To nest or not to nest
Known and named after their edible nests, certain species of Swiftlets in India and SE Asia have seen their homes being illegally harvested for centuries for commercial gain. Experts recommend that a regulated process of harvesting would serve to benefit not just the aves but deserving people from the local community as well.
With a fairly wide home range, the Edible-nest Swiftlet (Aerodramus fuciphagus) is distributed throughout the archipelago of Indonesia, from Andaman & Nicobar Islands in the west to Timor Islands in the east, along with the Malayan Peninsula, Borneo and surrounding islands, and the South-eastern coast of Asia. The A. f. inexpectatus is the subspecies of the Edible-nest Swiftlet endemic to the Andaman & Nicobar Islands.
This tiny bird has a unique adaptation—it makes nests by using its own saliva. Unfortunately, this rather singular trait is also what threatens the survival of this species. In the 16th century, the nest became a delicacy in Chinese cuisine and was also believed to have several medicinal properties, including prolonging and rejuvenating life and being a powerful aphrodisiac. Ranked among the most expensive of wildlife products (approximately $4000/kg) and hence said to be a ‘food for kings’, the nest is also nicknamed ‘white gold’ in the wildlife market because of its appearance. But it is only in the last two-three decades that production of the bird’s nest has reduced drastically because of over-exploitation and uncontrolled harvesting. The high demand on the nest has brought down the population of the Swiftlet by 80-90% and close to local extinction across some of its distribution range.
What’s in a Nest?
The nest, on an average, contains 9% moisture, 20% inorganic ash, 32.3% protein and 38.7% carbohydrate. After some early analytical studies, extracts from the nest were used as a substrate to investigate viral sialidase activity. More recently, the avian epidermal growth factor (EGF)-like activity was noticed in a partially purified swiftlet-nest extract. It has been suggested that this water-soluble glycoprotein might influence more than one physiological parameter to affect its purported medicinal properties.
These swiftlets nest in caves, attaching their sticky homes to the cave walls and ceiling. The nests are numbered to follow their condition and fate through the breeding season.
Of the 16 species of swiftlets, only three make edible nests. The Edible-nest Swiftlet exclusively uses saliva to build the nest, which gives it a white, opaque appearance and is therefore called a ‘white-nest swiftlet’. The Indian and the Black-nest (Aerodramus maximus) Swiftlets use saliva to bind their feathers and other materials, giving their nest a black or dark-coloured appearance, and are hence called ‘black-nest swiftlets’.
Swiftlets in Andaman and Nicobar
The Edible-nest Swiftlet is identified as a high-priority species for conservation action in the Andaman & Nicobar Islands. A preliminary survey (1995-97) conducted by Salim Ali Centre for Ornithology & Natural History (SACON) showed that the only realistic way to conserve this species was by organising and supervising nest collectors in the management of swiftlet colonies, with the incentive of harvesting the nests post-breeding. SACON found that the population had declined by more than 80% over the past few decades due to uncontrolled nest collection. In the Andaman Islands, over 98% of the nesting caves showed signs of intensive nest collection, while in the Nicobar Islands it was over 67%. Caves with very small populations (1-3 nests) were the only ones with no collection activity; however, nest collectors were aware of all swiftlet caves.
A programme to conserve the Edible-nest Swiftlet in the Andaman & Nicobar Islands has been underway since 1999 and is being implemented by the Department of Environment and Forests, Andaman & Nicobar Islands and SACON. Conservation strategies undertaken include organising and motivating nest-collectors to protect caves round the clock for the duration of the breeding season and developing alternate populations of the Edible-nest Swiftlet in private houses, both to increase populations as well as to augment livelihoods.
In-situ conservation
Taking into account the accessibility and availability of nest collectors and caves with a substantial population, the in-situ conservation programme was initiated with 28 caves at Chalis-ek, near Ramnagar in North Andaman, and one cave on Interview Island in Middle Andaman. At the base of the conservation effort are the nest collectors, who were organised into forming around-the-clock protection force for over six months to ensure successful breeding of swiftlets. Research and monitoring are continually undertaken and all nests are numbered, their histories maintained and regularly checked. The incentive to the erstwhile nest poachers for effectively protecting the caves and swiftlets was the grant to collect nests once the breeding was completed. The harvesting system is managed scientifically with the help of the nest protectors. The conservation strategy has resulted in positive changes on the ground. In the 29 caves where this strategy is being implemented since 2001, the population has more than doubled. Additionally, 175 caves were included in the programme, and since 2010, more than 60% population recovery has been observed. In some caves which are being monitored and where this innovative conservation programme is not being implemented, a population decline of over 50% and in some cases even extinction have been noticed.
The tiny Edible-nest Swiftlet incubating its eggs inside the nest
Ex-situ conservation
A method for the conservation of swiftlets in houses has been devised, where existing nests of Glossy Swiftlets are used, or new structures are built to attract Glossy Swiftlets. Eggs of the Edible-nest Swiftlet are then transferred from specifically protected caves to the nests of the Glossy Swiftlet, who act as foster parents, incubating the eggs and rearing the young Edible-nest Swiftlet. As swiftlets are parochial, the Edible-nest Swiftlets return to the house for nesting when mature; establishing a new population of the species. The houses practising this in Southeast Asia are privately owned, while in India, locations safe from indiscriminate nest harvesters are used. Swiftlet ranching generates significant revenue for local economies as well as considerable employment opportunities in the cleaning, processing and packaging of swiftlet nests. The initial process of establishing a population of Edible-nest Swiftlets in a house at Tugapur was a successful one. Today more than seven breeding colonies in urban areas have been established throughout the Andaman Islands.
The ex-situ conservation strategy proved to be a success when the weaned Edible-nest Swiftlets returned to their birth site and started nesting next to the Glossy Swiftlet nests
Treasure Gathering
The Edible-nest Swiftlet was listed as a Schedule-I species of the Wildlife Protection Act (1972) in 2002. This hindered the ongoing successful implementation of the in-situ conservation programme and also disallowed the nest protectors to collect nests after breeding, naturally demoralising them. Finally, after seven years of appeal, the species was conditionally delisted from the endangered list, but only for experimental purposes. Since then, the post-breeding harvesting of the nest is practised, but the nests remain with the forest department. Once the breeding season is over, the nest mostly falls off from the cave wall or ceiling as it loses its adhesiveness or sometimes gets degraded at the site.
During the next breeding season, the bird constructs a new nest at the same site. The enlargement of the salivary glands during each breeding season must be an adaptation developed to suffice the requirement of constructing a fresh nest every season. As a result, post-breeding harvesting of the nests does not disturb the species in any way, unlike with other animals. Nonetheless, the harvesting has to be managed scientifically and sustainably.
With remarkable success for almost one and half decades, it is recommended that the programme is expanded and continued with a scientific approach, in other sites in the Andaman and Nicobar Islands. However, we must also work out a way to offer incentives to the nest protectors and ex-situ house owners of the Andaman & Nicobar Islands for their aid in the conservation of this unique species. For long-term protection of the swiftlets, the expertise and knowledge of locals and their involvement can be truly invaluable.
Other swiftlets in India
Besides the Edible-nest Swiftlet, there are three other species of Swiftlets found in India. The Indian Swiftlet (A. unicolour) is endemic to the Western Ghats and Sri Lanka and builds black edible nests using saliva and its own feathers. The Himalayan Swiftlet (A. brevirorostris) lives along the lower altitude Himalayan mountains and maybe a migrant to the northern part of the Andaman Islands. This swiftlet uses very little saliva while constructing its nest, mostly composed of plant material. The Glossy Swiftlet (Collocalia esculenta), also commonly found on the Andaman & Nicobar Islands, uses moss, twigs, leaves and flowers to make a nest, and saliva to bound the nest together and to stick it to the rock surface.
Echolocation
Swiftlets, along with the South American Oilbirds, are the only aves to use echolocation. Unlike in bats, the echolocating ability of swiftlets is poor, hence used only in the dark. The sound waves used by swiftlets for echolocation are between the range of 1-16kHz, and hence they are audible to human ears. With this poorly developed sense, swiftlets can recognise anything bigger than 15cms in their way in the dark.
Late Dr Ravi Sankaran (1963-2009)
Dr. Ravi Sankaran is a renowned ornithologist who developed his own unique and effective approach to wildlife conservation issues. He was involved in the conservation of several charismatic and endangered birds like Lesser Florican, Nicobar Megapode, Narcondam Hornbill and Edible-nest Swiftlet. It was Dr Sankaran who, with his unique line of thinking, designed the in-situ and ex-situ conservation programmes for the Edible-nest Swiftlet in the Andaman & Nicobar Islands, which was put into action in 2001. The conservation efforts described in this article were largely executed by Dr Sankaran.
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