There are many different species of Rain Swiftlets in the world but only a small portion of them build nests which are edible. There are only three types of swiftlets which build edible bird's nests:
Edible-Nest Swiftlet Collocalia ciphaga:
This type of rain swiftlet is characterized by its brownish grey feathers, dark brown eyes and black beak and feet. They measure 10-12 cm long, their wings are long and sharp, their tails are short and squarish and they are excellent flyers. They have weak feet and all four of their claws face forward, thus making it difficult for them to walk or stand. Collocalia ciphaga swiftlets use their feet to hook themselves when resting and sleeping after attaining adulthood, just like bats and they do not live in nests. They have excellent salivary glands which secrete saliva that solidify when exposed to the air.
The purpose Collocalia ciphaga swiftlets build nests is in anticipation of the arrival of their youngs. When the nesting season is near, they begin to grow in size and secretion of saliva increases to be used as raw material in building their nests. Collocalia ciphaga build their nests three times annually and lays two eggs which are oval in shape and white in colour each time. From the construction of their nests [approximately 45-50 days], egg production [approximately 7-10 days], hatching [approximately 15 days], emergence of nestlings, feeding to independent flight [45-50 days], the whole process take about 110-120 days.
Each nest is used once only, and harvesting of bird's nests is done only after the swiftlet nestlings have grown up, able to fly and left the nests. The average lifespan of Collocalia ciphaga swiftlets is approximately 15-20 years and each pair of swiftlets can produce 45-60 nests in its lifetime.
Whether they are cave swiftlets or house swiftlets, they search for food in the morning and return to their nests by night. That is why even Collocalia ciphaga swiftlets in houses are wild swiftlets. Collocalia ciphaga swiftlets are natural enemies of insects. Their ability to catch insects is very much above other birds and animals.
Black Nest Swiftlet Collacalia Maxima:
Their scientific name is Aerodomux Maxima and the nests of these swiftlets are made of their saliva together with much of their brown feathers, thus they are known as Feather Bird's Nest. Collacalia Maxima swiftlets use the feathers found on their legs to build nests. These bird's nest pieces contain some 5-15% pure edible bird's nest. They are normally used in the production of and sold as bottled bird's nests and bird's nest pieces, loose bird's nest and broken bird's nest pieces. Collocalia Maxima are larger in size compared with Collocalia Fuciphaga and they measure approximately 11-13 cm long. The difference between them is that the former has a row of fine feathers on its lower leg and these rain swiftlets may be divided into those with red legs and those with white. They lay one egg at a time.
Giant Swiftlet Hydrochous Gigas:
Hydrochous Gigas swiftlets produce lots of saliva and they combine this saliva with fine straws to make their nests, resulting in high levels of impurities. The body of Hydrochous Gigas swiftlets is dark blue to black in colour, with luster. They are larger in size compared to Collocalia Fucuphaga and Collocalia Maxima and measure approximately 16 cm and their tails are split.
Hydrochous Gigas can be divided into house Hydrochous Gigas and cave Hydrochous Gigas and they mostly live by the sea, especially in Indonesia and the Sulu Sea in the south of the Philipines.