Officials of West Bengal's Forest Department fear that there may be a massive decline in the number of migratory birds coming to the Santragachi Lake in Howrah district this winter. “The preliminary estimates suggest that between 5,000 and 5,500 birds have come to the lake this season. However, the actual numbers can be determined only after a survey,” Divisional Forest Officer of Howrah Gautam Chakraborty told The Hindu on Wednesday. The lake, spread over about eight hectares, attracted 10,363 migratory birds of more than 20 species last winter. A survey is conducted in January, when the birds visiting the sanctuary are counted. The lake witnessed a sharp increase in birds' arrival until last winter. In 2008, about 2,500 birds were spotted. The next year it was nearly 6,000 and in 2010, it peaked to over 10,000. The lesser whistling duck is the most common visitor and it constitutes the largest chunk of the arrivals. Mr. Chakraborty said it was too early to speculate the reasons for the decline, as several factors could be involved. The Forest Department had failed to clear the huge quantities of hyacinth on the lake. Changing climatic conditions and warmer winters in the areas where the birds came from may have influenced the migration patterns, he added.