The very definition of cute. Actually, the very definition of super cute. (If Sasha Obama was a bird, she might well be a chickadee.) They are quite sociable, moving in lively chattering flocks through the trees.
Not just cute, though - they are hardy little birds who can go with the flow and thrive under conditions that many "tougher" birds couldn't endure. They are bold and fearless, going so far as to hop onto the hand of a big ol' human to grab a bit of food.
There are six species of chickadees in the US - Black-capped, Carolina, Mountain, Boreal, Chestnut-backed and Mexican. Chickadees are closely related to the titmice and share many characteristics with them.
Chickadees are mostly birds of wooded areas, though you can often find them in more open areas as long as there are nearby woods. They are cavity nesters, primarily relying on old woodpecker holes but they will also use natural cavities of appropriate size - and, of course, man-made nest boxes. Most of them line their nests with bits of fur and hair that they find. I've heard of them landing on the back of mammals to grab a few hairs - don't know if those stories are apocryphal, but it wouldn't surprise me that they'd show such boldness.
Chestnut-backed Chickadee, feeding in oak tree. This area is primarily redwood forest, with a good number of oaks, madrones, bays and toyons mixed in.
They don't just rely on cavities for nesting; because they are essentially non-migratory and spend the winter on territory, they will also use cavities for night roosts to conserve energy. Sometimes a single chickadee will find a small cavity to tuck into, but more often a group of them will roost together to use their collective body heat to keep everyone warmer. They also roost in the shelter of conifers, especially when it's a milder cold night.
A chickadee tackles a sunflower seed. They don't have powerful seed-cracking bills like finches, so they have to hold the seeds in place with their feet and pound them open.
They have a remarkably varied diet and will eat just about anything they can fit in their tiny beaks. They're seed eaters, but they also eat insects (especially when they're raising young) and come readily to suet feeders as well. In the wild, they get suet (an important winter energy source) by showing up at carcasses and taking a place at the table (so to speak) with the coyotes, ravens and other scavengers. Again, fearless. They also cache food for use in the winter months, and show remarkable abilities to relocate it months later.
Chickadees' calls may sound fairly simple to us - a few whistled notes, or the familiar "chick-a-dee-dee-dee", but they actually communicate with each other using some fairly specific language. Slight variations in vocalizations are used to warn the flock about danger, indicating the nature of the threat (hawk, snake, cat) and general direction it's coming from. Chickadees often engage in mob defense, swarming around the threat to attempt to drive it away, and this specific language lets them respond more quickly.
Another interesting thing about their song capability - the size of the "song center" in their brains changes with the seasons - growing measurably larger as breeding season approaches and shrinking when the season ends. During the breeding season, they apparently use a wider range of calls to do things like define territory and communicate with their mates. When they don't need the capability anymore, they let it lapse (one less system to support through the lean winter months?)
Bonus chickadee fun: A few years back, I discovered "Ask the Bird Folks", a weekly online (and print) column from the Birdwatchers General Store on Cape Cod. I found out about them from a column in which they answered the essential question "who's your favorite bird?" They make a great case for chickadees, but I thought you'd enjoy their list of other contenders - here are a few:
Hummingbird: Way, way,way too hyper. They need to chill.
Titmouse: A totally embarrassing name.
Catbird: It would be a good choice if it didn't have the "C" word in its name.
Great Blue Heron: Reminds me too much of Florida.
Parrots: Forget it. If you want something that talks back, get a teenager.
Falcon: No way, they eat chickadees.
Sandpiper: Too confusing.
Bluebird: State bird of New York. The Yankees live in New York.
Piping Plover: Hogs the headlines.
Goldfinch: Way too much molting. [no such thing as too much molting - lineatus]
Blue Jay: On the edge. They could snap any minute.
Baltimore Oriole: Hello. It's from Baltimore.