Swifts, belonging to the family Apodidae, are very aerial birds. They look similar to swallows but are not closely related. Swifts are in the order Apodiformes, which also includes hummingbirds. Treeswifts are related but belong to a different family called Hemiprocnidae. The similarities between swifts and swallows come from convergent evolution, meaning they have evolved similar traits because they live similar lifestyles, like catching insects while flying.
The name Apodidae comes from the Greek word ἄπους (ápous), which means “footless.” This refers to the small, weak legs of these birds. In the Middle Ages, people often depicted swifts without feet, as seen in the heraldic martlet.
Swifts can fly very fast. Larger species, such as the white-throated needletail, can reach speeds of up to 169 km/h (105 mph). The common swift can cruise at a maximum speed of 31 meters per second (112 km/h; 70 mph). In a year, a common swift can travel at least 200,000 km, and in its lifetime, about two million kilometers.
Swifts have long wingtip bones that help them change the shape and area of their wings for better flying efficiency and maneuverability. Like hummingbirds, they can rotate their wings from the base, keeping the wings rigid and fully extended. This allows them to generate lift and thrust on both the up and down strokes of their wings. The downstroke creates lift and thrust, while the upstroke creates negative thrust (drag) but also adds lift. This wing movement helps them control and maneuver in the air.
Cave swifts, also known as swiftlets, have developed echolocation to navigate dark caves where they nest. The Three-toed swiftlet can also use this ability at night outside its cave.
Swifts can be found on all continents except Antarctica. They do not live in very northern regions, large deserts, or many ocean islands. Swifts in temperate areas migrate to warmer regions in winter. Some can survive short cold spells by entering a state similar to hibernation.
Swifts have a distinct shape: a short forked tail and long wings that look like a crescent or boomerang. Their flight is marked by a unique “flicking” motion, different from swallows. They vary in size, from the pygmy swiftlet, which weighs 5.4 g and is 9 cm (3.5 in) long, to the purple needletail, which weighs 184 g (6.5 oz) and is 25 cm (9.8 in) long.
Many swift species build nests using their saliva to glue them to vertical surfaces. The genus Aerodramus relies only on saliva, used to make bird’s nest soup. Other swifts lay eggs in small cavities or holes in walls. Eggs hatch after 19 to 23 days, and young swifts leave the nest after another six to eight weeks. Both parents care for the young.
Swifts have smaller egg clutches and longer incubation and fledging times compared to similar-sized passerines. Young swifts can weigh more than their parents and can go without food for extended periods. When undernourished, they delay feather growth. Swifts have secure nest sites, but their food sources can be less reliable compared to passerines, which are vulnerable in their nests but usually find food easily.
All swifts eat insects, including dragonflies, flies, ants, aphids, wasps, and bees, as well as aerial spiders. They catch their prey in flight using their beaks. Some species, like the chimney swift, join mixed species flocks to hunt with other birds, such as swallows.
