The great bustard, Otis tarda, is a gruiform endemic to southern and central Europe, with winter populations stretching across temperate Asia. This bustard, the only member of its genus, is one of the heaviest flying birds in the world, with males reaching over 3 feet in height and up to 40 pounds (though averages seem to center around 25). They are also one of the most sexually dimorphic bird species in the world, with males being up to four times the size of the females.
As with most birds with much larger dimorphic males, these bustards are polygamous and males compete, often quite viciously, for the rights to mate with up to five females. And like a number of gruiforms, the males strut and puff in large leks in order to gain attention of the females, who watch and choose. Males have a flamboyant and highly species-specific display routine that apparently drives the ladies wild.
The great bustard is currently categorized as vulnerable, mostly as a result of habitat loss from increased agriculturalization of its native breeding habitats.