The influx of the birds, who fly into the lake to avoid the intense winter and stay there for four to five months, had started on October 11 last, according to the state's Chief Wildlife Warden, SK Patnaik.

Since then, between 10,000 to 15,000 birds had landed in the picturesque Nalaban island, he said.

The arrival of the birds was delayed by about two weeks this time, Patnaik said indicating that the unprecedented heat and the phenomenon of global warming could be the cause of the delay.

But once the first flock of pochards, shovellers, gadwalls and ducks were spotted circling the Nalabana island on October 11, there had been no let up in the daily arrival.

The 15.5 sq Km nalabana island inside the lake, identified as a ``Ramsar Site'', attracted the largest number of migratory birds. A censusconducted last winter had found about two million birds in the sanctuary, he said.

Patnaik, who was here to discuss with the district administration regarding the Lakhary sanctuary on Monday last, however, pointed out that the water level of the Chilka was higher than last year following dredging of the mouth of the lake and the winding channel connecting it with the sea.

This had caused an increase in the salinity level of the lake water, he said adding ornithologists were studying the behaviour of the winged guests in the circumstances.

A survey conducted by the Chilka wildlife division revealed that the number of migratory birds, arriving in the lake had increased in the recent years. The number of bird species had also increased during the last four weeks.

Till now, Chilka, the country's largest waterfowl habitat, had witnessed the presence of as many as 167 species of bird species including the resident and migratory varieties.

According to the survey, while 84 species of birds were spottedinside the lake during 1994, their number had increased to over 100 last year.

A large number of flamingoes and pelicans, who come to Chilka to spend the winter and escape the biting cold of their native places, had chosen to stay back in the lake since the last two years.

Ornithologists were studying the behavioral change in these birds, who decided to make the lake their home.

The migratory birds, while traversing thousands of kilometres, also swooped down into irrigation reservoirs like Hirakud, Rengali and other waterbodies on their way.

A large number of birds even visited the Kumarkhunti minor irrigation reservoir located inside the Chandka wildlife sanctuary close to Bhubaneswar city.

Among the winged guests were the northern pintail, tufted duck, red-crested pochard, wigeon, common coot, purple swamphen, bartailed gadwit, little stint, tern, cormorant, teal, bar-headed Geese, flamingo, pelican and white ibis.

The rare birds spotted at Nalaban last year included smew duck, mallard, nakta,marbled teal and goliath heron. There was a substantial increase in the number of brahmini kites in the lake as well.

The increase in the number of brahmini kites had excited bird watchers as the specie was on a downswing in recent years allegedly due to increased use of pesticides in the crop lands and habitat loss, Patnaik said.

He said that the authorities had taken steps to improve the habitat, mainly in the Nalabana island, to ensure even bigger migration of the birds.