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.
Dromornithidae
There are 7 species in Dromornithidae, the smallest species was "Barawertornis tedfordi", a bird about the size of a modern cassowary, weighing . The two species of "Ilbandornis" ("Ilbandornis lawsoni" and "Ilbandornis woodburnei") were larger birds, but had more slender legs than the other dromornithids and were similar to ostriches in their build and size. "Bullockornis planei" (the "demon duck of doom") and "Genyornis newtoni" (the "mihirung") were more heavily built, stood about tall and probably reached weights of . The largest dromornithids were "Dromornis australis" and the massive "Dromornis stirtoni" ("Stirton's thunderbird"). "Genyornis" is the best known genus.