Perched on a steep rainforested hillside in the mountains near Lake Toba, Sumatra is a cluster of wooden bungalows with a majestic view across a misty tropical valley of an even higher mountain range, also clothed in jungle. From both sides of the valley the hooting of Siamang gibbons mixes with the mournful wailing of Lar gibbons, creating a bizarre ape cacophony. Add to this the growling and cackling of at least five species of hornbills, including the strangely beautiful Rhinoceros hornbill and Wreathed hornbill, spirit messengers from Heaven.