Perching: letting birds control the pests in your field

Stand on the ridge of an aman rice field and look closely: here and there among the green stalks stand bamboo sticks or dry branches. On one sits a black drongo with its forked tail, on another a myna. Suddenly the drongo drops onto the crop, snatches a moth and flies straight back to its stick. That small scene is perching. A perch is just a place for a bird to sit, and perching is a natural, environmentally sound farming method in which sticks or pieces of bamboo are planted in the middle or along the edges of a field so that birds can sit on them and eat the insects that damage the crop. It costs almost nothing, yet it protects the crop and raises the yield, and across much of Bangladesh it has become one of the farmer's most familiar techniques.

There are insects in the rice field and hungry birds nearby, so why don't the birds eat the pests anyway? Because the open field gives them nowhere to sit. Drongos, mynas and egrets usually watch from a raised spot and then dive on their prey. In a wide paddy with no trees or posts, the birds stay in the trees at the edge and rarely venture into the middle. Perching fills that gap. Give a bird a seat inside the field and it sets up there, and the insects around it become its food.

One of the most damaging pests of rice is the stem borer. According to the Agricultural Information Service, three species attack rice in Bangladesh, the yellow, the dark-headed and the pink stem borer, with the yellow the most common. Its caterpillar bores into the stem and feeds inside. If it strikes during tillering, the central leaf dries and dies, a symptom called dead heart. If it strikes after the panicle emerges, the whole panicle turns white and empty, which is called white head. The moth flies at night and rests on the rice plants by day, and that is when birds spot it. The caterpillars of armyworms, leaf-cutters and leaf-folders are favourite food too.

The system comes together in a few steps. First, sticks or bamboo tips four to five feet long are driven into the ground at different points in the field, usually 10 to 15 metres apart. A light branch or crossbar is tied to the top so a bird can sit comfortably. Care is needed so the top of the stick is not hidden as the rice grows; agricultural specialists advise keeping the perch well above the height of the crop.

Then the birds take over. Sitting on the sticks, they catch and eat the caterpillars, stem borers and other harmful insects in the field. The need for chemical pesticide falls, and because less toxic chemical is used, the method is also safer for the environment.

Two kinds of perching are seen in the field. Dead perching uses bamboo canes, posts or dry branches pushed into the soil. Live perching means growing plants such as dhaincha, a tall green-manure crop, in the field, which grow up to become perches themselves. The purpose is the same: a place for birds to sit inside the field. Dhaincha brings an extra benefit. It is a legume whose roots capture nitrogen from the air, and it has long been grown in Bangladesh as a green manure. A few dhaincha plants on the ridges or in the field therefore do two jobs: they give birds a place to sit, and later, ploughed into the soil, they raise its fertility. The Department of Agricultural Extension encourages farmers to use both.

Each of the birds that come to the perches hunts in its own way, which is why together they make a good team. The best-known guard is the black drongo: glossy black, with a long forked tail and a habit of sitting on high points. The drongo is almost entirely an insect-eater. It sits, watches, sallies out to catch a flying moth or grasshopper and returns to the same spot. A stick in an open field is an ideal hunting post for it, and it is no accident that rural Bangladesh calls the drongo the farmer's friend.

The myna is less particular about food; it eats grain, fruit and insects alike. But it is an expert at walking through a field picking off grasshoppers, caterpillars and soil insects. The egret is a different kind of hunter again, stepping slowly through water or mud and seizing the insects, grasshoppers and small creatures that jump up at its feet. Anyone who has seen a line of egrets following a plough or a tractor knows how quickly they pounce on the insects turned up from the soil.

Between them, these three kinds of hunter put pressure on pests at three levels: above the crop, on the plants and near the base. The sticks bring them in, and the abundance of food keeps them there.

The first benefit is environmental. Pests are controlled without chemical pesticides, so there is less pollution of soil, water and air. The fish, snails, frogs and useful insects living in the paddy water survive too.

The second is cost. The method costs next to nothing: a few sticks or bamboo canes, which almost every village household has. The money for buying and spraying pesticide, and the labour for doing it, are saved.

The third is yield. With fewer pests, the plants stay healthy, dead hearts and white heads are fewer, and the harvest is larger.

The fourth benefit goes to the birds. Perching gives them food and helps keep the natural food chain intact, and birds in the field help protect biodiversity. A quiet bargain is struck between farmer and bird: the farmer provides the seat, the bird guards the crop.

Field experience supports the arithmetic. A November 2022 report in The Daily Star's Bangla edition described farmers in Patuakhali, where perching was in use on about 60 per cent of aman land. The report said a single bird eats at least 200 stem borers a day, and one farmer told the paper that where he used to spray pesticide three or four times a season, since perching he needed to spray only once.

Perching is a widely used technique, but it does not work the same way in every crop. Applying it well means understanding the crop and the land.

Rice is where it is used most, and it is especially effective against stem borers, armyworms and leaf-cutting pests. Perches go up in all three rice seasons, boro, aman and aus, and with the birds eating the pests, rice yields rise.

Vegetable fields benefit too. In bottle gourd, pumpkin, tomato and brinjal, perching reduces fruit borer and caterpillar attacks, so less chemical is needed and the vegetables stay in better condition. It also helps ease consumers' worries about pesticide residues on vegetables.

In pulses such as lentil, chickpea and mung bean, perching is used against pests and helps protect the grain, improving the quality of the harvest.

Oilseeds such as mustard, sunflower and sesame also use perches against harmful insects; damage to the flowers falls and yields rise.

In maize and wheat, perching is effective against leaf-boring insects and caterpillars, as birds on the sticks pick the pests off the crop.

Timing is critical. The sticks should go in as soon as pest attacks begin, before the crop suffers serious damage. Better still is to start early after transplanting, because that is when stem borer moths arrive to lay their eggs. Perches can stay in place from the early seedling stage right through to harvest. Once pest numbers have exploded, the birds alone struggle to keep up.

Perching is cheap and environmentally sound, and it takes little time or money to put in place. A little planning, though, makes the difference.

The first job is to observe the field. Identify which insects are damaging the crop and roughly how many there are, and plan how many sticks to put where, according to the size of the field and the crop.

The second is to gather sticks or bamboo, four to five feet long. Each one must be sturdy enough not to fall in wind or rain.

The third is to plant them, in the middle of the field and around it at even spacing, 10 to 15 metres apart. The larger the field, the more sticks it needs. A rough calculation helps. A bigha, the common local unit of 33 decimals, is about 1,338 square metres. With sticks every 15 metres such a plot needs about six; at 10-metre spacing, about thirteen. A single bundle of bamboo canes can guard a bigha of rice.

The fourth is to build the seat. Fix a light branch or crossbar to the top of each stick for the birds. Do not coat the sticks with tar or oil, which makes it hard for birds to perch.

The fifth is to attract the birds. Keep the field quiet and remove anything that could endanger them. Scattering a little of their favourite food, such as paddy or other grain, can bring more birds in at the start.

The sixth is to keep watch. Visit the field daily to see whether birds are using the perches. If they are not, try moving the sticks or adding more. If pest pressure is heavy, add sticks to strengthen the defence.

The seventh is to look after the field. Keep it clean and check regularly that the sticks are still standing. When pest attacks fall, the method is working.

The last job comes at harvest: pull the sticks up and store them somewhere dry to use again next season.

• Start perching before pest numbers build up.
• Never disturb the birds; they are your field's guards.
• Understand the part birds play in protecting nature, and treat them kindly.

Perching works best combined with other natural methods. The mechanical controls the Agricultural Information Service lists for stem borer include catching and killing moths with a sweep net, setting light traps to collect and destroy moths at night, and planting posts so birds can perch and eat the insects. Perching, in other words, is part of official advice. Using these methods together is what is called integrated pest management: nature's own tools first, and chemicals only when needed, as a last resort. Perching does not mean pesticide will never be needed; it means there is no need to spray poison again and again, needlessly, out of fear.

Understanding the stem borer's life cycle shows what else can be done alongside perching. The female moth lays her eggs in clusters near the tips of rice leaves, covered with a light brown coat of hairs. The caterpillars that hatch crawl down and bore into the stem, and once inside they are hard to reach. Integrated pest management therefore advises farmers to walk the field and pick off and destroy the egg masses by hand. Every egg mass destroyed before the caterpillars get into the stem means less damage.

When the moths are flying, birds and light traps come into play. By day, drongos and mynas catch moths resting on the rice; by night, moths drawn to light are caught in a light trap, which can be as basic as a bowl of water under a lamp. What falls into the trap, and how much, also shows whether pest pressure in the field is rising, so the trap serves both for control and for monitoring. Birds by day, light by night and the farmer's own eyes in between add up to a complete defence against the stem borer.

In the main rice-growing areas, such as Mymensingh, Sylhet, Cumilla and Jashore, perching is widely used. In the aman and boro seasons it is highly effective against stem borers and caterpillars, and with the birds eating the pests, the need for pesticides falls.

The north tells a striking tale in numbers. According to the national news agency BSS, in the 2025 boro season perching was planned on 468,428 hectares out of a target of 508,978 hectares in the five districts of the Rangpur agricultural region. In the aman season of the same year, BSS reported in November, perches stood on 369,160 of the region's 621,505 hectares. Earlier, in 2018, an agriculture official in Magura district told The Financial Express that all of the district's aman land had been brought under perching.

In vegetables, in growing areas such as Savar, Gazipur and Bogura, perching helps control fruit borers in bottle gourd, pumpkin, bitter gourd, tomato and brinjal, protecting quality and reducing pesticide use.

For oilseeds, it is used in the mustard fields of Pabna, Sirajganj and Faridpur. It helps control pests in the flowers of mustard and sunflower, and with pests under control yields rise noticeably.

In pulses, farmers in the Mymensingh and Rajshahi regions use it in lentil and mung fields against grain-boring pests, improving the quality of the crop and lowering production costs.

In wheat and maize, it is used in Rajshahi, Naogaon and Dinajpur: against leaf-boring pests in wheat and to reduce pest attacks in maize.

Orchards use perches as well. In Natore, Satkhira and Dinajpur they help reduce pest attacks in mango, papaya and banana plantations, and with birds keeping pests in check, fruit quality improves.

And in areas of Bangladesh where organic or natural farming is practised, perching plays an important part in chemical-free pest control and helps preserve the natural environment of the farmland.

Experience also shows the common mistakes. If the sticks are too short, the growing rice hides them and the birds stop coming. Sticks only along the ridges leave the middle of the field unguarded. Perches put up after an attack has peaked bring results too late. And spraying pesticide again and again beside the perches poisons the birds' food and drives them away. Perching rewards patience and routine.

Three lessons stand out from the country's experience with perching. It is environmentally sound: pests can be controlled without chemicals. It is cheap: it can be put in place at almost no cost. And it raises yields, because there are fewer harmful insects in the field.

Concern about the overuse of pesticides in Bangladesh goes back a long way. Spraying poison kills not only the pests but also useful creatures such as spiders and ladybird beetles, which themselves eat pests. The next attack is then worse, and the farmer is pushed to spray even more. Perching helps break that cycle. The natural balance that birds, spiders and useful insects build together in a field is, in the long run, the cheapest and safest protection there is.

The farmer's own health is at stake too. The person walking into the field with a sprayer on his back is the one closest to the poison. Spraying is often done without a mask or gloves, and drifting chemical is breathed in. Every spray that perching makes unnecessary is one less exposure for the farmer. That gain cannot be measured in money, but it is among the most important.

Perching is a modest, low-cost, environmentally sound technique that controls pests and raises output. For a farmer who wants to cut chemical pesticides and improve the quality of the crop, it is an excellent option. A few bamboo canes and a little attention bring drongos, mynas and egrets into the field, and under their watch the crop stays safe. There are few experiments in farming as cheap as planting a handful of sticks at the start of the season and watching who comes to sit on them.

Photo: Black drongos (Dicrurus macrocercus) in Bangladesh, R trisha / Wikimedia Commons (CC BY 4.0)