Both parents take part in the building and, as mating time approaches, their salivary glands swell greatly. Having chosen a suitable rock face, they birds fly to it, turns to dab it with saliva, tracing the outline of the base of the nest. Their saliva is sticky and thread forming. Each layer quickly dries and, as it does so, another layer is dabbed on top, gradually building up to form a white translucent cup shaped into the curve of the rock.
Tuesday, March 27, 2007
The swiftlets of southern Asia and Indonesia are creatures of the air, awkward on the ground but total masters of aerobatics. Even their nesting places have an aerial quality, often being no more than the sheer wall of a cave without benefit of ledge or cranny. Not that they require them, for unlike other birds, they neither collect nor use building material, but produce it entirely by themselves.