C.K Vishnudas
A Common Myna is seen to have brought food including insects, locusts, caterpillars, grasshoppers etc. 340 times in a day. A German ornithologist reported that single pair of Tits destroys, annually, at least 120 million insect eggs or 150000 caterpillars and pupae. The contribution of birds in controlling and managing insect pests in agricultural crops has not been recognized by farmers as well as agricultural scientists in general. Birds are good indicators of agro-biodiversity and an important group of life forms in any ecosystem. Though some of the birds are viewed as pest in certain crops especially in high external input agriculture, a majority is silently playing the most critical role of seed disbursers, insect controllers and rodent managers in and around our surroundings. Besides the beneficial birds, the de-predatory birds also play vital ecological functions in the ecosystems.
Traditionally, Indian farmers have been successfully evolving strategies to manage depredatory birds as well as attract beneficial birds into their farm. But these practices have been neglected in the course of modernization of agriculture. Farmers in general are returning back to more ecologically appropriate agriculture after the high external input and chemical agriculture started resulting in a decline in production. This new trend of “going back to nature”, also termed as organic agriculture or ecological agriculture is now being more widely acknowledged and appreciated by people all over.
Birds are part of biodiversity
Bird diversity in India is very high compared to other countries due to the diversity of natural habitats and landscapes. The one thousand four hundred species of birds seen in India contribute 15% of the total world species showing the importance of conservation. Also, according to Birdlife International, 12% of the word bird population is under the risk of extinction in the near future. Since birds have no boundaries such as protected areas or agricultural lands, their conservation activities should also look into the management of agricultural landscapes.
Birds and Pesticides
Application of toxic pesticides will also eliminate birds that entering into the agricultural fields. It has been reported that continued application of pesticides that contains heavy elements like cadmium and mercury in the paddy fields leads to the accumulation of these dreadful elements in the body of the birds through the intake of affected creatures like small fishes, shells etc. Use of Dichlophenol as an anti inflammatory drug in livestock has made the Indian white backed vulture Gyps bengalensis from a bird of sky to a bird of captivity during the past five years. When it come to birds of higher levels in the food chain, like raptors, owls and also egrets, it develops into different abnormalities like, laying of shell less eggs, some times, thinner eggshells. The eggs having thinner eggshell cannot be incubated by the birds. This inturn affects the reproductive capacity of the birds too.
Attracting useful birds into agricultural farms
Traditionally, birds were used as an effective pest management mechanism. For instance, in rice cultivation, farmers have the practice of keeping dried tree stumps in different localities in the field. Planting plantain along the ridges provided the necessary perching place for various species of birds. Birds such as Drongos, Mynas, Shrikes and Kingfishers used these perches to feed on insects and caterpillars from the rice fields during daytime. In the night different species of Owls use these perches to prey upon rodents that contribute to crop loss especially in food grain cultivation.
Another group of birds that play a vital role in rice fields are the Egrets, Herons, Water hen, Snipes etc. These birds feed on worms, moths and caterpillars as well as harmful soil organisms. A prior knowledge on bird ecology and systematics of the locality will help the farmers to adopt suitable bird attracting practices in their farms.
Some of the birds that render invaluable services in crops such as rice and other farmlands have been given in the box 1. This is based on field studies conducted by author mainly in Wayanad district of Kerala and not an exhaustive one.
Table 1: Beneficial birds of Rice crop
| No | Species name | Prey | Prefered feeding guild |
| 1 | Greater racket tailed Drongo(Dicrurus paradiseus) | Rice stem borer(Scirpophaga incertulas)Green horned caterpillar moth | Mostly rice field near to the woodland |
| 2 | Bronzed Drongo(Dicrurus aeneus) | Army worm (Spodoptera litura)Rice grass hoppers ( hieroglyphus banian)Green leaf hoper(nephotettix virescens)Brown plant hopper( Nilaparvata lugens) | Reach throughout rice field provided the perches are provided |
| 3 | Black Drongo(Dicrurus machrocercus) | Army worm (Spodoptera litura) | Reach throughout rice field provided the perches are provided |
| 4 | Rufous backed shrike(Lanius schach) | Leaf folder larva ( (Cnaphalocrocis medinalis)Case worm( Nymphula depunctalis)Green horned catterpillar(melantis ledaismene)Army worm (Spodoptera litura) | Prefers bushes around the rice fields, moves interior when perches are provided |
| 5 | White breasted king fisher(Halcyon smyrenensis) | Green horned caterpillar | Stream along the rice fields and uses perches provided |
| 6 | Little Egrette(Egretta garzetta ) | Green horned caterpillarLeaf folder larva | Scan entire rice fields feed on caterpillars , fishes and worms |
| 7 | Median Egrette(Mesophoyx intermedia) | Leaf folder larva | Scan entire rice fields feed on caterpillars , fishes and worms |
| 8 | Large Egrette(Casmerodius albus) | Leaf folder larva | Scan entire rice fields feed on caterpillars , fishes and worms |
| 9 | Cattlle Egrete( Bubulcus ibis) | Leaf folder larvaBrown plant hopper | Generally following cattle but feed on flies, insects and worms in rice fields |
| 10 | Pond heron(Ardeola grayii) | Brown plant hopperLeaf folder larva | Scan entire rice fields feed on caterpillars , fishes and worms |
| 11 | Purple heron (Ardea purpurea) | Green horned caterpillarLeaf folder larva | Scan entire rice fields feed on caterpillars , fishes and worms |
| 12 | Night heron (Nycticorax nycticorax) | Army worm, soil worms | Scan entire rice fields feed on caterpillars , fishes and worms |
| 13 | Chestnut bittern (Ixobrychus cinnamomeus) | Soil worms | A rare bird but seen foraging in rice fields |
| 14 | White breasted water hen (Amauronis phoenicurus) | Soil Worms and case worm | Scan rice fields and feed on worms. |
| 15 | Brown fish owl (Ketupa zeylonensis) | Rodents, fishes | Prey upon from the tall perches near rice fields and use perches inside the fields too |
| 16 | Ashy wren warbler(prinia socialis) | Rice ear head bug(Leptocorisa acuta) | Gleaning across stem and feed on bugs |
Mixed farm lands
There are good number of birds that feed on insects and various other creatures in farm lands. Among these, insectivores birds play a major role in managing the insect population in farm lands. Some of the birds such as oriental white-eye, sunbirds, Drongos, Flycatchers, Magpie Robin etc also help in pollination in various crops. Some studies shave shown that Crow pheasant (centropus sinensis) are very good in controlling red palm beetle, which is a critical pest in coconut palms.
Managing depredatory birds
Birds which damage crops resulting in an economic loss are generally termed as depredatory birds. These include some species of the granivorous(grain feeding) group of birds such as Parrots, Mynas, Munias, Doves, Sparrows etc. Crop loss due to grain consumption by these species are generally confined to two types of farm regions – areas where the seed sowing time differ considerably in different holdings and areas where food grain cultivation has been gradually decreased. Normally crop loss due to bird feeding of grains is negligible in India. However, crop loss will be higher in smaller areas of food grain cultivation as compared to large tracts. One of the study in rice field in Wayanad by the author shows that the economic loss due to crop damage and related financial loss by birds is indirectly proportional to the area under cultivation of the particular crop.
There are some species that cause damage on a wide scale. Economic threshold levels( ETL) for these species could be find out by closely monitoring the population size of birds in a given area that make damage. It has been recently observed by the author that birds such as white-breasted water hen started feeding on green banana that was cultivated in rice fields.
Conclusion
Location specific studies on feeding ecology, breeding biology, roosting ecology and population dynamics of different bird communities need to be conducted to make use of birds effectively for sustainable and eco-friendly agricultural production. Agricultural landscapes are the result of continues modification of natural habitats. Such farmlands also provide immense opportunities for studying the relationship between biodiversity and ecosystem services. Also changes in land use pattern and shift from food grains to other crops are resulting in the increased damage of crops by birds as a result of food shortage. Above all, the use of toxic pesticides in agriculture is emerging as the critical deciding factor for survival of many of the life forms. We should develop a farming method that allows all organisms to survive. This is possible through conservation and practising ecological agriculture.
C.K Vishnudas, Research Officer, RASTA, Kambalakkad P.O, Kalpetta, Wayanad. Kerala. www.rastaindia.org email : ckvishnudas@yahoo.co.uk
