It is red because of blood mixed into the spit of the swift. As
nests are harvested, the swift has to rebuild its nest and this
takes a physiological toll on the bird (because the eggs, which are
not yet laid great tax the bird's system).
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Some time ago people believed that a red nest was created by an
overworked Swiftlet that had built its nest partly with blood.
Nowadays, people believe that the red nest is created by a Swiftlet
that has eaten seafood or a food substance which contains a high
volume of iron. Research has proved both of these beliefs to be
untrue. The red nest (red blood) is not created by the Swiftlet,
but by the surrounding environment.
Cave nests turn red in colour due to the mineral content and the
wet surface of the cave which seeps into the nest. This polluting
of the nest by cave water significantly reduces the nutrient levels
of the nest. The red appearance of a house nest is achieved through
the unethical dying of white nests. The harvest is deliberately
delayed to let the gas from the Swiftlet's droppings react with the
nest. The gas emitted by the Swiftlet is called Ammonia. Ammonia is
a compound found in fertilizer and detergent.
Long term consumption of bird's nest which has been contaminated
in this way will have adverse effects on personal health. The
consumption of toxic chemicals has strong links to cancer and other
major illnesses. This is the reason all bird's nest experts advise
expectant mothers and the elderly to avoid the consumption of red
nests.
****
The above is based on researches and reports released by
Pureness Bird's Nest
