There are many species of swiftlets. Traditionally, the classification of swiftlets is considered as a challenge in the taxonomy of birds and often difficult to distinguish physically. So much so to the understanding of the inherent characteristics of swiftlets.

Swiftlets are birds superficially similar to swallows, sparrows and house swifts (Apus Affinis; distinguished by their prominent white rumps) but are actually not closely related to these species at all. Swiftlets are actually from the Apodidae family and they have very short legs and do not settle voluntarily on the ground, perching vertically on surfaces like cave walls or nesting planks where they build their nests.

Among all the species, edible bird nests are built by three species of cave dwelling swiftlets, namely A. Fuciphagus, A. Maximus and C. Esculent. The nests of A. Maximus and C. Esculent, although edible, incorporate a large  amount  of  feathers and  impurities  which