The mountain drum
A quacking climber

Transantarctic Mountains are the longest mountain range of Antarctica, stretching from the Lorentz peninsula to the edge of the Austral forest. Due to current influences, these mountains have few precipitations across the year, being one of the driest places in Antarctica, creating a mosaic of dry tundra and polar desert. Vascular plants are very scarce, scattered in small highland bogs, creating a sort of refuge for endemic animals. Dominant vegetation mostly comprise mosses and lichens, with virtually no woody plants except a small species of willow shrub.
This arid environment is home to a peculiar bird, capable of enduring the local harsh climate: the mountain drum (Robustonris cavum).
This medium-sized ducktail is a grazer with a larger and strengthened palate to better chew the few though grasses that can survive there. Water springs are scarce, so mountain drums have adapted to not drinking for even 5 days. Guano is very dense and dry, to reduce water loss.
Both sexes possess a hollow nasal crest that is useful for warming the cold air and producing very low-frequency sounds to communicate with other individuals.
Feet are very large compared to other ducktails of the same and feathered, to avoid frost damage and more stability in steep environments. This bird can easily walk on slopes of 80% pendency. It's probably the most climbing-adapted species of bird ever, surpassing the upland moa.

Mountain drums are the most social ducktail of Polarica, with herds approaching thousands of individuals. During polar nights, it's not rare to see mountain drums resting close to each other to keep warm, in a similar way to penguins. Herds are always on the move, in search of refugial bogs, where they typically forage.
They also perform altitudinal migrations: during summers they can be found as high as 2000 meters (6500 feet), while during winter they are forced to move at no more than 500 meters (1600 feet) to escape the extreme cold and icy paths.
Infant mortality is very high, due to both frost and predation. This issue is solved by having large clutches: female drums can lay more than 10 eggs every year. Chicks are precocial, but they are fed first weeks with a special secretion of their crop, which is rich in fat and protein that help them to grow faster and stronger.
Mountain drums molt twice a year: during summer, when snow is nearly absent, they possess a short brown plumage, while during winter they develop dense and white feathers to better camouflage in the snow.