Yala National Park in the southeast protects herds of elephant, deer, and peacocks. The Wilpattu National Park in the northwest, the largest national park, preserves the habitats of many water birds such as storks, pelicans, ibis, and spoonbills. The island has four biosphere reserves: Bundala, Hurulu Forest Reserve, the Kanneliya-Dediyagala-Nakiyadeniya, and Sinharaja. Sinharaja is home to 26 endemic birds and 20 rainforest species, including the elusive red-faced malkoha, the green-billed coucal and the Sri Lanka blue magpie. The untapped genetic potential of Sinharaja flora is enormous. Of the 211 woody trees and lianas within the reserve, 139 (66%) are endemic. The total vegetation density, including trees, shrubs, herbs, and seedlings, has been estimated at 240,000 individuals per hectare. The Minneriya National Park borders the Minneriya Tank, which is an important source of water for elephants inhabiting the surrounding forests. Dubbed "The Gathering", the congregation of elephants can be seen on the tank-bed in the late dry season (August to October) as the surrounding water sources steadily disappear. The park also encompasses a range of micro-habitats which include classic dry zone tropical monsoonal evergreen forest, thick stands of giant bamboo, hilly pastures (patanas), and grasslands (talawas).