SCIENTISTS at Delhi's Indian Agricultural Research Institute (IARI) have identified five wheat varieties developed in agricultural universities and institutes that are resistant to damage by birds, especially parrots. However, these varieties failed at pre-release trials and breeders are now trying to incorporate the bird- resistant property into other high-yielding wheat varieties, say ornithologist R K Bhatnagar and entomologist Vijai Shankar Singh.

Birds tend to damage crops from sowing to sprouting and from grain-setting to harvest. Parakeets are a particular nuisance, because unlike other birds that pick only on the grains, they prefer to carry the entire wheat cob to their nests. Of 14 parakeet species found in India, 10 cause "excessive depredation", says Bhatnagar.

"They bite off more than they can chew and the damage caused by them is greater (than that from other birds)," agrees Singh. In some cases, parakeets have destroyed upto 80 per cent of grain of the best known high-yielding variety of wheat, Kalyansona.

However, Singh and Bhatnagar found that some wheat varieties from Himachal Pradesh, Haryana, Delhi and Punjab were extremely "resistant" to the birds and lost only between 2 and 12 per cent of the grain. Close scrutiny of the structure of these bird-resistant varieties revealed that the plants had short peduncles - stems between the uppermost leaf and the wheat cob. The scientists postulate that the top leaf obstructs the bird in its attempt to get at the cob.

The length of these stems in the five bird-resistant varieties is between 4 cm. and 8 cm, compared to 15 cm in the Kalyansona. The scientists found that other varieties with large losses to parakeets also had longer peduncles.