The Habits and Habitat of Chickadee Birds

Your average chickadee, a fidgety puff of mostly feathers
and bone, weighs about one-half ounce. How do these tiny
birds routinely survive frigid days and freezing nights?

In autumn, chickadees, like other small birds, grow a
thicker coat more — small, downy feathers, with lots
of heat-trapping air spaces. By winter, the birds have
gained 25 percent more plumage. On a cold day, chickadees
fluff up these feathers to at least an inch. The result is
a downy ball of a bird, its spherical overcoat
astonishingly effective. At 10 degrees below zero, the
difference between a tiny chickadee’s body temperature (108
degrees) and the outside air — just an inch of
insulating feathers away — is 118 degrees.

Of course, it takes quite a furnace to generate and
maintain the bird’s high body temperature. Indeed, the
chickadee is a metabolic fireball. Its heart beats 500
times a minute — at rest. Given intense activity, the
rate doubles to 1,000 beats. Even when perched, the little
chickadee is never still, cocking its head, shifting its
feet. And beneath all those feathers, the bird continually
flexes its chest muscles, shivering to generate yet more
heat.

Chickadees at Night

Being all fired up is fine during the day when the sun is
up and there’s food to be eaten. But come sundown every
winter day, the bird faces 12 or more foodless hours of
dark and cold. How does it cope? First, by holing up in a
tree cavity. Chickadees are the only birds besides
woodpeckers who excavate their own holes. A cavity just big
enough for one bird to cram its body and its fluffed
feathers into is perfect. Watch your bird feeders in the
morning for chickadees with rumpled tail feathers —
the result of a night spent in cozy quarters.

Even with the best shelter, a chickadee also must sustain
its inner fires through the night or perish. Chickadees
don’t have a crop in their throats to store food that is
slowly digested while sleeping. Instead, they turn down
their internal thermostats, conserving energy and saving
fuel. They reduce their need for food and oxygen on cold
nights by going into a state of controlled hypothermia,
lowering their body temperature by as much as 20 degrees.

Chickadees’ Massive Memory: Scatter Boarding Food

Regardless of the birds’ nighttime energy efficiency,
during the day the tiny fliers must eat almost constantly
to feed their furnaces and put on enough surplus fat
— about 10 percent of their normal body weight
— to get them through another night.

Because they need a lot of food, especially when the days
shorten and sustenance becomes scarce, chickadees spend all
autumn gathering and storing food. Unlike many woodland
food hoarders, chickadees don’t put most of their
provisions in large caches. Instead, they hide one or two
tidbits at a time in separate locations over a wide
territory. Biologists call this behavior “scatter
hoarding,” which, they contend, ups the odds of survival.
If a competitor finds one stash, all is not lost —
there are many more scattered stockpiles.

So in fall, each chickadee works to fill its own
multi-acre, here-and-there food pantry. It readies insect
prey by plucking off the heads and wings, then stuffs the
bodies beneath bits of loose bark or inside curled leaves.
Tiny seeds are wedged beneath layers of lichen; pushed
between evergreen needle clusters; poked into the ground.
(You can witness this behavior at your own feeders during
autumn. After filling their bellies in the morning,
chickadees will spend the rest of the day shuttling
sunflower seeds to hiding places)

The sheer scale of the birds’ winter food-preparation
activities is astonishing. Carolina chickadees and others
that live where winters are relatively mild may store
several hundred separate food items. Chickadees in the
North or in mountain regions will hide several
thousand tidbits in as many locations.

Even more remarkably, chickadees remember precisely where
they’ve stored all that food. Experts once thought the
birds retrieved stashed goodies more or less by chance. But
researchers have found the chickadee that hides a given
meal in a given place is the same chickadee that returns
— sometimes months later — to gobble it up.

How can a bird with such a small brain remember the precise
locations of so many food caches? If you’ve ever played the
game of Concentration — or simply tried to keep track
of where you put your car keys — you can begin to
appreciate the feat.

Chickadees grow fresher, better brains every autumn, when
they need the extra recall power. Old brain cells die off,
essentially wiping the slate clean, while new brain cells
generate rapidly to replace them. The hippocampus, the area
of the brain responsible for memory and spatial
relationships, becomes larger, giving the bird a greater
ability to mentally map its home territory and cache
locations. Later, in spring and summer when fresh food is
available, the bird’s hippocampus shrinks to its normal
size.

So much for the notion of “bird brain.” The chickadee’s
renewable brain, with its ability to produce new neurons
each year when needed, then discard them when not, may
eventually point researchers toward better treatments of
Alzheimer’s disease and other degenerative brain maladies.

Behavior: Chickadee Flocks

Like most birds, chickadees are monogamous. They live in
pairs during spring and summer, their breeding season. Each
couple claims and defends a territory of several acres.

But in fall, chickadees form winter flocks typically
containing six to 10 birds — usually with equal
numbers of males and females, which are paired. A flock
isn’t a family, but a sort of neighborhood association of
chickadee couples. Within the flock, male chickadees rank
above female, older above younger. The top-ranked chickadee
— usually an elder male — gets to eat first at
a feeder, and can chase away any other flock member. The
second-ranked bird can lord it over all those below it, and
so on.

You can watch the chickadees’ intriguing behaviors and
social dynamics in back yards across the country. I
confess, though, that what I most admire about chickadees
has little to do with natural science and more with sheer
pluck.

See for yourself some somber winter’s day. Check out the
chickadees — ever busy, always chipper, in a colder,
harsher place than you, but making the best of it just the
same.

Amazing how such a little bird can lift our spirits.