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Swift flight

Swifts (Apus apus) are renowned for their extremely aerial life style. From the moment the young swift leaves the nest it sets out on a very long journey. It will spend almost its entire lifetime in the air, day and night. The only time swifts land for a considerable time period is during breeding. They forage on the wing, collect nest materials on the wing, sleep on the wing and perform yearly migrations between Europe and Africa. This extremely aerial lifestyle is naturally associated with a special aerodynamic design, which makes this bird interesting to study since it is potentially yet another important piece of the puzzle of understanding animal flight. In this project, we study the kinematics and the wake patterns of the flying swift in the wind tunnel.

Characteristic flight style

Swift in windtunnel

The results (so far) show that the flight manner, both regarding kinematics and wake structure, differs between swifts and other bird species studied before. The swift flies with relatively rigid wings, flexing them very little during the upstroke. This result in a different wake, with more or less constant shedding of vortices into the wake throughout the complete wingbeat, both down and up, which suggests that the change in forces generated is smooth.

The shape
 

Swift design

The swifts have long slender aft-swept wings and a stream-lined body. Furthermore, the wings have a very short arm section and a very long hand section compared with most other birds. Their feet are short and mostly used for clinging on to vertical surfaces.

Wake model of flapping flight

Swift cartoon

The simplified cartoon wake of the swift in flapping flight. It consists of a pair of wingtip vortices connected by spanwise vortices shed from the wing. During down stroke vortices of positive (counter-clockwise) circulation is shed and during up stroke vortices of negative (clockwise).

A swift in flight

Swift flight

A swift in flight keeps its head horizontally even during extreme maneuvers.

Page Manager:

Centre for Animal Movement Research
Evolutionary Ecology, Department of Biology
Ecology building S-223 62 Lund Sweden