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Swift (bird)

life science Maturity 7-9 Next article →

Swifts belong to the family Apodidae, a group of birds defined by their highly aerial lifestyle. The name Apodidae comes from the Greek word "ápous," which means "footless." This name refers to their very small and weak legs. While they look similar to swallows, they are not closely related to them. Instead, swifts belong to the order Apodiformes. This order also includes hummingbirds. The physical similarities between swifts and swallows are actually a result of convergent evolution. This happens when different species develop similar traits because they share similar lifestyles, such as catching insects while flying.

Dans l'ombre des dinosaures - Scaniacypselus - 02
Dans l'ombre des dinosaures - Scaniacypselus - 02

The flight mechanics of swifts are incredibly specialized for speed and control. They share a unique ability with hummingbirds to rotate their wings from the base. This rotation allows the wing to remain rigid and fully extended during flight. Because of this, they can derive power from both the upstroke and the downstroke. The downstroke produces both lift and thrust to move the bird forward. The upstroke is also productive; it generates lift equal to 60% of the lift from the downstroke. However, the upstroke also creates a negative thrust, or drag, that is 60% of the thrust produced during the downstroke. This arrangement likely helps the birds maintain high levels of maneuverability.

Mossy-nest Swiftlets (Aerodramus salangana natunae) on nest (15593076875)
Mossy-nest Swiftlets (Aerodramus salangana natunae) on nest (15593076875)

Swifts can also change the actual shape of their wings to fly more efficiently. They do this by altering the angle between the bones of their wingtips and their forelimbs. The wingtip bones of swiftlets are proportionately longer than those found in most other birds. This allows them to adjust the wing area for different speeds. There are approximately 100 species of swifts globally. These are generally organized into two subfamilies: Cypseloidinae and Apodinae. Within these, there are four distinct tribes. These include the Cypseloidini, the swiftlets (Collocaliini), the needletails (Chaeturini), and the typical swifts (Apodini).

Mossy-nest Swiftlets (Aerodramus salangana natunae) on nest (15593076875)
Mossy-nest Swiftlets (Aerodramus salangana natunae) on nest (15593076875)

The evolutionary history of these birds dates back to the Eocene epoch. During this time, the Apodiformes diversified, and the modern families were already present. Fossil evidence has been found throughout temperate Europe, ranging from Denmark to France. One ancient, swift-like genus is Scaniacypselus, which lived during the Early to Middle Eocene.

Dans l'ombre des dinosaures - Scaniacypselus - 02
Dans l'ombre des dinosaures - Scaniacypselus - 02

Another genus, Procypseloides, lived from the Late Eocene through the Early Oligocene and into the Early Miocene. Some scientists also suggest that a prehistoric genus called Primapus, found in the Early Eocene of England, might be a distant ancestor of the group.

In terms of physical scale, swifts vary significantly in size and weight. The pygmy swiftlet is extremely small, weighing only 5.4 grams. On the other end of the spectrum, the purple needletail is much larger and heavier. Some species are remarkably fast in level flight. The white-throated needletail has been reported to reach speeds of up to 160 km/h. Even the common swift is a powerful flyer, cruising at a maximum speed of 31 meters per second. The distances these birds travel are staggering. A common swift can cover at least 200,000 km in a single year. Over the course of its lifetime, a single bird may fly about two million kilometers.

Swifts have unique nesting and survival behaviors. Many species use their saliva as a glue to attach nests to vertical surfaces. The genus Aerodramus relies entirely on this salivary cement. This substance is the primary ingredient in bird's nest soup, a delicacy used in Chinese cooking for over 400 years. These nests are often built in caves and are composed of interwoven strands of saliva containing calcium, iron, potassium, and magnesium.

Mossy-nest Swiftlets (Aerodramus salangana natunae) on nest (15593076875)
Mossy-nest Swiftlets (Aerodramus salangana natunae) on nest (15593076875)

To navigate dark cave systems, some swiftlets have developed echolocation. The three-toed swiftlet has even been observed using this method to navigate at night outside of its roost.

Ecologically, swifts play a vital role by consuming various insects while in flight. Their diet includes dragonflies, flies, ants, aphids, wasps, bees, and even aerial spiders. While they are widespread, they are not found everywhere. They live on every continent except Antarctica, but they avoid the far north, large deserts, and many oceanic islands. Some species in temperate regions are highly migratory and spend winters in the tropics. To survive short periods of cold, some species can enter a state called torpor, which is similar to hibernation. While many species are stable, some, like the Guam swiftlet, are considered endangered due to various factors.

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