Science & Medicine:Natural Sciences
Trouble from the sky
Birds are a delight to watch and to listen to. But sometimes they can also be harmful if not controlled. Birds feeding on ripening grain, such as the red-billed quelea, are known to be very damaging to rice and in Africa small farmers have few options to manage them.
Traditionally, women, along with their children, run up and down in the field, shouting, waving, clapping hands, throwing stones, and sometimes trying to scare the birds off with rattles and drums. Children often miss school as they are busy chasing birds off their parents’ rice farms
Farmers in Senegal and Mali attribute 10–15% crop loss to birds. Annual surveys over several years in the Senegal River Valley, a key rice belt in West Africa, show that farmers consider weeds and birds as the two most important pests in irrigated rice production.
The CGIAR research program on rice called GRiSP identifies birds as the second most important biotic constraint in African rice production after weeds, based on farmer surveys in 20 African countries.
However, there are limited recent and accurate estimates of the rice crop losses inflicted by birds, according to Dr Matty Demont, AfricaRice economist.
Since bird inflicted losses are a major obstacle to the development of intensive rice production in the Senegal River Valley, Dr. Demont tried to estimate the losses.
His study indicated that birds cause more than US$9 million in losses in the Senegal River Valley per year, with an annual bird damage of 13.2% of potential rice yield during the wet seasons from 2003 to 2007. The study also indicated that losses reach $18.6 million when pressure from birds is highest.
Moreover, farmers indicated that, at high bird pressure, traditional birdscaring methods are not effective. His study suggests that monitoring, controlling bird populations by applying avicides on a large scale, and insurance measures against massive invasions are urgent.
In an AfricaRice survey near Saint Louis, Senegal, farmers said that, if they managed their weeds in their rice fields, they would have fewer bird attacks. AfricaRice weed scientist Dr. Jonne Rodenburg found out that the farmers were right.
His experiments showed that weed free fields discouraged birds. Weedy fields attracted birds because they fed on weed seeds, found shelter in the weeds, and perched on the weeds to eat the rice.
In general, birds can be kept away from rice fields by following good agricultural practices. In addition to keeping fields weed-free, planting early maturing rice varieties, experimenting with different planting dates, and avoiding open water in the middle of rice fields are recommended to farmers.
Also, the removal of nesting, perching, and roosting sites around the field can reduce the number of birds. Reflective ribbons or used video/cassette tapes and nets have been found to be effective, too. In some places, farmers use large nets to catch birds or sound cannons and scarecrows.
However, birds quickly get used to such methods. Therefore, farmers are advised to combine the techniques. Sometimes broad spectrum poisons are used to kill destructive birds. However, aside from damaging the environment and human health, these also kill birds that do not eat grain.
Alternatives to these harmful pesticides, such as bio repellents for birds, are now increasingly being promoted across many countries in Africa. In addition, scientists are continuously working with farmers to help develop earth-friendly tools to protect rice crops from birds.
However, Dr. Demont points out that, if one farmer scares birds from his field, these birds only move to adjacent fields. His study recommends that policymakers treat regional bird control as a public good towards increasing domestic rice production as well as ensuring that children go to school instead of chasing birds.
For more information, visit www.AfricaRice.org
Podcast credit : Savitri Mohapatra, R.Raman, AfricaRice
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