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The Tonle Sap lake is a unique region formed by thousands of years of annual flooding from the Mekong River. During the rainy season, from mid-May to early October, the Mekong rises
and flows back into the Tonle Sap, reversing the river’s flow. During this period the Tonle Sap lake swells from approximately 2,500 square km to 10,000 square km. The lake level rises
in places from 2.2m to up to 10m. Almost a third of the country disappears under water.

The result is a daunting demonstration of Nature’s diversity and adaptability. Enormous forest trees stand half submerged in tannin-coloured water. Monkeys, snakes and insects “migrate”
to the upper canopy. Fish spawn in foliage which during the dry season provides home
to a symphony of birds.

After years of chaos, brutality and corrupt exploitation a semblance of normality appears
be returning to the Cambodian landscape.

Prek Toal is one of three core areas designated in 1997 by UNESCO as part of the Tonle Sap Biosphere Reserve. The conservation programme is run by the Prek Toal Environmental Station under the guidance of Frédéric Göes and supported by the New York based Wildlife Conservation Society, the French NGO Osmose and the Cambodian Ministry of Environment.

The single largest factor contributing to the destruction of the bird population is nest robbing
of chicks and eggs by local villagers. Twenty five villagers, including Oehn, are employed
by the station as wardens to protect nesting sites. It was Frederic’s idea to enlist the experience of former hunters and animal collectors to ensure maximum success in this venture.

In scientific jargon, the biotope around the Tonle Sap is known as “seasonally flooded fresh water swamp forest”. A few decades ago, this inundated forest covered 1 million hectares. Today, less than half remains. The waters contain the largest concentration of fresh-water fish
in the world and these in turn feed the last major colonies of water birds in South East Asia.

Numerous species of turtle, snakes and the Siamese crocodile are all on the Red List
of endangered species. Over a million water snakes are now thought to be collected each year and fed to hundreds of crocodiles in floating breeding pens.

129 bird species have been recorded in Prek Toal to date.

Among the rarest are:

Masked Finfoot 10 pairs  
Grey-headed Fish Eagle 15 pairs  
Oriental Darters 200 pairs Largest colony in Southeast Asia
Glossy Ibis 50 pairs Only known colony in Cambodia
Black-headed Ibis 200 pairs Largest colony in Southeast Asia
Spot-billed Pelican 700 pairs Possibly largest colony in the world
Milky Stork 10 pairs Only colony on mainland Southeast Asia
Painted Stork 1000 pairs Largest colony in Southeast Asia
Asian Openbill 1500 pairs Largest colony in Indochina
Lesser Adjutant Stork 40 pairs  
Greater Adjutant Stork 30 pairs Largest colony in Southeast Asia