Gray-rumped Swift

Quick Facts

  • Scientific Name: Chaetura cinereiventris
  • Spanish Name: Vencejo de rabadilla gris
  • Family: Apodidae
  • Known Nicknames: Gray-rumped Spine-tailed Swift
  • Average Length: 11–12 cm / 4.3–4.7 in
  • Average Weight: 15–22 g / 0.53–0.78 oz
  • Wingspan: 25–30 cm / 9.8–11.8 in
  • Key Feature: Pale gray rump contrasting with dark body and wings
  • Primary Diet: Insectivore (aerial insects)
  • Range: Costa Rica to central Bolivia, Amazon basin, and Atlantic forest of Brazil
  • Habitat: Lowland and foothill tropical forests, often near water
  • Social Structure: Highly Social (forages and roosts in flocks)
  • Nesting/Breeding: Tree cavities, hollow trunks, or under eaves of buildings
  • Conservation Status: Least Concern (LC)
  • Population Trend: Stable

The Gray-rumped Swift (*Chaetura cinereiventris*) is a master of the aerial realm, a small, cigar-shaped bird built for life on the wing. Its general appearance is a study in subtle contrast: a sooty brown to blackish body is dramatically offset by a conspicuous pale gray rump patch and a lighter gray throat, giving it a distinctive "saddled" look. Unlike many birds, it possesses tiny, weak feet and a stiff tail with protruding spine tips, which it uses to cling vertically to the rough bark of trees or the walls of chimneys—its only respite from constant flight. A special feature is its incredibly fast, stiff-winged flight, often in noisy, chattering flocks, where it tirelessly hunts for flying ants, beetles, and other insects high above the forest canopy in its Central and South American range.

Fun Facts

The Gray-rumped Swift is a master of extreme aerial living: it spends virtually its entire life on the wing, even mating and gathering nesting material while flying. Unlike most birds, it has a unique adaptation of asymmetrical wingtips, with the outer primary feathers longer on one side, allowing for incredibly agile, rapid turns to snatch insects in dense canopy. Quirkily, it builds its tiny half-saucer nest entirely out of saliva and bits of lichen, gluing it to vertical tree trunks or inside hollow snags, and both parents share the duty of incubating their single egg by pressing it against their brood patch while clinging to the nest wall.

Habitats & Distribution

The Gray-rumped Swift is found from Nicaragua south through Central America, across much of northern and central South America, including Colombia, Venezuela, the Guianas, Ecuador, Peru, Brazil, and Bolivia, and also on the islands of Trinidad and Tobago. It inhabits lowland and foothill forests, particularly humid tropical rainforests, as well as forest edges, clearings, and semi-open areas near water. It is also commonly seen over rivers, lakes, and human settlements, often foraging in the airspace above towns and cities. This species generally occurs from sea level up to around 1,500 meters in elevation.

Behaviours & Reproduction

The Gray-rumped Swift is a highly social and colonial species, often nesting in small groups on vertical surfaces like cliffs, hollow trees, or even human-made structures. Mating pairs are monogamous for a breeding season, and courtship involves high-speed aerial chases and synchronized gliding displays. The nest is a shallow cup of twigs and saliva, glued to a sheltered vertical wall. Both parents share incubation of the single, elongated egg for approximately 18-20 days. A unique reproductive strategy is their reliance on a single-egg clutch per brood, which is rare among swifts; this likely reduces competition for food in their insect-rich but unpredictable aerial environment. Chicks are altricial and are fed regurgitated insect balls, fledging after about 28-30 days. After fledging, young may remain with the colony, possibly helping to defend the nest site the following season, though cooperative breeding is not formally documented.

Diet

The gray-rumped swift (Chaetura cinereiventris) is an obligate insectivore, feeding exclusively on a diet of small flying insects captured in mid-air during continuous, rapid flight. Its menu primarily consists of various flies, beetles, bees, wasps, ants, and termites, often taken in large numbers during synchronized emergence events. An interesting aspect of its diet is the swift’s ability to consume prey that are toxic to many other birds, such as certain stinging hymenopterans, without apparent ill effect. Additionally, these swifts are known to drink water on the wing by skimming the surface of lakes or rivers with their lower mandible, a behavior that complements their aerial feeding strategy.

Colors

The Gray-rumped Swift has a sooty brown to blackish body with a contrasting pale gray rump patch. Its throat and upper breast are lighter, often a pale grayish-brown, while the wings are long, narrow, and uniformly dark. There are no distinct markings or patterns, and its subdued, countershaded coloration provides camouflage against the sky and dark forest backgrounds.