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.
Coscoroba swan
The coscoroba swan ("Coscoroba coscoroba") is a species of waterfowl endemic to southern South America. It is the smallest of the birds called “swans”, but still a large species of waterfowl. It belongs to the subfamily Anserinae in the family of ducks, swans, and geese, Anatidae. It is placed in the monotypic genus "Coscoroba". The coscoroba swan is traditionally considered as an early branch from the common ancestor leading to true geese and swans, and recent genetic studies have associated a phylogenetic relationship between this species and the Cape Barren goose ("Cereopsis novaehollandiae") as sister groups.