The Apodidae, or swifts, are highly aerial birds that resemble swallows but are not closely related. They belong to the order Apodiformes, which includes hummingbirds. Swifts and swallows show similarities due to convergent evolution, as both catch insects in flight. The name Apodidae comes from the Greek word ἄπους (ápous), meaning “footless,” referring to their small legs.
There are about 100 species of swifts, categorized into two subfamilies and four tribes:
- Cypseloidinae: Tribe Cypseloidini
- Apodinae: Tribe Collocaliini (swiftlets), Tribe Chaeturini (needletails), Tribe Apodini (typical swifts).
Appearance
They have a distinctive shape with short forked tails and long wings, which can give their flight a “flicking” appearance, unlike swallows. Swifts vary in size from the pygmy swiftlet at 5.4 g and 9 cm long to the purple needletail at 184 g and 25 cm long.
Swifts are among the fastest birds in level flight, with larger species like the white-throated needletail reaching speeds of up to 169 km/h (105 mph). The common swift can cruise at 31 meters per second (112 km/h; 70 mph) and may travel over 200,000 km in a year, totaling about two million kilometers in a lifetime. Their wingtip bones are proportionately longer than those of most birds, allowing for efficient maneuverability at various speeds. Swifts, like hummingbirds, can rotate their wings at the base, generating lift and thrust on both the upstroke and downstroke. Additionally, swiftlets have developed echolocation for navigating dark caves, with the Three-toed swiftlet using this ability even outside its roost at night.
Diet
All swifts primarily eat insects like dragonflies, flies, ants, and wasps, catching them in flight with their beaks. Some species, such as the chimney swift, hunt alongside other aerial insectivores like swallows.
Habitat
Swifts are found on all continents except Antarctica, and they do not inhabit the far north, large deserts, or many oceanic islands. Species in temperate regions are migratory, wintering in the tropics, and some can enter a state of torpor during short cold spells.
Behavior
Many species of swifts attach their nests to vertical surfaces using saliva, which is the primary ingredient in bird’s nest soup. Other swifts utilize small cavities in walls for nesting. Eggs hatch in 19 to 23 days, and young swifts leave the nest after six to eight weeks, with both parents participating in their care. Swifts typically have smaller egg clutches and longer incubation and fledging times compared to passerines with similar-sized eggs. Young swifts can grow heavier than their parents, can endure periods without food, and may delay feather growth if undernourished. While swifts have secure nesting sites, they face unreliable food sources, unlike passerines, which are vulnerable in their nests but generally have plentiful food.
