Chimney swifts and bats are both small, fast-flying creatures that inhabit the skies at dusk. They have similar silhouettes and flight patterns, which can make differentiating between the two difficult for casual observers. However, there are several key differences in appearance and behavior that can help identify whether a mysterious flying creature is a chimney swift or a bat.
Size and Shape
The most noticeable difference between chimney swifts and bats is their size and proportions. Chimney swifts have very short legs, with tiny feet that are mostly useless for perching. They have long, slender, curved wings and a short, rounded tail. Their bodies are cigar-shaped and very streamlined. Chimney swifts measure 5 to 7 inches (12 to 17 cm) from bill to tail tip.
In contrast, bats have longer legs with clawed feet that allow them to hang upside down when at rest. They also have short, broad wings and a longer tail. Bat bodies are more flattened and oblong compared to the tubular shape of the swift. Wingspans range from 8 to 16 inches (20 to 40 cm) depending on the bat species.
In Flight
When in flight, chimney swifts have a very stiff, shallow and rapid wingbeat. Their wings maintain a gently curved shape as they flutter quickly. They appear hurried and frantic as they fly. Bats have a slower, deeper wingbeat in comparison. Their wing shape changes more dramatically through each flap cycle, folding back on the upstroke then spreading wide on the downstroke. The flight of bats seems more leisurely with smooth banking turns.
Color
Chimney swifts have mostly dark brown plumage, a bit lighter on the throat. The only pale markings are small white patches on either side of the chin. Bats can be dark brown like swifts, but some species have gray, reddish or golden fur. Bats also often have paler faces than their bodies, whereas swifts have uniform coloration.
Trait | Chimney Swift | Bat |
---|---|---|
Size | 5 to 7 inches long | 2 to 13 inches long |
Wings | Long, curved and slender | Short and broad |
Flight Style | Stiff, shallow, rapid wingbeats | Slower, deeper flaps |
Body Shape | Cigar-shaped and streamlined | Flatter and more oblong |
Color | Uniformly dark brown | Can be brown, gray, reddish, or golden |
Habitat and Behavior
Chimney swifts and bats also differ in their preferred habitats and behavior patterns. Chimney swifts gravitate towards urban and suburban areas where there are brick chimneys for roosting and nesting. They mainly fly around higher altitudes hunting for flying insects. Bats may be found in both natural and human-made structures like caves, trees and attics. Most bat species hunt insects closer to the ground or beneath the canopy.
Roosting
Chimney swifts roost communally in unused chimneys and similar vertical hollow structures. They use their tiny feet to cling to the brick or masonry surfaces inside. At dusk, groups swarm and enter the chimney together. Bats may roost alone or in colonies in a variety of horizontal crevices and cavities. Many bat species hang from cave ceilings, tree branches, rafters and other surfaces in their roosts.
Perching
When chimney swifts do land to rest, they remain vertical. Since their feet cannot grasp branches, they rely on their sharp claws to cling to rough vertical surfaces like tree trunks. Bats use their more dexterous feet to hang upside-down from branches when perching.
Nesting
Chimney swifts construct nests of twigs glued together with saliva inside chimneys and hollow trees. The nests are bracket-shaped platforms stuck to the interior vertical surface. Bats do not build nests. Their young are born singly or in small litters and sheltered within the roost itself.
Feeding
Chimney swifts forage for insects exclusively on the wing. They feed higher up, often a hundred feet above the ground. Bats may hunt insects on the wing like swifts, but some also pluck insects from surfaces like flowers and trees. This allows them to feed closer to vegetation at lower altitudes than swifts.
Behavior | Chimney Swift | Bat |
---|---|---|
Roosting Sites | Inside open chimneys and hollow trees | Caves, buildings, trees, under bridges |
Roosting Position | Clings vertically to interior surfaces | Hangs upside-down from ceiling |
Nesting | Build twig nests glued to vertical surfaces | No true nest, young sheltered in roost |
Feeding | Catch insects in flight high up | Can feed lower down and glean from surfaces |
Appearance in Flight
The silhouettes of chimney swifts and bats in flight differ in more than just wing shape and wingbeat style. The flight profile of swifts shows their short, fan-shaped tail and cigar body tapering to a pointy tail. Bats have a more blunt, flat rump with a longer, more distinct tail. The short legs of a swift trail behind its body in flight. The longer legs of bats often extend farther behind them when in flight.
Flock Feeding
Swifts have a very social and communal nature. Outside the breeding season, they gather in large migrating flocks called kettles numbering in the thousands. Bats may emerge in numbers from roosts at dusk, but they disperse to hunt alone or in small groups rather than crowd together. So watch for tightly bunched flocks darting through the skies at dusk, a sign of swifts rather than bats.
Swift Screeching
The vocalizations of chimney swifts are higher-pitched and more piercing than bats. Swifts make a shrill twittering as well as a loud, descending “screech” in flight. This is thought to be a means of communication between flock members as they home in on roosts or feeding areas. Bats use ultrasonic echolocation calls inaudible to humans for orientation while flying.
Flight Characteristics | Chimney Swift | Bat |
---|---|---|
Body Profile | Cigar-shaped with short, fan-like tail | Flatter body and longer tail |
Legs | Short, trail behind body | Longer, may extend farther back |
Flying Style | Swift direct flying in large flocks | More maneuverable, solitary flier |
Vocalizations | High-pitched twittering and descending screech | Ultrasonic echolocation clicks |
Conclusion
Though telling them apart can be tricky at first, chimney swifts and bats have distinct differences that allow an observer to identify them correctly. Chimney swifts have uniform brown coloration, cigar-shaped bodies, stiff flight patterns and high-pitched flock vocalizations. Bats come in more varied colors and sizes, with longer tails and legs that show in flight. They fly more fluidly, hunt alone and make ultrasonic clicking sounds. Habitat and behavior also separate the two, with swifts preferring vertical structures and bats using more horizontal roosts. Watching closely for field marks and habits will reveal the true identity of these mysterious avian night flyers.