I probably saw one of these around 2010 while sailing up the Saigon river towards Ho Chi Minh. They looked rather menacing and I wondered what they could be.
I managed to take a video in 2015 which you can see above (I apologise for the poor quality of the video ). The background noise makes it difficult to hear the incessant chirping of the inhabitants. These structures are “bird houses” designed for the collection of their nests for birds’ nest soup.
These birds are a special breed of martins. They secrete a sticky mucus when building their nests and this is what gives them their particular gustative appeal.. Why anyone should have thought of eating one of these in the first place, and like it, is beyond me. However, eating them has mutiple health benefits according to Chinese culture. Gathering the nests in nature is a perilous occupation as these birds live in the tops of deep caves. I have seen photos of precarious bamboo ladders used by the collectors at some incredible height. Although dangerous, the occupation is kept within the family, as a kilo of birds’ nests can sell for several thousand dollars and the caves are under surveillance against poachers.
The gathering of nests takes places in many parts of Southeast Asia, wherever the environment is suitable. The photo above shows that a certain cave” belongs” to John Wariysn (sic) in Triton bay, Western Papua, Indonesia.
In Vietnam, an easier solution has been found. These large buildings , “bird houses”, are erected to mimic the normal environment of the birds. The constant chirping is in fact relayed over a PA system to attract the birds. Nests are collected up to three times a year, which forces the birds to build new ones. This is rather stressful for them and may pose problems in the long run, but the risks inherent in the harvesting of nests have practically disappeared.
The two photos above were taken in 2022 in central Vietnam, near Quy Nonh, which shows how this type of building is getting more and more common.
Obviously, the nests need to be cleaned to be fit for human consumption: this is what you can see in the two photos above, taken in Hoi An. Once this has been done, the nests are put on sale…for those who can afford them!