Bird populations in India dwindling at alarming rate
Who killed the birds?
Avian habitats face numerous threats
There has been a lot of change in the physical environment of our country in the past five decades, notes eminent ornithologist Zafar Futehally. "In the early 1950s, in our gardens in Andheri, Mumbai, there were jungle babblers (Turdoides striatus), magpie robins (Copsychus saularis), golden orioloes (Oriolus oriolus) and many more birds. Now there are nothing but crows in the same area," he rues.
Why are birds becoming fewer? The reasons are many and often complex. Habitat fragmentation and chemical contamination have proved hazardous for those that have a short range and also a short life span like Jerdon's courser (Rhinoptilus bitorquatus; see box Small range, greater threat). Other birds like the great Indian bustard which require specific habitats are threatened when their habitats get degraded (see graph Bird killers).
Lalita Vijayan of the Salim Ali Centre for Ornithology and Natural History (sacon), Coimbatore, notes that a study on wetlands conducted by her organisation revealed that "fish in wetlands had residues of heavy metals and pesticides, some at levels far above those prescribed by who."
The Indian skimmer (Rynchops albicollis), once common in the river systems of north India, is one bird whose habitat has become unsafe because of chemical contamination. It is categorised as vulnerable in iucn's Red List. "This bird's requirements overlap dangerously with those of people," says A R Rahmani of bnhs. Experts such as him say increased use of pesticides in cultivation of fruits like melons on the banks of large rivers is reducing the breeding sites for the skimmer.
In the Red List, the status of the falcated duck (Anas falcata) and black-tailed godwit (Limosa limosa) changed from 'least concerned' in 2002 to nearly threatened in 2006; that of the sociable lapwing (Vanellus gregarius) and the spoon-billed sandpiper (Eurynorhynchus pygmeus) changed from vulnerable in 2002 to critically endangered and endangered, respectively, in 2006. Significantly, all these are water birds.
The chemical bane doesn't just mean pesticides. Consider the case of the white-backed vulture (Gyps bengalensis). Decline in the bird's population was first documented in a breeding colony in Keoladeo Ghana National Park, Bharatpur, Rajasthan, by bnhs researchers in 1997. Numbers of breeding pairs in the park fell steadily through the late 1990s, and by 2000 there was none left. Later studies confirmed that the decline extended across northern and central India.
Surveys confirmed that the major ecological factors usually held as responsible for a population crash--food and nest site availability--were not an issue. But it was only in 2004, that a Nature (Vol 427, published online, January 28, 2004) study incriminated the anti-inflammatory drug, diclofenac--commonly administered to livestock whose carcasses are food for the vulture. There was much debate and conservation groups called for the immediate withdrawal of the drug from the market. The Indian government banned the drug in 2006.
A recent study published in the journal PLoS Biology (Vol 4, No 3, January 31, 2006) has proposed a substitute for diclofenac--meloxicam. When administered to vultures, it did not produce any visible negative effects. Experts, however, say the larger chemical problem remains unadressed.
Birds are not safe in other aquatic habitats either. The protected Chilika lake in Orissa, for example, is fast becoming a death trap for migratory birds. According to an estimate, in 2003 more than 200,000 birds fell to poaching. "Poaching is rampant in almost every part of the lake. The poachers very often use chemicals. The birds are sold in cities like Bhubaneswar," says Ram Behera, an anti-poaching activist.
In Asia, exploitation of birds for human use is the second most common threat to 50 per cent of all threatened species. About 70 per cent of these are consumed and 30 per cent end up in bird markets. Many fear that the bird trade threatens many more species, even those with wide ranges. There is documentary evidence of trafficking in 450 out of the 1,300-odd Indian bird species. The ones most traded are rose ringed parakeet (Psitttacula krameri), black-headed munia (Lonchura atricapilla) and rock pigeons (Columba livia).
Another threat is rivers getting flooded during breeding season nests in colonies on low sandbanks are destroyed. This is commonly attributed to deforestation in watersheds of major rivers and consequently rapid runoff. But another reason cannot be ruled out changing climate and consequent glacier retreat and change in monsoon patterns. "During a three-year study along Sikkim's Teesta valley, we found some birds had moved to altitudes higher than where they were found earlier," says Vijayan. "Other probable impacts of climate change can be found in the Andaman Islands. Here, sea level rise has affected coastal wetlands and the birds they host."
Exotic species render habitats (both grasslands and wetlands) unfit for birds. Water hyacinths are a major problem in wetlands and lakes. The growth of lantana around Dehradun district was one factor responsible for the disappearance of the Himalayan quail (Ophrysia superciliosa). Invasive species are particularly threatening for short-range species. For example, the domestic goat has affected regeneration of vegetation and imperilled nesting sites of the narcondam hornbill (Aceros narcondami) in the Andaman and Nicobar Islands.
But it's not only invasive plant and animal species. Non-native bird species have become invasive for many native bird species. The rock pigeon was introduced into many parts of the world, including India, from Europe for food and as game. These birds live in human habitations such as farmlands and buildings, and are known to transmit a variety of diseases to humans, domestic poultry and wildlife.
In the mid-19th century, house sparrows were introduced into the us from Europe to alleviate the homesickness of settlers from the old world. These adaptable birds spread their wings across North America and in many cases outcompeted native birds for nesting sites and resources. According to data collected by The Birdhouse Network--a citizen-science project initiated by Cornell University--in 2003, house sparrows account for 43 per cent of all species that take over nest boxes meant for native birds.
Similarly, the myna (Acridotheres tristis), which Indian farmers regard as a friend because it feeds on crop pests, is loathed as a pest in Australia.Introduced in the country in 1862 to control sugarcane pests, it destroyed fruits and grains, and aggressively competed with native wildlife species for nesting hollows.
No credible census
The ambiguity over the peafowl's status is symptomatic of a serious problem there is no formal nationwide survey to count birds like the Common Bird Census in the uk and the Breeding Bird Census in the us. Accounts of decline in bird numbers are mostly impressionistic. Of course, there are population estimates of some flagship species. But these are based on individual research studies which are usually region-specific. Some organisations like bnhs do conduct bird census in collaboration with international groups. Some of them, like the Asian Waterfowl Census (awc), enjoy a fair degree of credibility among professional and amateur birdwatchers. But similar programmes for terrestrial birds have not taken off.
In February this year, the forest department in Coimbatore did embark on a census along these lines.The two-day exercise involved amateur birdwatchers, botanists and wildlife photographers along with department personnel. But their objective was to prepare a checklist of birds rather than count the numbers of individuals of a species. Counts such as these end up being an inventory and do not detail how many individuals of a species survive. This is critical to know how many birds are threatened and the extent of the threat.
A review article by A J Urfi and his colleagues from the University of Delhi (Current Science, Vol 89, No 12, December 2005) notes that though there is general awareness of counting techniques, population estimates provided by most surveys are not reliable. "Population estimation exercises have been undertaken for a variety of endangered birds such as the Siberian crane (Grus leucogeranus), sarus crane, great Indian bustard, lesser florican (Sypheotides indica), Bengal florican (Houbaropsis bengalensis), narcondam hornbills and vultures. But some of these studies have not employed rigorous field methods," the paper says. There is more than a grain of truth in this contention. Surveys have rarely gone beyond impressionistic methods. For example, a 1998 survey to count water fowl in Keoladeo Ghana National Park claimed to use the 'total count' method. Actually what happened was that the surveyors went about counting birds around certain vantage points such as untarred roads and dykes. Similarly, another survey in Nanda Devi National Park, Uttaranchal, used the 'encounter rate and call index'--birds were counted when they were sighted.
The lack of a nationwide census means that we do not have data on the national bird, or even common birds like the house sparrow (see box Where have all the sparrows gone?). The disappearance of the house sparrow especially from urban areas is not something new, but so far there has been no response in India unlike the uk," says Ashish Pittie, editor of the journal Indian Birds.
Quite a few alarm bells rang in Europe when the population of sparrows declined drastically--by up to 85 per cent-- in London. The disappearance of sparrows in India has also been widely reported in the media, though reliable information on the sparrow population is still scarce. There is similar confusion over the status of another bird, the Indian shag (Phalacrocorax fuscicollis). It's usually deemed as a common bird. But only 627 individuals were counted during the 2005 awc from nine states.
"A dominant trend of bird-count exercises undertaken in India has been a focus on endangered birds, wetland birds, heronries and birds found in terrestrial habitats significant for conservation," claims the article by Urfi and his colleagues. "While the emphasis on endangered birds and high-value habitats is understandable, and also justified on account of their conservation significance, census of common birds has generally been ignored," the paper notes.
The failure to come up with credible bird counts has ecological ramifications. The loss of birds doesn't merely mean that our gardens are less redolent. Beyond aesthetics, birds perform crucial environmental services. Ecologists say that a region with a rich diversity of birds will also have a relatively high diversity of trees, shrubs, mammals, reptiles, frogs and invertebrates. This is why birds are recognised as 'indicator species' their presence indicates environmental health of an area. All the bustard species (great Indian bustard, lesser florican and Bengal florican) are indicators of the health of grassland ecosystems of Indian plains. The three species forage, shelter, display and breed in grasslands and their absence is the first warning signal that the grasslands are in peril.
"Birds also perform critical environmental services," says Ravi Shankaran of sacon. They are voracious eaters of weeds and farm rodents, they help keep insect populations under control, and pollinate and disseminate seeds. "So, extinction of bird species or their declining numbers disrupt ecosystem processes," says Shankaran.
For example, in many parts of the country, the decline of vultures has been accompanied by a rise in the numbers of carrion-eaters such as rats and feral dogs--animals that are reservoirs for diseases.
Another good example is the Keoladeo Ghana National Park. Rodents have, of late, become a scourge for residents of villages around the park, damaging crops. Experts such as Varma attribute the scourge to the decline in the numbers of birds of prey like the harrier.
The elusive crane
Keoladeo no longer gets its famous Siberian visitors
When it was declared a sanctuary in 1971, Keoladeo used to host more than 230 bird species. It was the celebrated winter home for the Siberian crane. The protected area no longer gets its most famous visitor. Cranes have not been sighted in Keoladeo since 2002. The black ibis (Pseudibis papillosa), a bird adapted to dry conditions, now dominates Keoladeo.
The reserve actually has a history that predates its notification as a sanctuary by more than 200 years ago. The Maharaja of the then princely state of Bharatpur, Suraj Mal, set the forest aside as a hunting reserve in the 18th century. The area had a natural depression and was named after a Keoladeo (Shiva) temple within its boundaries. The depression was flooded after the king ordered the construction of a bund at the confluence of two rivers, the Gambhir and Banganga.
Creating the sanctuary ironically led to a downslide in Keoladeo's fortunes.In 1982, a ban on grazing inside the park led to violent clashes between people living within its vicinity and park authorities. The ban also led to uncontrolled growth of vegetation, reducing the availability of water for birds. A long-term study by bnhs on Keoladeo's ecology has revealed that a ban on cattle grazing has led to weeds proliferating, blocking water channels.
At the same time, the Panchana dam on the Gambhir river prevented it from flowing into the park. The Banganga has long dried up. So Keoladeo, which earlier used to be flood-prone, is now dependent on rain. In late 2004, the Rajasthan government succumbed to pressure from farmers to prevent water from being diverted to the park. Water supply dropped from 15 million cubic metres to about half a million cubic metres.
Initially, a thick mat of water hyacinth festered in the Siberian crane's winter abode, preventing regeneration of other aquatic plants, which could serve as food for birds. Prosopis then took over.
When this reporter visited the park, groundwater was being pumped out. "The park is already on its deathbed and will be driven to extinction if nothing is done soon," says Harsh Vardhan, general secretary of the Tourism and Wildlife Society of India. Vijayan, however, does not want to give up. "We have recommended bringing in water to the park in a manner that benefits the whole region. Sustainable use of resources, for the benefit of surrounding villages, will ensure their support," she says.
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