Maize

Bird Damage And Management

Introduction

• Crop damage occurs at various stages of crop production due to birds i.e. seeds may be removed after sowing, seedlings may be pulled out, grains in milky stage or at the ripening stage may be fed upon under uprooted conditions.
• Crop losses by birds are also known to vary in different seasons and in different regions and the management of birds require a clear understanding of the bird pests in various regions.

The major bird pests of this crop are

• Blue Rock Pigeons -Columbia livia
• Rose Ringed Parakeet- Psittacula krameri
• House crow- Corvus splendens.

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Nature Of Damage

• The pigeons and crows inflict the damage at the germination and seedling stages.
• The birds pick up the seed from the field after the post sowing irrigation and feed on the soaked seeds which were in the process of germination.
• They also pluck out on the developing young seedlings.

Bird damage

At the flowering stage, the Rose ringed parakeets infest the male inflorescence (Tassel) and feed on the anthers and pollen grains. At the tender cob stage, the parakeets damage the cobs with the silky style and green husk. At milky stage of the cob when they split and strip away the covering bracts thereby exposing the grain for easy feeding and further damage. This type of feeding is continued till the cobs reach dough stage. Damage by crows starts at this stage and they completely remove the spathes and eat the grains.

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Stages Of Maize Crop Vulnerable To Bird Damage

Stage	Species involved	Type of damage
Sown Seed	Pigeon and House crow	Disturbance of sown and soaked seeds and feeding on them.
Germinating Stage	House crow	Young seedlings are damaged. Aerial portion discarded feeding on the remaining food material present in the seed.
Cob emerging Stage	Rose ringed parakeet	Emerging tender cobs are damaged along with the silky style and green tender spathe (husk)
Milky stage	Roseringed parakeet	Green spathe (husk) are cut into pieces and the cobs are partially exposed and the grains are damaged by feeding on the milky contents.
Dough stage	Roseringed parakeet	The exposed tender grains are removed and fed
Mature stage	Roseringed parakeet,House crow	Green spathe dries up, and the husk is pulled out. The cobs are fully exposed. Grains are fed and causes total damage of the cob.

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Management

• Damages inflicted by harmful birds can be reduced using a variety of methods which can be categorised as lethal and non-lethal methods.

Lethal methods

• Lethal methods involve killing of birds, shooting, trapping, fumigation, poison baiting, egg and nest destruction, etc. In past, lethal methods were extensively used to control bird pests in India and elsewhere because killing was considered to be the surest way of getting rid of harmful birds.
• Killing of any bird species is now illegal in India and also not approved by the public.
• In view of the above facts, lethal methods of bird management are not recommended these days.

Non-lethal methods

• They do not involve killing of birds but instead aim at repelling them from their preferred crops fields.
• As a result of successful repelling, the damage gets distributed over larger areas and thus no longer remains an economic injury.
• If alternative foods of the concerned species are available, a part of the bird pressure may shift to such foods which would reduce the total damage to the preferred crop.
• Non-lethal methods include habitat manipulation, the use of repellents and provision of alternative food to pest bird species.

Habitat manipulation

• Bird damage is known to be higher in crops nearer to bird preferred habitats.
• Habitat manipulation involves removing roosting, nesting and feeding sites or food and shelter from the preferred habitats of harmful birds.
• The idea is to make these habitats less attractive for birds so that the damages to the adjoining crops may be reduced.

Repellents

• Substances and devices that cause pest species to avoid the otherwise attrative or palatable materials are called repellents.
• Bird repellents include several types viz., visual, auditory, Chemical plant-based and physical.

Visual repellents

• Visual repellents like scare crows have been used in India since ages.
• The most promising visual bird repellent known so far is the reflecting tape.
• It is a polypropylene metallic shining tape (11 mm wide, 0.025 mm thick, with one side red and the other silver) that reflects sunlight causing flashing effect and produces a humming noise in wind, thereby scaring birds.
• It is stretched between poles (with 2-4 twists per 30 m length and enough slack to allow undulation) 0.5 - 1.0 m above the crop, in parallel rows, keeping row to row distance at 3-5 meters.

Auditory repellents

• In India and several other countries, birds have been traditionally scared by producing noise orally, with fire-crackers or by beating drums and empty cans.
• Automatic acetylene exploders or bird-scaring guns that produce a loud exploding noise periodically have been used to scare birds in some parts of India.
• All noise producing devices have a major draw-back i.e. birds get used to them quickly.

Chemical repellents

• Many chemicals when used as seed dressings, sprays or dusts effectively repel birds from crops, thereby reducing bird damage.
• Seed treatments with Methiocarb [4(methylthio) 3,5-xylyl-N-methyl carbamate] has been found effective in reducing damage by weaver birds and sparrows to sprouting maize.
• Thiram (retramethylthiuram sulphide), a fungicide, protects sprouting maize from crows.

Alternative food

• Availability of alternative food is an important factor in determining bird damage to commercial crops.
• Generally, a scaring technique is more effective if alternative food is available to bird species being scared away.

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