Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother nursing her 19 day old babies in nest in tree trunk, Rocky Mountains, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother nursing her 15 day old babies in nest, Rocky Mountains, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother nursing babies in nest, Rocky Mountains, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) standing on branch, Rocky Mountains, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother protecting territory near her nest from other squirrels, Rocky Mountains, North America

Michio Hoshino / Red Squirrel (Tamiasciurus hudsonicus) feeding atop tree stump, Alaska

George Sanker / American red squirrel (Tamiasciurus hudsonicus) feeding in meadow. Acadia National Park, Maine, USA. May.

Alan Murphy/ BIA / Boreal Chickadee (Poecile hudsonicus) pair flying, Alaska

Donald M. Jones / Red Squirrel (Tamiasciurus hudsonicus) in summer, Montana

Donald M. Jones / Red Squirrel (Tamiasciurus hudsonicus) feeding on mushroom, Montana

Donald M. Jones / Red Squirrel (Tamiasciurus hudsonicus) in summer, Montana

Donald M. Jones / Red Squirrel (Tamiasciurus hudsonicus) feeding in winter, Montana