the movement of elephants. Thattekad Bird Sanctuary, one of the important bird sanctuaries of India, is an evergreen low-land forest located between the branches of Periyar River. It has a rich and varied birdlife. Several species of birds, both forest birds as well as the water birds visit the sanctuary. Dr. Salim Ali, India's greatest ornithologist, once described this tiny, bird sanctuary, located about north-east of Kochi, as "The richest bird habitat in peninsular India". Periyar is one of the six major rivers flowing into the Vembanad lake. Vembanad Kol Wetland was included in the list of wetlands of international importance, as defined by the Ramsar Convention for the conservation and sustainable use of wetlands. It is home to more than 20,000 waterfowls—the third largest such population in India. Religious and cultural significance There are several places of religious significance along the banks of the Periyar. The famous Aluva Sivarathri festival is celebrated on the banks of the Periyar River in Aluva. The temple festival is conducted every year on Sivarathri day of the Kumbham month of Malayalam calendar. The Siva temple on the sand bank of Periyar River throngs with devotees every year on Mahasivarathri day. Kalady is a town located on the banks of the Periyar river. It is the birthplace of Sri Adi Shankara, the Hindu philosopher who consolidated the doctrine of Advaita Vedanta. Kalady started featuring in the spiritual map of India only after its rediscovery in the late 19th century by the then Shankaracharya of Sringeri and the subsequent consecration of a temple for Sri Adi Shankara in 1910. Located from Kochi, the Malayatoor Church is situated atop the high Malayatoor Hill. The church is dedicated to St. Thomas, who is believed to have prayed at this shrine. One of the most important Christian pilgrim centres in Kerala, this holy shrine attracts devotees in very large numbers not only from Kerala but also from the neighbouring states. This famous church is situated at Kurisumudi, a verdant hill in the Western Ghats girdled partially by the Periyar (river). The Church has a life-size statue of St. Thomas and the imprint of the feet of the Apostle on a rock. This shrine has now been accorded an international pilgrimage station. Environmental issues Pollution The lower reaches of the Periyar are heavily polluted. Industries in the Eloor industrial zone discharge waste into the river. Greenpeace India describes the