Globe Moss and Frog Bunnies of the Sea Ice (Patreon)

Some miscellaneous worldbuilding for the avian homeplanet. The poles both have permanent sea ice fields, which are difficult to colonize for life for the same reason sand dunes are. The surface constantly shifts (although much slower than a dune) as it's shaped by wind, currents, melting, and precipitation. 

In the North pole, the dominant ecosystem on the ice is globe fields, which are full of rolling balls of moss and frost tolerant worm plants. They very slowly roll across the ice, being pushed uphill by the worms into sunlight as they slowly melt whatever ice they sit upon. 

All of the moss globes are host to suite of small cold tolerant invertebrates, but a small fraction are also nests for globe bunnies. These small endotherms hollow out the inside of mossball and pack it with insulation. They feed voraciously on invertebrates and other mossballs, though they will also trim the "lawn" surrounding their house, to keep it at a manageable size and roundness for rolling about. 

Polar avians find the bunnies tasty. The second image features one of the larger coastal cities on the North pole landmass. It is essentially one large interconnected building, in classic polar avian style.