The Edible Nest Swiftlets of Borneo
Sarawak, one of the two Borneo States of Malaysia, is a picturesque land of hills and twisting river valleys. Historically, most of the lowlands were vegetated by evergreen tropical rainforest.. Longhouses were scattered along the banks of rivers as far as they were navigable by boat, and, in places, beyond. Rising occasionally out of this rich network of waterways and tropical rainforest are blocks of karst limestone, some isolated and others gathered into small mountain ranges.
All these limestone outcrops were formed as reefs under geologically ancient seas. From this origin, many are penetrated by hidden subterranean channels and caverns. Some of these cave systems are huge, extending for kilometres, encompassing thousands of cubic metres.
Where these underground chambers are isolated from the outdoor air and light, strange cave fauna have evolved living deep inside the mountains. Where the rivers and caverns are open to the surrounding forest, an on-land equivalent to an inter-tidal zone develops, with populations of bats and specialised cave-dwellng birds, the swiftlets, migrating in and out of the cave mouths each day or night to feed – whilst leafy plants and, deeper inside, grey-green algae, thirst for life-giving daylight.
Over the past few decades, much of the lowland forest has been cleared to make way for oil palm plantations, new urban settlements and roads. In this altered, but still green environment the outcrops of limestone have become refugia for wildlife. And the caves within have become tourist destinations, attracting many thousands of visitors wanting to witness their huge scale and unusual fauna – in particular the great tides of bats and swiftlets that flow in and out at dawn and dusk.
Of these, the edible nest swiftlets (Aerodramus species) are famous for their highly sought after and prized cup-shaped nests fashioned from dried saliva. Worth thousands of dollars per kilo once cleaned and dried, the demand for nests has led to many populations of edible nest swiftlets being cropped almost to oblivion – – as observed by the writer Edward Posnett in his book Harvest.
One of the largest colonies of swiftlets in Sarawak inhabited the Great Cave at Niah Caves. This was the setting for a 1954 expedition led by the maverick anthropologist Tom Harrison, supported by a team of guides and field researchers that included Gathorne, Earl of Cranbrook – then Lord Medway. Cranbrook’s many roles as a field zoologist included studying the bat and swiftlet populations that inhabited Niah’s Great Cave.
From this beginning, Lord Cranbrook has become one of the world’s leading experts on edible nest swiftlets and we are delighted to welcome a presentation from him as part of our online Festival programme.
In tribute to his research and lifelong support for research-led conservation we have commissioned the artist Jennifer Hall to create unique burn-out bronze casts of swiftlet nests gifted to him by the swiftlet cave owner George Nawan from Sarawak. These will form part of Jennifer’s remarkable collection of bronze nests and collagraphs in the 2020 Festival Exhibition.