Arrival of migratory at Odisha's Chilika lake, the biggest waterfowl habitat in the country, has been delayed this year, a senior official said.
The avian guests generally reach the lagoon by the first week of October every year.
However, this year, they are yet to flock the lagoon or Nalaban, the bird sanctuary inside the lake, he said.
"At present, the sanctuary area is submerged, while the water level of the lake is high due to rain. Migratory birds may face difficulty in finding food in the inundated island. This might be one of the causes for their delay in arrival," said Divisional Forest Officer (DFO), Chilika Wildlife Division, Samrat Gowda.
The DFO, however, said some birds were seen hovering over the lake without landing on it.
"They might throng the lake once the water level recedes. We expect them to arrive in large numbers by the end of this month," he said.
Ornithologists and wildlife experts said the delay in the arrival of the birds was not due to the impact of cyclone Fani that hit the Odisha coast on May 3.
"Non-availability of food and incessant rain might have caused the delay," said former chief conservator of forests Sudhakar Mohapatra.
Food availability and favourable weather conditions are some of the factors that play a significant role in attracting migratory birds to Chilika, he added.
With the sighting of migratory birds on the shores of the lake and in the sky, the wildlife division has taken steps to protect the winged guests from poachers.
"We have set up 19 temporary camps in the lake and two mobile ones in the area to keep a vigil on the poachers," the DFO said.
A control room is also operating round-the-clock at the division office to monitor the poaching activities, he added.
Some 10,47,868 birds of 161 different species had thronged the lake last winter.
The migratory birds come to Chilika mostly from northern Eurasia, Caspian region, Siberia, Kazakhstan, Lake Baikal and other remote areas of Russia begin their homeward journey before the onset of summer.