What's Cheeping In Your Chimney

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Published on: Jun. 2, 2001

Last revision: Nov. 9, 2010

nest building. Nests are about four inches across at the wall and protrude only two or three inches. Unlike some birds, swifts do not line the nest with soft materials.

Once the nest is completed, the female lays three to six (usually four or five) white eggs. The male assists with incubation, and sometimes a third bird, called a "helper," also assists with incubation and young rearing.

Hatching occurs after about 19 days. Compared with other birds of similar size, young swifts spend a long time in the nest. Their eyes do not open until they are 14 days old. Once they are 19 days old, the young begin to leave the nest and cling to the walls of the nesting shaft.

At this time, they become very vocal in begging for food when the adults arrive. They also exercise their wings in preparation for the daunting job of flying straight up. Young swifts leave the nest after 28 to 30 days.

Adult chimney swifts do not feed individual insects to the nestlings. Considering the small size of most of their prey, the parent swifts would quickly become exhausted trying to satisfy the appetites of their young. Instead, the parents collect a large ball, or bolus, of insects in a special pouch in their throat. The bolus of one Alpine swift in Europe was found to contain 600 insects. They regurgitate this ball to feed one young bird. In this way, they gorge young swifts a few times each day rather than feed them continuously the way other birds do.

After young birds have left their nests, they can often be seen flying with their parents, exchanging a characteristic stream of chatter.

Family groups combine to form large flocks in preparation for their southern migration. Some of these flocks number in the thousands and roost in large, industrial chimneys. At dusk, the flock clusters above the roost chimney in a swirling mass before dropping into the chimney. One September flock containing 10,000 swifts was observed entering a chimney in Pennsylvania. The author has also observed a flock of more than 50 birds entering a typical residential chimney. A flock may use the roost for a few nights before continuing its migration to Peru.

By the middle of October the swifts have vacated Missouri.

Tips For Living With Swifts

If you discover yourself playing host to a family of chimney swifts, some simple tips will help make the

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