Scientific name: Poecile atricapillus
Common name: Black Capped Chickadee
(Information for this species page was collected in part by Timothy Burg
(Spring 2002) and Dean Ladifian (Spring 2004) for Biology 220W at Penn State New
Black capped chickadees (Poecile atricapillus) are small birds (4.75
to 5.75 inches long with a wing span of 8.5 inches) with short, rather rounded
bodies. Individual birds only weigh between 11 and 12 grams and are marked with
a solid black forehead, crown, neck ("bib") and white cheeks. The rest of
the body is whitish to olive gray with darker grays on the wings and tail. The
black bibs of the males are larger than those of the females and can be used by
those with good vision to distinguish gender during field observations. The
bills, legs, and feet of both sexes are dark (usually black).
Chickadees are most typically found in mature forests of the northeastern and
north-central United States up through southern Canada. They migrate seasonally
within this broad, northern range spending most of the winter in the more
southern regions and most of the summer in the northern. Specific habitat
selection by P. atricapillus is governed by food supply, the presence of
suitable nesting sites, and by the need of this very small bird to avoid the
wind. Deep, dense woods, well sheltered from wind, is an ideal habitat for these
remarkably fragile birds.
On our Nature Trail, chickadees are most commonly
observed in their winter flocks (see "Winter
Birds"). These mixed species flocks (which include titmice, downy and hairy
woodpeckers, and other species) represent a significant behavioral adaptation
which increases the winter survival rates of these small, foraging bird species.
In the spring and summer, especially during the breeding season, these flocks
disperse and individual chickadees establish territories. Observations around
local bird feeding sites have confirmed the year-round presence of chickadees in
our area. They are much less obvious during the spring and summer, however,
because of their disperse distributions. Territories for chickadees range from
six to over thirteen acres. It would be easy to miss this
tiny bird in such a large habitat volume.
Chickadees eat insect eggs and larvae and are especially fond of ants. They
also consume mites, many species of small arthropods (especially spiders),
seeds, and even, in the winter, fat from animal carcasses. At bird feeders,
chickadees readily eat sunflower seeds (especially the black, oil varieties) and
suet. These tiny birds are under a considerable metabolic demand to maintain
their 107 degree F body temperatures even on the coldest days and nights of
winter. Individuals must consume their body weights in high caloric food stuffs
each day in order to satisfy their considerable energy needs. Much of their
daylight hours, then, are spent in the search for food. In good weather
conditions, chickadees cache food typically away from the edges of their forest
habitats. That way they can with relative ease recover their caches within the
shelter of deeper forest during periods of stressful weather.
Nesting and Reproduction
Chickadees nest in cavities found or excavated in both living and downed wood.
Favored tree species include birches and alders but willows, aspens,
cottonwoods, apple, and cherry are also commonly used. The chickadees may
excavate their hole themselves (usually in soft, already rotting tissue) or
quite frequently will simply move into an abandoned woodpecker cavity.
Chickadees also readily utilize nest boxes. Nests are typically found four to
eight feet above the ground but may be located as high as forty feet above the
forest floor. Complexity and age of the forest habitat is essential to generate
a sufficient quantity and quality of nesting sites. Nests are cup shaped and are
constructed from gathered mosses, grasses, bark, feathers, animal hair, and a
variety of human-made materials. Clutches of 4 to 12 eggs are laid throughout
the months of early spring to mid-summer. Eggs are incubated by the females for
eleven to thirteen days. During this time period, the male feeds the female.
After hatching, first the male and then both the male and the female feed the
rapidly growing nestlings. The young fledge in fourteen to eighteen days and
will remain with the parental pair for another three to four weeks. Flocks of
juvenile birds form through the breeding season and may become incorporated into
the multi-aged mixed flocks with the onset of winter.
Life Expectancy and Effect of Memory on Survival
The average life expectancy for a black capped chickadee is 1.5 years for a
female and 1.8 years for a male. Mortality from predation is especially high
for very young individuals but weather and accidents seem to be the primary
causes of death of all age groups. Aldo Leopold in his book "Sand County
Almanac" described one banded, black capped chickadee (# 65290) returning to his
winter feeders for five consecutive winters. He commented, though, upon the
uniqueness of this bird's long life span relative to his birth cohort and
speculated on the luck and accumulated wisdom from experience that could have
allowed this bird to live so long.
An interesting set of studies by V. Pravosudov (published in Behavioral
Neurosciences in 2002) examined the importance of memory in chickadees.
Caching, as mentioned above, is a very important behavior especially in
chickadees living in more northern (and, therefore, more weather stressed)
environments. Its is obviously important for an individual chickadee to be able
to remember where its caches are. Memory, then, would be expected to play a
greater role in the survival of chickadees in more stressful habitats than for
chickadees in less stressful habitats. Pravosudov compared the size of the
hippocampus of the brain (a part of the brain involved in memory) in chickadees
collected in Alaska (where caching and efficiency of cache recovery is expected
to be a critical factor in a bird's survival) with those of chickadees collected
in Colorado (where caching and cache recovery is expected to be of less
importance in survival). Pravosudov found that the hippocampi in Alaskan
chickadees were significantly larger than those of Colorado birds in spite of
the fact that the overall sizes of the birds were larger in the Colorado
Chickadees are preyed upon by small hawks (especially sharp shinned hawks),
owls (especially eastern screech owls), and shrikes. They also have a high
human-induced mortality due to automobiles, window strikes, chemical poisoning
(especially pesticides and herbicides), and domesticated cats.