page_title: Chimney swift
section_title: Breeding
hierarchical_section_title: Chimney swift / Behavior / Breeding
context_page_description: The chimney swift is a bird belonging to the swift family Apodidae. A member of the genus Chaetura, it is closely related to both the Vaux's swift and the Chapman's swift; in the past, the three were sometimes considered to be conspecific. It has no subspecies. The chimney swift is a medium-sized, sooty gray bird with very long, slender wings and very short legs. Like all swifts, it is incapable of perching, and can only cling vertically to surfaces.
  The chimney swift feeds primarily on flying insects, but also on airborne spiders. It generally mates for life. It builds a bracket nest of twigs and saliva stuck to a vertical surface, which is almost always a human-built structure, typically a chimney. The female lays 4–5 white eggs. The altricial young hatch after 19 days and fledge a month later. The average chimney swift lives 4.6 years.
context_section_description: The chimney swift is a monogamous breeder which normally mates for life, though a small percentage of birds change partners. Pairs perform display flights together, gliding with their wings upraised in a steep "V", and sometimes rocking from side to side. Breeding birds arrive as early as mid March in the southern U.S., and as late as mid-May in the Canadian provinces.
  Before the arrival of European colonists into North America, the chimney swift nested in hollow trees; now, it uses human-built structures almost exclusively. While the occasional nest is still built in a hollow tree (or, exceptionally, in an abandoned woodpecker nest), most are now found in chimneys, with smaller numbers in airshafts, the dark corners of lightly used buildings, cisterns, or wells. The nest is a shallow bracket made of sticks, which the birds gather in flight, breaking them off trees. The sticks are glued together (and the nest to a vertical surface) with copious amounts of the bird's saliva. During the breeding season, each adult's salivary glands more than double in size, from 7 mm × 2 mm (0.276 in × 0.079 in) in the non-breeding season to 14 mm × 5 mm (0.55 in × 0.20 in) during the breeding season.
  Unlike some swift species, which mate in flight, chimney swifts mate while clinging to a vertical surface near their nest. They copulate daily, until the clutch is complete. The female typically lays 4–5 eggs, though clutch sizes range from 2 to 7. The eggs, which are long and elliptical in shape, are moderately glossy, smooth and white, and measure 20 mm × 13 mm (0.79 in × 0.51 in). Each weighs nearly 10 percent of the female's body weight. Incubated by both parents, the eggs hatch after 19 days. Baby chimney swifts are altricial—naked, blind and helpless when they hatch. Fledglings leave the nest after a month.
  The average chimney swift's life span is 4.6 years, but one is known to have lived more than 14 years. It was originally banded as an adult, and was recaptured in another banding operation some 12.5 years later.
caption: The nest is made of small, short twigs glued together with saliva.
exif: {}