Big, bigger, biggest

After having read this: scienceblogs.com/tetrapodzoolo…

Some giant prehistoric birds of prey, from left to right:

  Buteogallus borrasi
A bird of prey from the Pleistocene of Cuba. There's not much known about it, but we know it belongs to the genus Buteogallus, a group of buteonine hawks of which the modern day birds live in Central and South America. They're also known as crab-eaters, mangrove hawks or black hawks. The largest living specie of this genus of today is the Great black hawk, the prehistoric Buteogallus borrasi was one third bigger.

  Garganoaetus freudenthali
During the late Miocene/early Pliocene in Southern Italy this giant buteonine lived. Buteonines include true buzzards and their close relatives. G. freudenthali was the size of a golden eagle, a large bird indeed.

  Titanohierax gloveralleni (Bahaman titan-hawk)
This giant bird of prey lived during the Pleistocene and its remains (that were fragmentary) were found on Great and Little Exuma in the Bahamas. It is though to be closely related to the Black-chested buzzard eagle making it another Buteonine.
With an estimated mass of 7.3 kg this bird would be the size of a Harpy eagle, the largest living eagle of today. (female Harpy eagles can weigh up to 9 kg with a total length of 107 cm and a wingspan of 2.24 m)

  Amplibuteo woodwardi (Woodward's eagle)
This kind of eagle lived all across North America during the Pliocene and Pleistocene, also remains have been found on Cuba making it possible that this large bird's range expanded more south than first was previously thought. It's closest relatives are believed to be the solitary eagles from the genus Harpyhaliaetus, birds recognizable by their broad wings, very short tails and crested heads.
The Woodward's eagle lived on semi-arid grassland where it hunted for reptiles and smaller mammals. In size it's about the same as the Bahaman titan-hawk, making it as large as a Harpy eagle too.

  Harpagornis moorei (Haast's eagle)
With an estimated weight of 10 - 13 kg, a wingspan of 2.6 meter and a standing height of 1.1 meter this was the largest eagle ever. Haast's eagle lived on New Zeeland and was a forest living animal with short, broad wings (hence the "small" wingspan for its size) and was the top predator of its environment. It hunted all the species of moa including the giant 3 meter tall one and is even thought to maybe have preyed on the first humans that set foot on New Zeeland. 
Special about the largest eagle ever is that it's discovered to be a member of Hieraaetus, the group of smallest eagles that we know of and not related to the large Aquila eagles what was first thought. Haast's eagle's name should actually be changed in Hieraaetus moorei because of this.
The Haast's eagle went extinct because of the first human settlers only 500 years ago. We're born just too late to have seen these birds in real life...


I've tried to draw them all in scale to each other, but I'm not quite sure if it's all completely accurate. Also, the feet of my Haast's eagle are too small in comparison to the body, I think. After all this was a bird that hunted enormous animals and looking at the size of the claws of a Harpy eagle: i.imgur.com/vZOVU.jpg (who's known to hunt monkeys, sloths, anteaters etc) I think it's safe to say I made some mistakes with those...
The bird's appearances are all based on the living members of their genus or close relatives.