutch of four eggs and complete incubation, and then another three weeks to raise the chicks to a stage where they can fly. Competition for the best breeding territories and best mates is fierce. And these activities are heralded by their intense songs and courtship display flights. However, after about a week, successful birds pair up and egg laying starts; one egg per day for four days. As in other shorebirds, eggs are incubated for 20-21 days. During incubation, male and female red knots share the brooding, relieving each other every 17 hours or so. This ensures that there is parental movement at the nest once or twice a day, reducing the likelihood of any predation by Arctic foxes and other predators.
When the eggs hatch, the females abandon the scene leaving the chick-care entirely to the male. The female group together and spend hours feeding on spiders and craneflies to fuel up for the flight south. And they are off again, making a similar trip south, along a similar route (flyway) arriving in Australia sometime in September.
In the meantime, each male takes sole responsibility for his chicks. Although the chicks can feed themselves, caring for them is still a lot of work. With peak temperatures of 50C, it is pretty cold and the chicks lose body heat as they forage in the open expanse of the tundra. Every so often, they need to be warmed up to be able to continue foraging. They accomplish this by huddling together under their father and pressing their necks (which have special thick blood vessels) against the area of bare warm skin (the brood patches) on their flanks. The father shivers and pumps his own heat into his offspring.
It is also during this time that the fathers teach the young chick about survival strategies and skills. The male teach the chicks about dangerous predators. The skuas that roam the tundra at this time are particularly dangerous. When the skua approaches, the father calls out and the chicks freeze. Without movement, even the skuas have difficulty finding them on the tundra. After a week, the chicks can maintain their own body temperature without adult assistance. After two to three weeks, males call it quits and take off towards the south themselves, leaving the chicks to fend for themselves. The young chicks fend for themselves and after they complete fuelling, they find their way south alone, assisted only by their inbuilt navigational programs.
After breeding, in the highland arctic tundras of eastern Siberia, Great knot, sandpiper migrates southwards to the coast of the Korean peninsula and north-eastern China. Here flocks spend several weeks feeding and they accumulate large reserves of fat just under the skin and around the internal organs. Just before the southward migration, this fat may represent as much as 50% of the body weight. This fat is burned up in only three or four days as they fly south non-stop for up to 6,000km across the vast expanse of the south-western Pacific ocean to Australia for the non-breeding months. Some of these birds ‘stop over’ in Papua New Guinea for ‘refuelling’ before heading south to Australia.
During their non-breeding winter in Australia and New Zealand, they rely on foods from the mudflats and wetlands. The non-breeding winter for these shorebirds may last from September to late February and early May. During this period , they need to store enough fuel to last several days for the long flight up north to its breeding grounds. When, we humans exert ourselves, our bodies process sugars, which are turned into work and heat. But sugars can only be stored in the liver, and will be exhausted within minutes once the birds are under way! The best source of energy for flights of long duration for these birds is fat., a fuel that humans are not able to use in unmodified form. But, birds can, and fat can be stored in a pure form. The metabolism (burning) of fats yields as much as eight times the energy that comes from the combustion of the same mass of muscle tissue, the only alternative fuel. Thus, fat is the fuel of long distance ,globe trotters such as the shorebirds. The knots and godwits and tattlers and sandpipers store masses of it. In preparation for their long flight back north, the shorebirds store fat in the subcutaneous layers and in the last week before the flight they fill the abdominal cavity. The abdominal cavity has the advantage that the circumstance, and therefore the drag of the body in mid-air does not increase further. This saves on flight costs. Another way to fly a greater distance, per gram of fat stored, is to reduce the size and mass of body organs that are not really necessary during the flight. In other words, getting rid of what we ,humans dread most about during travels -excess weight (baggage)! How do shorebirds reduce their excess baggage?
In preparation for take off, large digestive organs including the liver shrink and they are reduced to the smallest size that will be appropriate for survival when they reach their Asian destination. This saves on the mass of the structure that needs to be carried in flight. As the large digestive organs shrink, there is a proportional increase in the flight muscles. As departure approaches, flight muscles increase in size. The birds gets lighter during the migration as fat is burned.

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