Selective logging trucks reached Sinharaja's interior in 1971; by 1977 public protest had shut the sawmills down, and the haul roads cut for timber became the footpaths a Sinharaja forest day trip follows today. The reserve covers roughly 11,187 hectares of ridge and valley in the island's southwest wet zone, bounded by the Gin and Kalu river basins. UNESCO named it a Biosphere Reserve in 1978 and inscribed it as a World Heritage Site in 1988. The name translates as lion kingdom; in Sinhala the forest is still called Sinharaja Vanaantaraya. Lowland rainforest once ran unbroken across this quarter of Sri Lanka. Sinharaja is what remains: the largest viable block of primary wet-zone forest left on the island, and the most studied of Sri Lanka's rainforest landmarks. Dipterocarps dominate the canopy, with Hora trees rising past 40 metres and buttress roots spreading wider than a doorway. More than sixty percent of the tree species are endemic, and many occur in densities of fewer than ten mature individuals per hectare. Rainfall runs between 3,000 and 6,000 millimetres a year, so the leaf litter never fully dries and the mist along the Sinhagala ridge seldom lifts before mid-morning. Ornithologists have tracked the forest's mixed-species feeding flocks continuously since 1981, one of the longest unbroken studies of its kind anywhere. A single flock can hold forty birds of a dozen species moving as one unit, with the Sri Lanka blue magpie and the orange-billed babbler at its core. Nearly all of the island's endemic birds occur here — red-faced malkoha, green-billed coucal, Sri Lanka spurfowl, ashy-headed laughingthrush. Guided sinharaja forest day trip tours follow the same transects the researchers use, from the Kudawa gate on the northwest boundary toward Sinhagala peak at 742 metres. The reserve matters today for reasons that extend past its species lists. It works as a watershed for the southwest, feeding tributaries that irrigate paddy and tea land far downstream. Villages at Kudawa, Pitadeniya and Deniyaya supply the trackers and gate staff, and the mandatory guide fee carried inside the 2,700 LKR conservation charge pays those wages directly. Purple-faced langurs hold the mid-canopy; endemic agamid lizards and the Sri Lanka frogmouth keep to the understorey; torrent-breeding frogs occupy the streambeds. A sinharaja forest day trip tour amounts, in the end, to a walk through a working laboratory — a remnant measured, catalogued, and still yielding records that did not exist a decade ago.