Chimney swifts are gregarious birds that build their half-cup-shaped mud nests on the inside surfaces of residential chimney flues and the smoke-shelf area above fireplaces, as well as the large boiler smoke stacks of industrial and older institutional-style buildings (in which they may nest by the hundreds). In numbers, their nests may reduce the drafting efficiency of a flue while fires are burning in the fireplace. Chimney swift chicks are very vocal when adults return to the nests with food. The raspy “chitter-chitter” sounds that frequently emanate from the fireplace are often annoying and disturbing to homeowners during the 14 to 18 days that the chicks are in the nest.
Since chimney swifts feed on flying insects while in-flight high above the tree tops, little can be done to prevent a population of these birds from returning to a locality that is favored, year after year.
Chimney swifts are federally protected under the Migratory Bird Treaty Act and, while the nests contain eggs and young, cannot be removed or disturbed without a depredation permit issued by the US Fish and Wildlife Service through the state DNR.
After the young have left the nest(s) in late Summer, a Varment Guard technician can install one or more chimney caps to prevent these birds from entering and building new nests in the future.
- Adult body length: 5 1/2 inches
- Adult body weight: about 1 ounce
- Appearance: Body black and cigar-shaped; short, wide beak
- Egg incubation period: 19 days
- Broods per year: 1
- Brood size: 4 to 5 eggs per clutch
- Birthing Period: Late April through May
- Age at which young leave nest: 14 to 18 days
- Activity seasonality: April through September
- Primary diet: Small flying insects (e.g., bees, flies, flying ants, moths, beetles)