At the Salim Ali Centre for Ornithology and Natural History’s International Conference on Indian Ornithology, I met scientists who picked up and discussed climate change and its impact on migratory birds.
Migratory behaviour of birds
Birds have long been used as indicators of environmental change. A global status report entitled “Bird Species and Climate Change” indicated that birds are “the quintessential ‘canaries in the coal mine’ when it comes to climate change.” The report assembles scientific evidence, which
demonstrates a “trend towards major bird extinction from global warming.”
Most species (84%) listed on the appendices of the Conservation of Migratory Species of Wild Animals (CMS) have the potential to be affected by climate change in some way.
About 53% from changes to water regime (droughts, lowered water tables, and so on),
24% from mismatches with food supplies, 18% from sea-level rise, 17% from habitat
shifts, 17% from changes in prey range, and 7% from increased storm frequency. These
are estimates based on expert opinion. The total proportion thought to be threatened
by climate change impacts is greater than that threatened from all other human-induced
When we study the migratory birds, the most important issue that emerges is the habitat quality. The birds need a coherent network of sites to facilitate their migratory journeys. Habitat quality is especially important on staging or stop-over sites, as during these times the birds need to consume large amounts of resources rapidly to continue their onward journey.
Such high quality sites may be crucial to allow migrants to cross large ecological barriers, such as oceans or deserts. The impacts of climate change can have disastrous effects on migratory species.
In the International Conference on Indian Ornithology (ICIO) 2011 held at the Salim Ali Centre for Ornithology and Natural History (SACON), Coimbatore, scientists discussed their preliminary studies on the migratory pattern of birds and how climate change was affecting India. Scientists, in their presentations, discussed how changes in temperature led to changes in reproduction patterns.
Beyond that, there was a range of expansion of birds towards the poles. This raises a gamut of issues for the migratory birds. They might not be able to find food. Even if they find food, they might not be able to find food at the right time.
There is a migratory restlessness in the birds and a great deal of mistiming in terms of food. As the birds travel from one place to another they need to protect themselves from the predators, need to
find the “right” kind of food during the journey because they need it to fly for long hours and survive through this migration journey.
One of the biggest threats to a significant number of migratory birds is the impact of warming on the polar regions. There is already evidence that a decrease in the melting of snow cover is leading to lack of land. This implies that the area available for the large populations of migratory birds that breed in these regions may shrink significantly and would eventually affect their numbers.
Says Dr Prakash Rao, Assistant Professor, Symbiosis International Institute of International Business, who has been doing research on climate change and its impact on migratory birds, “There were not many changes in the migratory pattern of birds till the 1900s. As a result of climate change, significant loss of key species has occurred. If the current rates of emissions continue, 15%–37% of the species could go extinct by 2050.”
In May 2008, an International Union for the Conservation of Nature (IUCN) assessment concluded that “climate change and even some attempts to tackle it are pushing one in eight species of birds
“There are direct and indirect losses due to climate change. Coastal birds like crane, storks, and birds of prey are at risk. The impact of climate change can be first noticed in the coastal
regions,” says Dr Rao. He further adds, “The impact in India is dependent on monsoon variability, crop production, melting of snow caps feeding the Ganges, erosion of coastal areas, sea level rise, agricultural ecosystems, erratic rainfall, and so on. Birds using these agricultural landscapes will be affected. Also, the long distance palaectic (includes the terrestrial eco-regions of
Europe, Asia north of the Himalayan foothills, northern Africa, and the northern and central parts of the Arabian Peninsula) migratory birds will see more danger.”
The Bird Species and Climate Change report brought out by WWF warns that extinction rates “could be as high as 38% in Europe, and 72% in north-eastern Australia, if global warming exceeds 2 ºC above pre-industrial levels (currently it is 0.8 ºC above pre-industrial levels).” Unfortunately, the current approach to bird conservation, which focuses on protecting specific
and limited areas containing high bird diversity will inevitably fail, simply because climate change will force birds to shift into unprotected zones as they desperately try to cope with an ever-warming planet and shifting habitats. In the US, bird populations have also shrunk, and nearly a third of the bird species living in the eastern Midwest and the Great Lakes areas could be lost.
In other parts of the world, the situation is just as precarious, if not worse. In North America, spring migration is occurring earlier and fall migration later in many species. For example, 25 migratory
bird species are arriving in Manitoba, Canada, earlier than they did 63 years ago.
As changes between seasons continue to become less clear, many birds are mistiming their migratory pattern. These shifts make them vulnerable to heat waves, droughts or cold snaps.
Of particular concern is the fact that some bird populations are abandoning their migrations altogether. For instance, cranes are starting to spend the winter in Germany rather than fly south to Spain or Portugal. Birds exhibiting this behaviour risk remaining in regions that can potentially be too cold for them to survive.
In such cases, a single severe winter event could decimate entire populations.
“Erratic rainfall could affect rain dependent birds like floricans and bustards in India,” explains Dr Rao.
Certain steps have been taken to track migratory birds and study their patterns.
One of them is the popular ringing method. Here, a metal band is affixed to the leg of the bird. Rings used are of negligible weight as compared to the bird’s body weight and the ring size varies according to the size of bird. Coloured plastic leg and neck bands are also used in large birds, such as geese. The leg on which the ring/ band is fitted also varies according to the year. The band is usually put on the left leg, if ringing is done during odd years (e.g. 2011, 2013, and so on), and on the right, if done during even years (2012, 2014, and so on). The ring recovery data is then obtained when the birds are re-sighted, recaptured, hunted, or found dead.
Colour marking is another tool, which 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. Also, temporary plumage dyes are often used on large waders to aid short-distance movement studies. Satellite tracking, transmitters, and radars are now increasingly being used to track the movement of migratory birds.
According to Dr Rao, “An assessment needs to be done in selected ornithological habitats. With strong empirical evidence and climate modelling data, we need to improve the data collection for these birds.”
Migrant Watch, an initiative by Dr Suhel Qader of the National Centre for Biological Sciences (NCBS) is a participatory approach to track the arrival of migratory birds in India. There are registered members of Migrant Watch who provide updated information on the sighting of migratory birds. The website lists the migratory birds that are being tracked. The members can upload the time and place of the sighting of the bird. They even have the option of uploading a picture of the bird. On the basis of the data generated from users, the arrival time of the bird is tracked. In this citizen-science initiative, people help scientists to generate a pool of data from
which the bird arrival can be tracked.
According to the Millennium Ecosystem Assessment, climate change is likely to become one of the most significant drivers of biodiversity loss by the end of the century. Biodiversity conservation can go a long way in offsetting the carbon emissions and reducing the negative effects of climate change. The conserved or restored habitats can remove carbon dioxide from the atmosphere, thus, helping to address the climate change issue by storing carbon. Moreover, conserving intact ecosystems like mangroves can help reduce the disastrous impacts of climate change, such as flooding and storm surges.
It becomes imperative that measures are taken to save the wildlife habitat, which in turn, would help in reducing carbon emissions, retaining the forest cover, and protecting many species from extinction.