> Which bird can run the fastest, up to 70 kph (43 mph)?And the answer: the ostrich. Photo credit: Diego Delso[https://commons.wikimedia.org/wiki/File:Avestruz_de_cuello_azul_(Struthio_camelus_australis),_cabo_de_Buena_Esparanza,_Sud%C3%A1frica,_2018-07-23,_DD_87.jpg], CC BY-SA 4.0 [https://creativecommons.org/licenses/by-sa/4.0], via WikimediaCommons.As the world's largest and heaviest bird, the ostrich cannot fly, andinstead is built for running. Using its powerful legs, the ostrich can sprint inshort bursts up to 43 mph (70 kph), and can maintain a steady trot at 31 mph (50kph).Ostriches are some of the oddest, yet most well-adapted large birds on theplanet. They belong in the Ratite family, which includes birds like emus, rheas,and cassowaries – all believed to have evolved from a common ancestor. Whileit's likely that their common ancestor could fly, these large birds evolved tolife on the ground as it advantaged saving energy, and more evolutionaryadaptations followed. This is likely the reason that ostriches are the fastestthings that can run on two legs. Ostriches have the largest eyeballs of any land vertebrate (yes, even biggerthan elephants!). As such, they are acutely aware of predators from greatdistances. If that wasn't enough, their powerful toe-talon can take out orthreaten any predator that strays too close. Who thought a bird could be sothreatening?While an ostrich's "fur" can look messy (and a bit goofy), its tufty feathersare actually a structural adaptation: they help keep the ostrich cool, and canbe used aerodynamically as rudders when they run at high speeds. Learn more about these giant birds below.