Swifts are renowned for their sleek, scythe-shaped wings and a life spent almost entirely on the wing. They belong to the family Apodidae, a name derived from the Greek word for “without feet,” reflecting their unique, non-perching lifestyle. Some common swifts can remain continuously airborne for up to ten months, an adaptation that dictates a diet exclusively acquired in flight.
The Strict Diet of Aerial Plankton
The swift’s diet consists of “aerial plankton,” a collective term for the small arthropods that drift on air currents. Swifts are obligate aerial insectivores, meaning they must catch their minute prey, often just a few millimeters in size, while flying.
This airborne menu includes a diverse mix of:
- Small flies
- Aphids
- Beetles
- Gnats
- Mosquitoes
Spiders that travel by “ballooning” on silk strands are also a regular component. Swifts are opportunistic hunters, consuming hundreds of different species depending on location and weather. One swift can consume between 12,000 and 20,000 insects daily, illustrating the volume of prey required to sustain their high-energy flight.
Hunting and Hydration Mid-Air
Swifts possess a remarkably wide gape, allowing their mouths to open like a net to scoop up insects during pursuit. They are precise fliers, capable of executing complicated maneuvers to snatch individual insects or fly directly through a concentrated swarm.
Foraging efficiency is influenced by atmospheric conditions, as swifts utilize weather fronts and thermal updrafts where insects are naturally concentrated. They fly high into the air column, sometimes reaching thousands of meters, to locate dense patches of prey. The ability to glide using these air currents allows them to conserve energy while scanning for food.
Swifts manage their water intake by performing low, fast passes over bodies of water, such as lakes or rivers. They skim the surface momentarily to scoop up small amounts of water with their beak.
Specialized Feeding for Nestlings
The swifts’ aerial lifestyle dictates a unique method for provisioning their young inside the nest cavity. Unlike many birds that feed chicks one insect at a time, swifts collect thousands of individual prey items before returning. The parent bird stores these captured insects and spiders in a pouch located under the tongue and throat.
This mass of food is then compacted and bound together by sticky saliva to form a single, dense ball known as a bolus. A single bolus can contain up to 1,000 insects, and this compact package is delivered whole to the nestling. A parent swift must return multiple times a day to deliver these large packets of food, with each chick requiring up to 15 to 20 grams of insects daily to grow rapidly.