The term superprecocial refers to a level of physical maturity and capability in young animals that is most extreme. Examples are the Megapode birds, which have full flight feathers and which, in some species, can fly on the same day they hatch from their eggs. Another example is the Blue Wildebeest, whose calves can stand within an average of six minutes from birth and walk within thirty minutes; they can outrun a hyena within a day. Such behavior gives them an advantage over other herbivore species. For instance, they are 100 times more abundant in the Serengeti ecosystem, than hartebeests, their closest taxonomic relative. Hartebeest calves are not as precocial as wildebeest calves and take up to thirty minutes or more before they stand, and as long as forty-five minutes before they can follow their mothers for short distances. They are unable to keep up with their mothers until they are more than a week old.