The Key to the Bird Nest Business Lies in Bird House [Haruka Suzuki]

The Key to the Bird Nest Business Lies in Bird House
Haruka Suzuki(Center for On-site Education and Research, Integrated Area Studies Unit, Center for the Promotion of Interdisciplinary Education and Research, Kyoto University)

The key to the bird nest business lies in houses
 The bird nest business is flourishing in urban areas along the Sarawak coast. Success in this business, which involves gathering the nests of cave swiftlets, a type of swiftlet, for sale (see Photograph 1), depends on being able to gather as many large nests as possible. To that end, people build structures that provide an environment that facilitates nest-building by the birds. Throughout this paper, I will refer to these structures as “bird house.” Unlike long-established methods for gathering bird nests built in caves, use of bird house depends on having the birds use the houses to build their nests. People employ a variety of creative measures to entice them to do so. It is no exaggeration to say that whether the bird nest business is successful—whether numerous swiftlet can be attracted to the bird house and enticed to make large numbers of high-quality nests—depends on these measures.

 In this paper, I will report on bird house (see Photograph 2) being used to conduct research in this project into the ecology of cave swiftlet. My objective is to decipher the creative measures adopted to attract swiftlet based on the placement, building methods, interior space, and interior environment of these bird houses. I conducted a site survey from February 14 to 20, 2013. The bird houses in question have been built along the road from Bintulu to Sebauh, about half an hour by car. All were recently built structures that had been completed in 2012. According to Mr. T, who manages bird house in the area, the swiftlet will come to the houses gradually in the evening. The effort is off to a good start.

 It is primarily Mr. T, his wife Mrs. D, his son B, and his daughter L who are responsible for building and managing the bird house. The actual construction of the house is carried out by several residents of Asap, where Mr. T and Mrs. D live. Asap is a region that lies about half a day inland by car from Bintulu. For his part, Mr. T’s son B lives in Kuching and operates a number of bird houses in Kuching and Bintulu. Mr. T’s daughter L lives in Bintulu, where

ツバメの巣(2013年2月15日にサラワク博物館にて筆者撮影) / An edible bird nest (Photographed by the author at the Sarawak Museum on 15, 2013)
Creative measures to entice swiftlet to visit bird house
  When people rent a condominium or apartment, they make an overall decision after comparing such factors as exposure to sunlight, floor plan, building age, rent, and proximity to the nearest train station with their own lifestyle. In the same way, is it not likely that swiftlet decide whether to take up residence in a house based on how well it matches their own “lifestyle” (ecology). In this section, I will examine the creative measures that people have implemented in order to entice swiftlet to use the houses along the lines of the characteristics of those houses.

①Location: Peatland on the outskirts of Bintulu. Good ventilation, good view. Good access to oil palm plantations.
 Mr. B, who was overseeing the construction of the bird house, chose this location because he owns land here. The land was originally owned by a nearby Iban people, but Mr. B purchased 10 to 15 acres1 of it. In Mr. B’s view, the large number of insects, on which swiftlet feed, in the peatland and nearby palm oil plantations made this site well suited for a bird house. The bird house is surrounded by untouched peatland owned by Mr. B. Palm oil plantations can be seen nearby along the road leading to Sebauh, along with scattered bird houses. There are no buildings near this bird house, which is exposed to the wind and enjoys broad views of the surrounding area.
本科研で使用しているツバメハウス(2013年2月14日にハウス南西側より筆者撮影)/ The bird house used in this project (Photographed by the author at the peat-land areas around Bintulu on 14, 2013)
②Construction method and layout: Wooden frame, threestory structure. Vaulted, open area at the entrance. Air holes ensure good airflow.
 The most noteworthy characteristic of this bird house is its wooden construction. Most bird houses are built from concrete. It is likely that this preference reflects a belief that concrete provides an environment that closely resembles the caves in which swiftlet build their nests in the first place. However, this bird house was built using wood in an effort to keep down the cost of construction. According to a site survey conducted by the author, the cost of constructing this bird house was in fact less than the cost of constructing a concrete house2.
 The exterior dimensions of this bird house (see Figure 1) are 720 (W)×1,800 (D) × 705 (H) centimeters. There are 24 air holes each on the eastern and western sides of the structure, to which PVC tubes are attached. There is an entrance for the swiftlet on the top of the northern side of the house. This entrance measures 60 (H) × 90 (W) centimeters. After comparing the size of this house’s entrance with other bird house, I found that this house has a somewhat large entrance. There are entrances to provide access for human workers to the small rooms on the south and east sides of the house. There is a control room containing audio equipment on the southern side of the house.

Figure 1: Illustration of the interior of a bird house (drawn by the author based on measurements taken at the site)

Figure 1: Illustration of the interior of a bird house (drawn by the author based on measurements taken at the site)

 This bird house was built using a simple framing method. A foundation was laid, and a subfloor was built on top of the foundation. A floor and walls of plywood were then nailed in place. The foundation is designed so as not to sink into the peatland. Normal concrete bird house require an involved process to construct their foundations, including the boring of deep holes that are then filled with stone and gravel. By contrast, this bird house uses a simple foundation construction process in which a number of wooden stakes were driven vertically into the ground. Wooden horizontal crosspieces were then secured to the stakes in the shape of a cross. While it is unclear whether this foundation construction method is sufficient absent a careful evaluation of its strength, it can at a minimum be concluded that, since the weight of the wooden house is far less than that of the concrete house, the wooden house does not require the same involved foundation construction.
 Principal building materials included Belian (Eusideroxylon zwageri Teijsm. & Binn.) and Meranti (Shorea spp., Parashorea spp.) square lumber and boards as well as plywood. Belian has been used for the foundation and the columns between the foundation and the upper portion of the house, both areas that require an especially high level of strength and durability. Meranti has been used for other structural members, and plywood has been used for the floors, ceilings, and walls. Members have been joined using screws and wedges (for columns and boards) and nails (for plywood).
 The construction methods and design of the bird house were chosen together by carpenters involved in its construction and B’s parents D and T. A particular area of discussion focused on the question of what kind of foundation to build on the loose base provided by the peatland. According to B, builders in Asap dig holes in the ground when building a foundation, insert stakes of about 2 meters in length, and secure them in place by backfilling the holes with dirt. Then horizontal members are attached to the stakes with screws to complete the foundation. Since the soil in Asap is dry, this approach provides adequate support for structures. This account suggests that they chose the construction method for this bird house’s foundation based on their experience to date with similar construction. The same observation can be made concerning not only the foundation, but also the entire house.
 The house is a three-story structure. There is a vaulted opening on the northern side, and after coming in through the entrance, swiftlet proceed into this open space, from which they move to the house’s individual floors. Each floor has an entrance/exit that opens on the western side of the house.
③Interior environment: An adequate level of attention has been paid to audible swiftlet calls and odor.
 There are about 20 speakers inside the bird house, including large speakers on both sides of the swiftlet entrance and small speakers on the tops of the columns. These speakers are connected to an MP3 player in the control room that plays a recording of swiftlet calls. The swiftlet calls played back on these speakers play an important role in attracting swiftlet to the house. The owner of the bird house has tried various speaker types and locations through a process of trial and error and creative modification in order to attract as many swiftlet as possible to the house. D described the audio equipment at a level of detail that suggested the enormous amount of attention he has paid to this aspect of the house’s design. B explained that he had obtained a good recording of swiftlet calls and that the birds would come to the house immediately if this recording were played. In this way, it seems likely that the house owners find the process of developing ideas and creatively figuring out how to attract swiftlet appealing.
 Inside the bird house, an odor that the swiftlet find attractive hangs in the air. The floors of each story are covered with the birds’ droppings, spreading an ammonia odor throughout the structure. The owners say that this odor is identical to the one that can be found inside the caves. Furthermore, the walls and floors of the house 9 Planted Forests in Equatorial Southeast Asia: have been coated with an ammonia and water solution. They explained that swiftlet would not come to newly constructed houses due to the smell of the lumber and paint used in their construction.

Family networks that span villages and cities to build bird houses
 The procurement of materials for, and the construction of, this house drew on the skills of the family network. These tasks were overseen by the families of D and T, who are the parents of B. D and T live in Asap, and they use Asap residents as labor to carry materials and perform carpentry work. Among the couple’s children, including B, are residents of Bintulu and Kuching. They take responsibility for procuring building supplies such as screws, nails, and plywood as well as the speakers and other audio equipment. Let’s briefly examine how responsibility for tasks such as procurement of materials and building work is divided among family members.

 Lumber, which is the principal building material, is harvested from a timber concession near Bakun that is owned by the lumber company run by L, the daughter. Punan people living in Bakun harvested and processed the lumber. L transported the lumber from the concession by boat down the river to Bakun and then over logging roads to Asap. Then the lumber was transported from Asap to the bird house construction site. The owners said that loading and unloading of the lumber as well as its transport at the site was handled primarily by two or three Indonesians living in Asap. On the other hand, B purchased the speakers, amplifier, and other audio equipment in Kuching and transported it to the site.

 All bird house construction work is performed by men from Asap. Farming is their primary job, but they also do carpentry work as needed. They spend about one week to build each house, sleeping at the site as they do so or traveling back and forth between the site and Asap. Five or six carpenters work at once in a team whose composition sometimes changes. Indonesians living in Asap transport lumber at the construction site. There are always two or three Indonesians at the site, and they are responsible for that work. The composition of that team is also subject to change as circumstances dictate.

Striving to create a successful example of a wooden bird house
 The above provides a brief report of what my site survey of the construction of this bird house found. It differs from other bird house in its wooden construction, but in its other characteristics it may generally be considered to compare favorably with other such structures. I learned that D and T as well as their child B played the lead role in the construction of the house, bringing together and mobilizing materials and labor from Bakun, Asap, Bintulu, Kuching, and other locations. Portions of a family network that span villages and cities are also apparent in that aspect of the construction.

 Incidentally, there are arguments both for and against wooden bird house. One group, exemplified by B, who was involved in this construction project, claims that swiftlet will occupy good houses, regardless of whether they are constructed from wood or concrete, and that wooden construction is not problematic. By contrast, Dr. L of the Sarawak Museum, who has detailed knowledge of swiftlet ecology and bird house, casts doubt on this approach, suggesting that the temperature inside a wooden house would rise and prevent swiftlet from occupying the structure. It appears that additional study will be necessary in the future in order to determine whether the house in question in fact functions as a bird house.

 Additionally, if research into swiftlet ecology continues, new methods for improving bird house based on the birds’ ecological characteristics may be discovered. I am hopeful in this respect.

1: One acre is equal to about 0.4 hectare.
2: Construction costs were calculated based on interviews of E, who owns a concrete bird house in Sadongjaya, which is about one hour by car from Kuching, and B, who was involved in the construction of this bird house.

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