This is the front of a commercial building in downtown Kota Bharu in northeastern Malaysia, across a river from Thailand.   The building housed a few businesses including a restaurant, a school and a showroom for a government-like office.

This is at the back of the same building where you can see a bird house 燕屋 built on top.   Note the tent erected below is probably used to deflect bird drops.

The bird house has a large window facing in the direction of the river.   It also has 'landing lights' placed above and at the entrance.   At the very top of the bird house is a set of omnidirectional speakers broadcasting bird calls to attract birds.

This gentleman had no information to offer about the existence of a bird house in the building.   The design, logistic and operations of bird houses is a trade secret.   Note the gentleman was carrying a lunch box from the 1950s era which was still widely used in Malaysia.

Hundreds of swiftlets are flying in and out of the bird house.   Typically, they leave the 'cave' during the day to forage and return to their roost at night.   Swiftlets mainly feed on insects, seaweed, and whitebait fish.

The male swiftlet 金絲燕 (Aerodramus fuciphagus) builds the nest. The female swiftlet lay 1 to 2 eggs which will take 3-4 weeks to hatch.   7 weeks after the hatching, the baby swiftlets will be strong enough to leave the nest and find their way in the world, and after 7 months, these hatchlings will find their mate to breed and reproduce.   After the hatchlings have matured, their feathered parents abandon the empty nest which is then harvested without harming the swiftlets.  

The bird nest business is so lucrative that bird houses are built even in city center in industrial and residential areas.   This building is across from the bus terminal.

Bird houses can be seen in the middle of this building where the windows are blocked, leaving a number of 'pigeon holes' for the swiftlets access.   Note the clothesline below?

Bird houses can be found all over town ...

and even in the back alleys ...

Edible bird nests are sold in specialty shops.   Indonesia is the biggest producer of edible bird’s nest in the world, producing approximately 80% of the available edible bird’s nest. The rest of the 20% comes from Malaysia, Thailand and Vietnam.

This is a box of bird nest sold for about US$60/oz.   The nutritional value of 100 g of dry nest includes 49.9 g of water-soluble protein (including amido nitrogen, monoamine nitrogen, non-amino nitrogen, arginiforne, humin, histidine, lysine and cysteine), 30.6 g carbohydrate (glycoprotein and mucin), 4.9 g iron, 2.5 g inorganic salt (including potassium, sodium, calcium, magnesium, sulfur, phosphorus, silica and other trace elements), and 1.4 g fiber (Dictionary of Traditional Chinese Medicine, The History of Chinese Medicine and the Nutrition Table).

This is the next pricier grade of bird nests.

This is an even more expensive grade of bird nests, with no price tag.

This is a sample of one of the highest grade bird nests and is not for sale.

Watch this Bird Nest TV commercial broadcasted in Asia and in the U.S.