The last living relatives of the dinosaurs, more often than not, live up to the famed proportions of their almost-mythic ancestors. Who would think of a gigantic sauropod or a terrifying tyrannosaur when they see a sparrow? Who would be reminded of the triceratops by seeing a crow? There are some birds, though, that, while not quite reaching the levels of dinosaurs, are giants in their own rights. Ostriches, for example, would comprehensively dwarf most humans. Moas and elephant birds, now extinct, would have dwarfed even ostriches! Here's a list of the 10 largest birds that can fly as well as those that can not fly. This is a list of the top 10 heaviest birds alive today; weight is the criterion normally used to list the 'largest' birds. Most of these are too large to fly, and many even lack the skeletal structures (a keel on the breastbone) necessary for flight. * Individuals of large swans or bustards, particularly male kori bustards, may be heavier than dalmatian pelicans, but on average the latter is heavier. Male kori bustards can reach weights of 44 lb (20 kg), but the females are significantly less massive. As you can see, most of these birds can't fly. The dalmatian pelican, in fact, may be the heaviest flying bird when both sexes are taken into consideration. Losing the ability to fly allowed these terrestrial or aquatic (penguins) birds to gain solid, heavier bones instead of the hollow bones seen in flying birds. Here are several other 'largest' birds according to different definitions of 'largest'. ► The aforementioned dalmatian pelican is a close contender for the title of the tallest flying bird in the world. However, the Sarus crane, which can grow to a height of almost 2 meters, takes the crown in that category. ► The dalmatian pelican, in general one of the largest creatures to fly, also gets a podium place in the standings for the longest wingspan. However, the wandering albatross, a bird that spends virtually its entire life airborne, has wings that can extend up to 3.5 meters that give it the title. ► If both weight and wingspan were taken into consideration, the dalmatian pelican is arguably the largest flying creature alive today. But it would be followed closely by the Andean condor, which has a wingspan larger than the pelican, and is only a couple of kilos lighter on average. These were the largest birds alive today. However, these giants are nothing compared to their extinct nonflying ancestors, which included the elephant bird (Aepyornis maximus), weighing 880 lb and standing 3 meters tall, and the moa (Dinornis robustus), which was even taller, but weighed "only" 500 lb. Good thing, these 'bird-zillas' are gone from the face of the Earth, then!