Thane Creek is the estuary of the Ulhas river, opening into Bombay Harbour. It comprises the area stretching from Mumbra Retibunder to the Mankhurd-Vashi bridge. It has been recognised as an Important Bird Area by the Bombay Natural History Society, as it is home to flamingoes and several other migratory and wading birds. The stretch of the Ulhas river that turns north towards Vasai Creek is also mistakenly referred to as Thane Creek. Thane Creek was an importnat harbour in olden times, with the ports of Kopri and Kalyan served by it, though they have long been silted up.