The familiar namesake call of the Black-capped Chickadee (Poecile atricapillus) a simple-sounding “chick-a-dee dee dee,” is one of the most complex avian songs, much more complicated than it sounds to the human ear.
At least 16 different chickadee calls and songs have been identified, some serving multiple purposes for communicating with flocks and young. Recently, researchers from the University of Alberta in Edmonton discovered that the simple “tseet” call is a sort of “vocal identity badge,” made up of nine different sound characteristics. The chick-a-dee dee dee portrayed in a children’s song as being “happy and gay,” may in fact be an alarm call, with variations that signal different predators; the more dees, the greater the danger.
Chickadees’ large heads, in comparison to their tiny bodies, 4-5 inches head to tail, their black cap and throat, their white cheeks and tan underparts, and their grey wings and long narrow tail easily distinguish them from all other Chicago-area birds. Male and female look alike. Just a few weeks after hatching, the young are carbon copies of their parents. Chickadees are active and curious and are often the first to investigate a new feeder. They pal around in small flocks with a well-identified pecking order: the more aggressive the bird, the greater the clout.
Black-capped chickadees are native to Alaska, southern Canada, and the upper two-thirds of the continental U.S. They are non-migratory. They like deciduous woodlands, woodland edges, thickets, groves, parks and residential areas. Coming upon them away from feeders, observers will hear them chattering to each other in their acrobatic search for insects, their favorite diet. Their short, tweezer-shaped bill helps them pick insects from leaf edges, undersides of twigs and the main bark of a tree. They can feed while upside down and have specialized leg muscles that enable them to hang onto branches while feeding. They favor insects in all stages of life, particularly caterpillars, as well as centipedes, snails, slugs and spiders. When insects are less plentiful in winter, they turn to berries and seeds and visit feeders for seeds and suet. They also eat the fat of dead animals. They do not consume usually consume food where they find it; instead, they grab it and dash off to a branch to eat.
Chickadees are monogamous, using what scientists call a “mixed reproductive strategy.” During nesting season, the female may sneak away to copulate with a male with a higher ranking than that of her mate. Between their first and second seasons, scientists have witnessed “divorce,” where a female leaves her mate for a higher-ranking male.
Territories are established in spring, as the wintering flock breaks up. In early spring, chickadees start their nesting cycle. The chickadee is a cavity nester, sometimes excavating its own hole in soft, rotten wood, but often using holes excavated by other birds. They nest from mid-level to high in the canopy but typically 4-10 feet above ground. They never re-use an old nest. If trees are unavailable, they will accept an artificial nest-box. Both species excavate the hole, which may take 7-10 days. The female builds the nest using a variety of available materials such as animal hairs, cotton fibers, moss and feathers.
The female lays an average of six white eggs with reddish-brown spots and incubates for 12 to 13 days, during which she is fed by the male except for short forays off the nest. Both parents feed the nestlings, probably primarily caterpillars. The chicks fledge in 14-18 days and will remain near the nest for about another four weeks, being fed less frequently by the parents. Chickadees are faithful to their breeding grounds and, unless food is scarce, will remain near their nesting site for their entire lives.
Bird migration has garnered much scientific and popular attention. But the mystery of how birds who do not migrate survive cold winters is equally fascinating. Birds do not have the luxury of hibernating or holing up in caves during winter. They must eat every day. Birds wintering in cold climates must reduce their needs for basic survival. They exhibit species-specific behaviors, but scientists are learning about some fundamental adaptations under the skin and in the brain.
The most obvious behavioral adaptation is food caching. Chickadees may cache thousands of food items for winter, storing them individually in bark, dead leaves, clusters of conifer needles, knotholes and even dirt or snow. Most caching occurs in late summer and early fall. Chickadees seen caching in winter may just be moving previously stored high-energy food to new locations. Chickadees are able to remember their caching locations for as long as a month. Current research suggests that during cold seasons, the brain’s hippocampus may contain elevated levels of a critical hormone, corticosterone, which, along with two particular genes, may play a role in finding the many items previously stashed away.
Chickadees also employ thermoregulation. They can lower their body temperature on a cold night from the normal 108 degrees F. to 85 degrees F., lowering their energy consumption by almost 25 percent. Even in this hypothermic state, they can fly to avoid predators. Chickadees roost individually at night in tight cavities, diminishing their exposure to inclement weather.
In late summer, 2003, chickadees were among the birds devastated by West Nile Virus in Evanston, which was a WNV hotspot. These perky birds have been returning slowly, and a breeding pair was spotted in Perkins Woods this past summer.