World Migratory Bird Day 2013
Theme : Networking for migratory birds

N Munal Meitei *

Nganuthangong : winter visiting migratory birds :: pix - R.K. Birjit Singh

World Migratory Bird Day is observed on 11-12 May 2013. It was initiated in 2006 and is a global awareness-raising campaign highlighting the need for protecting the migratory birds and their habitats. On this occasion, people around the world take action and organise public events such as bird festivals, education programmes and birdwatching excursions to celebrate the Day and to help raise awareness about the specific theme.

This event also celebrates migratory birds in their region and the need for their conservation. This year's World Migratory Bird Day theme is "Networking for migratory birds." It seeks to highlight the importance of ecological networks and networks between organizations and individuals for the long-term conservation of migratory birds.

What are migratory birds?

Avian migration is a natural process, whereby different birds fly over distances for hundreds and thousands of km in order to find the best ecological conditions and habitats for feeding, breeding and raising their young. When the conditions at breeding sites become unfavourable due to low temperatures and some other reasons, migratory birds fly over to other regions where conditions are better. In contrast, birds that are non-migratory are said to be resident or Sedentary.

There are many different migration patterns. The majority of birds migrate from northern breeding areas in the summer, to southern wintering grounds. However, some birds breed in southern parts of Africa and migrate to northern wintering grounds, or horizontally, to enjoy the milder coastal climates in winter.

Other birds migrate in terms of altitude, moving higher up a mountain in summer, and residing on lowlands during the winter months. The primary physiological cues for migration are the changes in the day length. These changes are also related to hormonal changes in the birds. In the period before migration, many birds display higher activity or Zugunruhe (German: migratory restlessness) as well as physiological changes such as increased fat deposition.

The symbolic meaning of birds and their journey

Humans have always been fascinated and inspired by the phenomenon of bird migration. A dove, with an olive branch in its beak, returned to Noah's ark to announce the end of the deadly flood. Since then the dove has remained a symbol of peace and hope. In almost all cultures, flocks of birds have announced the arrival of spring for centuries, and the yearly rebirth of nature associated with it.

Migratory birds have the perfect morphology and physiology that enables them to fly fast and across long distances. During their migration some birds loses nearly half of its body weight. Migratory birds therefore rarely fly to their destination non-stop but interrupt their journey frequently to rest and feed, or to sit out a spell of bad weather.

Exactly how migrating birds find their flyways is not fully understood. Recent experiments indicate that they orientate along the Earth's magnetic field via special light receptors located in their eyes. The Bird's migration, its timing, response and shape are genetically controlled and appear to be a primitive trait.

Many, if not most, birds migrate in flocks. For larger birds, flying in flocks reduces the energy cost. Geese in a V-formation may conserve 12–20 % of the energy they would need to fly alone. Red Knots, Calidris canutus and Dunlins, Calidris alpina were found in radar studies to fly 5 km per hour faster in flocks than when they were flying alone.

Adaptations

Birds need to alter their metabolism in order to meet the demands of migration. The storage of energy through the accumulation of fat and the control of sleep in nocturnal migrants require special physiological adaptations. In addition, the feathers of a bird suffer from wear-and-tear and require to be molted.

The timing of this molt - usually once a year but sometimes two - varies with some species molting prior to moving to their winter grounds and others molting prior to returning to their breeding grounds. Apart from physiological adaptations, migration sometimes requires behavioral changes such as flying in flocks to reduce the energy used in migration or the risk of predation.

Long-Distance Migration

Many northern-breeding ducks, geese and swans such as Ruddy Shelduck (Nganu Thangong) of Manipur are long-distance migrants. Migratory routes and wintering grounds are traditional and learned by young during their first migration with their parents. For some species of waders, migration success depends on the availability of certain key food resources at stopover points along the migration route. This gives the migrants an opportunity to "refuel" for the next leg of the voyage.

Some Bar-tailed Godwits have the longest known non-stop flight of any migrant, flying 11,000 km from Alaska to their New Zealand non-breeding areas. Prior to migration, 55 percent of their bodyweight is stored fat to fuel this uninterrupted journey.

The Arctic Tern has the longest-distance migration of any bird, and sees more daylight than any other, moving from its Arctic breeding grounds to the Antarctic non-breeding areas for a journey of over 22,000 km.

How the Migratory Birds navigate?

Navigation is based on a variety of senses. Many birds have been shown to use a sun compass. Using the sun for direction involves the need for making compensation based on the time. Navigation has also been shown to be based on a combination of other abilities including the ability to detect magnetic fields (magnetoception), use visual landmarks as well as olfactory cues.

Migratory birds may use two electromagnetic tools to find their destinations: one that is entirely innate and another that relies on experience. A young bird on its first migration flies in the correct direction according to the Earth's magnetic field. It does this through a radical pair of mechanism whereby chemical reactions in special photo pigments sensitive to long wavelengths are affected by the magnetic field.

Large scale climatic changes, as have been experienced in the past, are expected to have an effect on the timing of migration. Studies have shown a variety of effects including timing changes in migration, breeding as well as population variations due to this present day greatest crisis.

Ecological effects

The migration of birds also aids the movement of other species, including those of ectoparasites such as ticks and lice, which in turn may carry micro-organisms including those of concern to human health. Considerable interest has been taken due to the global spread of the challenging avian influenza, H5N1, however migrant birds have not been found to be a special risk, with import of pet and domestic birds being a greater threat. Some viruses that are maintained in birds without lethal effects, such as the West Nile Virus may however be spread by migrating birds. Birds may also have a role in the dispersal of propagules of plants and plankton.

Threats and conservation Human activities have threatened many migratory bird species. Flying over long distances involves the crossing many international borders and entering different political areas with their own environmental politics, legislation and conservation measures. It is evident that international cooperation between governments, NGOs and other stakeholders is required along the entire flyway of a species in order to share knowledge and to coordinate conservation efforts. Hunting along the migratory route can also take a heavy toll.

The populations of Siberian Cranes that wintered in India declined due to hunting along the route, particularly in Afghanistan and Central Asia. Birds were last seen in their favourite wintering grounds in Keoladeo National Park in 2002. Indian subcontinent plays host to a number of migratory birds in summers as well as winters. It is estimated that over hundred species of migratory birds fly to India. The recent record of thousands of wintering bird's visit at the Wullar Lake in J & K was an example.

Needs for protection

Many bird species migrate in order to survive. However, migration is a perilous journey and involves a wide range of threats. Only a small number of birds are actually threatened by natural events. Sad but true, human activities are the source for most dangers migrating birds are exposed to. The loss of habitats due to pollution or exploitation caused by encroachment for settlement, agriculture, grazing etc. is the main threat to the migrating birds, as they are dependent on finding suitable breeding and wintering grounds as well as stopover sites along their flyways where they can rest and feed.

The loss of any of these sites used by the birds during their annual cycle could have a dramatic impact on the birds' chances of survival. Also, high-voltage power lines and wind turbines have a dramatic impact on birds, which are in danger of being killed by electrocution or collision. Poaching remains widely practiced in countries where people are highly dependent on biodiversity for their livelihoods. These are only a few examples and often a substantial decrease in population numbers within a species is the result of a combination of such factors. It is therefore hard to identify which individual factor poses the greatest threat.

In the recent census of the Water Birds in the Loktak Lake and its associated wetlands in Manipur, about 17 species of migratory birds were counted which is really a priceless asset of the State. But during the recent past, numerous trapping of these migratory birds are found in many of the common habitats. It is really a challenge to our society. Unluckily, it is also learnt that many birds are also killed on their way of migration to our state Manipur.

By spending crores of rupees, one cannot be able to call and bring back these migratory birds. Therefore, it is our duty of take care and conserves these Migratory birds. The way that the peoples of the Tangjeng Khunou in Thoubal district are doing is a stepping stone for safeguard of these migratory birds and otherwise we may not see these birds in our near future. The dream of the State for being an important Tourist spot will also be benefited by conserving and saving the migratory Birds coming to the State.