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Archive for Sunday, April 25, 1999

BIRD OF THE MONTH

April 25, 1999

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Kansas chickadees are actually a variety of species.

Kansas chickadees include mountain chickadees, black-capped chickadees, Carolina chickadees, or both of the latter two. A fourth Kansas species, the tufted titmouse, is almost a chickadee, but is not as closely related to the others as they are to themselves.

Mountain chickadees are casual in western Kansas, wandering in from Colorado. Black-caps occur commonly in the northern 90 percent of the state and Carolinas in the southern fraction, which is also where they hybridize. Black-caps and Carolinas share a relatively recent ancestor, as well as many ecological and behavioral adaptations.

Comparative ecology

These three species along with the titmouse are birds of woodlands and woodland edges. The Black-capped chickadee and titmouse are regularly found together over the eastern half of Kansas. They have occasional interactions over resources, which generally are taken over by the titmice, birds larger and more physically competent than chickadees.

The black-cap has an enormous range, from Alaska to Newfoundland south to northern New Mexico and easterly to Pennsylvania, with a distributional finger extending south at high elevations in the Great Smoky Mountains.

From Kansas eastward, black-caps interbreed with Carolina chickadees, a slightly smaller bird. Hybrids have little loss in overall capabilities, and some populations seem to be composed entirely of hybrid individuals. Tufted titmice occur in the eastern half of the United States, and extend into northeastern Mexico south to Veracruz.

Comparative behavior

All three species are residents where they live, and for black-caps in the north this means overwintering under extreme conditions. Such small birds can be challenged by low temperatures -- they have a large surface area relative to body mass -- but black-caps successfully manage the problem. They sleep in old nesting cavities, tuck their heads under the scapular feathers, and can lower their body temperatures at night, saving energy. They, as well as other chickadees and titmice, also store food in nooks and crannies, stores that can be important in stormy weather.

Wintering chickadees generally move through a considerable area, so they must have good memories if they are able to relocate food caches. In fact, chickadees are known for their mental agility. Captive blue tits, close relatives living in Europe, became famous in the 18th century for learning how to feed themselves in tall, thin cages. When their food was provided in small baskets hanging on strings beneath their perches, the birds got to the baskets by pulling up the strings with their beaks, gathering the loose loops against the perch with their feet.

Our chickadees probably would show the same kind of behavior if they were put to the test (which is generally not possible these days, owing to our rational laws regulating human interference with birds). Our chickadees are not known to be mentally inferior to their European cousins, and could almost certainly show off if kept caged and forced to learn new tricks.

Nests and eggs

Chickadees and the titmouse are hole-nesters. They excavate cavities in rotting deadwood such as in broken tree limbs. They may also appropriate abandoned woodpecker cavities. Hole-nesting is a relatively safe way to care for one's eggs and nestlings, as compared to using exposed nests.

Chickadees and the titmouse lay around five eggs in a clutch. The earliest nesters are already incubating their eggs by late March. The peak in nesting activity occurs in April, but a few nests, perhaps replacing earlier ones lost to predation, may be found as late as June.

Young chickadees leave the nest, never to return, about two weeks after hatching, and stay in a group with parents for up to another month. Young attain feeding skills in that period, although initially all their food is brought to them by the adults.

Young birds disperse as individuals, usually moving less than a quarter-mile from the nest. Young soon form into flocks, occasionally as large as a dozen birds that will persist through the fall and winter. These flocks also will include older birds, so that juveniles have continual exposure to adult role models throughout their first year of life.

Social contacts are complex, and the young birds usually find their future mates in the winter flocks. Flocks break up in late winter-early spring, and pairs tend to find nesting cavities within the range of the wintertime flock. A pair of chickadees almost always stay within the territorial range of the first nest for as long as they live.

Chickadees and the titmouse are similar in other ways, but have some important differences.

Young titmice may stay with their parents in fall and winter, and do not make large winter flocks with other titmice. Young from other territories may also join a family group, but such flocks are mostly of five or fewer birds.

Young birds about a year old may also assist parents in raising another family. Such young are not sexually active, so far as is known, but they help feed the nestlings and they participate in alarm behavior when predators are sighted. This is called cooperative breeding, and is uncommon among species of chickadees and other tits.

Because of the way humans live -- fracturing forests, creating agricultural fields and pastures, building cities and suburbs, a great amount of habitat for chickadees and titmice has been created in Kansas and the United States in the past 300 years. These birds probably are more abundant now than when the continent was colonized by European humans.

Aside from predators, chickadees have few problem species to contend with -- one of which, not surprisingly, is the tufted titmouse. Because titmice are fairly close relatives of chickadees, they tend to use a similar set of resources, and when competition occurs, the titmice win. Chickadees may have their populations limited under these conditions, largely because good nesting cavities are not easy to find.

Both species have another problem, which is the house wren. Wrens also like to nest in cavities, and aggressively take over good sites from both chickadees and titmice. If the latter already have eggs in the nest, wrens destroy them by puncturing the shells. Chickadees and titmice are intelligent and capable birds, but they have not solved the problem of house wrens.

People and chickadees

People interested in chickadees and titmice can erect nestboxes, so that either species might be able to nest near them. Nestboxes may be the only sites available for nesting in urban neighborhoods, in which dead trees and branches usually are removed, leaving the birds with few options for nest sites.

Nestboxes with holes no larger than 1 1/4 inches in diameter will exclude house sparrows but allow chickadees to enter. If the inside is half-filled with sawdust and wood chips, the birds are further attracted to it.

If nestboxes are put in place in winter, chickadees would be able to use them in late March, before wrens arrive from the south, and chickadees could have a successful nesting before the wrens become a problem. With well-maintained nestboxes and a bird-feeding station, even city people could readily have chickadees year-round.

-- Richard F. Johnston, is professor emeritus at the Kansas University Natural History Museum and Biodiversity Research Center and a member of the Kansas Ornithological Society.

Bob Gress/Great Plains Nature Center Photo

1. -- Black-capped chickadee

2. -- Tufted titmouse

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