Usually, the harvesting period of bird´s nest is separated into several months between the harvesting periods. The nests built during the first period, which is from November to March every year, are called the first-tier nests. The second period and third period follow.
First Tier (November – March)
With surplus rainfall, reproduction is promoted in small animals. Aerodramus therefore gets sufficient food supply and this strengthens their bodies, thus lead to increase saliva secretion. Impurities are extremely little. The nests are big and thick and volume is the largest when soaked. The 1st tier nests are the most precious.
Second Tier (April – Juny)
The second period for building nests. The production sites start entering dry season and the source of food for Aerodramus is reduced. Nests built are looser and the threads are less closely grouped and less dense. The shape and volume after soaking is not as good as the 1st tier.
Third Tier (July – October)
During the season of extreme dryness, Aerodramus are in their worst body condition. Saliva secretion is slow and feathers fall off quickly, thus impurities (such as feathers) increase. Smaller volume when soaked.