Swifts

These masters of an aerial lifestyle forage on the rich array of plankton in the sky. Some species are so well adapted to their aerial pursuits that they cannot take off from flat ground, and some return to land only to reproduce. Using mud or adhesive saliva, swifts glue their nests—or eggs—to plants, walls, or cliff faces. These fascinating nest-building methods allow a steep descent for take-off while providing protection from predators. Like a few of their caprimulgiform relatives, some have developed echolocation for life in deep caverns and others survive periods of cold with no food by becoming torpid.