The largest breeding colony of the Asian openbill storks is at Raiganj Wildlife Sanctuary, popularly known as Kulik Wildlife Sanctuary, in Uttar Dinajpur district of West Bengal. One of the eight species of the stork family, the openbill migrates for breeding every year to Raiganj in May and June. This species of the stork can also be seen in Bangladesh, Vietnam, Cambodia, China, Pakistan, Thailand, Sri Lanka and Nepal. Tarun K Roy, ecologist and environmentalist, who has done a survey of the breeding colonies for four consecutive years and compared it with officially recorded figures, found that after the breeding season Raiganj sanctuary had a population of 47,180 Asian openbill in 2011. In 2012, 2013 and 2014 it was 39,836, 44,298 and 46,842 respectively. 
The openbill also come for breeding to Nelapattu Bird Sanctuary in Andhra Pradesh, Danapur Military Cantonment in Bihar and Adina Deer Park in Malda but in less numbers.