Thane Creek is part of the estuary

Estuary

An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....

 of the Ulhas River

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 in western India

India

India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

 opening into Mumbai Harbour

Mumbai Harbour

Mumbai Harbour , or Front Bay, is a natural deep-water harbor in the southern portion of the Ulhas River estuary. The narrower, northern part of the estuary is called Thane Creek. The harbor opens to the Arabian Sea to the south...

. It comprises the area stretching from Mumbra Retibunder to the Mankhurd-Vashi Bridge. It has been recognised as an Important Bird Area

Important Bird Area

An Important Bird Area is an area recognized as being globally important habitat for the conservation of bird populations. Currently there are about 10,000 IBAs worldwide. The program was developed and sites are identified by BirdLife International...

 by the Bombay Natural History Society

Bombay Natural History Society

The Bombay Natural History Society, founded on 15 September 1883, is one of the largest non-governmental organizations in India engaged in conservation and biodiversity research. It supports many research efforts through grants, and publishes the Journal of the Bombay Natural History Society. Many...

, as it is home to flamingoes and several other migratory and wading birds. The stretch of the Ulhas River

Ulhas River

The Ulhas River is a river of western India. It originates near Karjat in the Western Ghats Range, and flows westward through Raigad and Thane districts of Maharashtra between Kulgaon-Badlapur, north to Ulhasnagar and on to Kalyan, where it turns west to Thane...

 that turns north towards Vasai Creek

Vasai Creek

Vasai Creek is an estuarine creek, one of the two main distributaries of the Ulhas River in Maharashtra state of western India. The Ulhas splits at the northeast corner of Salsette Island into its two main distributaries, Vasai Creek and Thane Creek...

 is also mistakenly referred to as Thane Creek. Thane Creek was an important harbour in olden times, with the ports of Kopri

Kopri

Kopri, primarily a residential Colony, is situated on the eastern side of Thane Railway station, Maharashtra, India. The residences of IAS and senior officers as well as the High court and civil court Judges of Thane city and Thane district also lies in this area...

 and Kalyan served by it, though they have long been silted up. The city of Thane

Thane

Thane , is a city in Maharashtra, India, part of the Mumbai Metropolitan Region, northeastern suburb of Mumbai at the head of the Thane Creek. It is the administrative headquarters of Thane district. On 16 April 1853, G.I.P...

lies at the head of Thane Creek.