The Black-capped Chickadee... a year-round Chicago resident who is inquisitive, friendly, chatty in a nasal sort of way, busy-bodied, hungry, seemingly happy and energetic even through harsh winter weather, and apparently in possession of some brain super-powers. When you put up a feeder they're usually the first to find it. They have many variations of their "chick-a-dee-dee-dee" call to communicate about the severity of a threat from a predator. One of few bird species that can hang upside down on foliage or tree branches, they're very busy finding food but end up stashing quite a bit of it for the winter. They'll remember thousands of hiding places and then eat up to 20 times in the winter what they eat in the summer. I guess it takes quite a bit to keep that body warm and that brain juiced to remember so much! Oh, and scientists have found that in the fall as they're feverishly stashing their seeds, their hippocampus grows 30% by adding new neurons. Then in the spring it shrinks back.
Other interesting adaptations to survive the harsh cold? They'll drop their normal body temperature of 108 degrees F to 85 in order to conserve energy. They have especially dense feathers to fluff up and trap body heat when it's cold out. They replace their feathers at the end of the summer with heavier plumage in preparation for winter. And as it gets worn out over the next year it's shed yet again.
Now I know why it's so easy to approach these birds for a close-up shot with my sub-par equipment. They're too busy gathering food and prepping for the winter to worry about me. Much to do about a lot!