Smallest organisms
With a mass of approximately and a length of 5 centimetres (2.0 in), the bee hummingbird ("Mellisuga helenae") is the world's smallest bird species and the smallest warm-blooded vertebrate. Called the "zunzún" in its native habitat on Cuba, it is lighter than a Canadian or U.S. penny. It is said that it is "more apt to be mistaken for a bee than a bird". The bee hummingbird eats half its total body mass and drinks eight times its total body mass each day. Its nest is 3 cm across.
Least grebe
The least grebe ("Tachybaptus dominicus"), an aquatic bird, is the smallest member of the grebe family. It occurs in the New World from the southwestern United States and Mexico to Chile and Argentina, and also on Trinidad and Tobago, the Bahamas and the Greater Antilles.