Brontosparrows
Kings of the north

Ground tyrants are cosmopolitan in Antarctica, being found from the hotter rainforest to the coldest dry tundra. However, in warm northern latitudes, some species have reached gigantic sizes, forming a paraphyletic group called Brontosparrows.
The group comprises herbivorous, omnivorous and carnivorous species, with the largest being the mediterranean brontosparrow (Giganotopasser struthiomimus).
It's a bird about as high as an ostrich, but more robust and heavier; it dominates Ronne Bay's scrub landscape, where they feed mostly on grasses and foliage. They are highly cursorial, capable of outrunning most of the terrestrial geotters, but they can also fight back with strong kicks. Few cambiocenic predators have the gut to attack a healthy adult, but juveniles can be easily preyed on by temperate tyrannus (Carnipasser gracilis), one of the few carnivorous species of brontosparrows.
While resembling in size herdstalkers and wardrums, temperate tyrannus' ecology is more similar to a giant stiltpecker: they are too gracile to bring down large prey, but they are perfect to chase at high-speed small-medium sized vertebrates. They have a wide distribution that covers the entire sub-tropical environments of Neopolarica, including northern mossyforests, where they feed also on the chicks of another giant bird: the forest brontosparrow (Brontopasser forestalis). It's a browsing tyrant that feeds on leaves, buds, fruits and seeds and it's strictly related to the mediterranean brontosparrow, but it hardly reaches half its size.
Like their ancestors, forest brontosparrows are highly communicative and live in small dynamic groups, which are not led by any individual. These herds can break up and reform after a predator attack: this bizarre strategy probably developed to prevent stampedes, which can become dangerous for the entire herd in the closed and tangled undergrowths of the antarctic rainforests.
The typical call of forest brontosparrows is a short and repeated peep that can be heard at miles of distance, even under the heavy rain that frequently affects their ecoregion.