Since these species are not closely related to modern birds, either the alula evolved twice, or it did so more than 130 million years ago. The presence of an alula has been confirmed in several now- extinct ancient relatives of modern birds, including Eoalulavis hoyasi (an enantiornithine from the mid- Cretaceous, 115 mya) and the earlier Protopteryx fengningensis. Journal of Fluid Mechanics 768, 24 0260 V ideler, J.J., 2005. The Alulae are particularly notable in peregrine falcons. The inu ence of wing morphology on the three-d imensional ow patterns of a apping wing at bird scale. In falcons, the alula is more prominent, and provides a degree of control when the wing is cupped or tucked in a dive/stoop. During stretching of the wing down toward the ground, the alula is abducted from the wing and can be clearly viewed. Reading the various articles shows that the Alula wing was conceived by A.Holle and marketed in the UK by The Commercial Aeroplane Wing Syndicate. The tip of the alula forms a tiny vortex, acting similar to a vortex generator, that forces the airflow over the wing to better bind to it. This functions in the same way as the slats on the wing of an aircraft, allowing the wing to achieve a higher than normal angle of attack – and thus lift – without resulting in a stall. When flying at slow speeds or landing, the bird moves its alula slightly upwards and forward, which creates a small slot on the wing's leading edge. In most situations, the alula is held flush against the wing however, it can be manipulated. Alula size vary among birds, but how this variation is associated with the function of the alula remains unclear. Like the larger flight feathers found on the wing's trailing edge, these alula feathers are asymmetrical, with the shaft running closer to anterior edge.įunction Adult bald eagle landing, showing the alula in action The alula is a small structure present on the leading edge of bird wings and is known to enhance lift by creating a small vortex at its tip. There also are minor covert feathers overlying the flight feathers. The alula is the freely moving first digit, a bird's "thumb", and typically bears three to five small flight feathers, with the exact number depending on the species. The word is Latin and means "winglet" it is the diminutive of ala, meaning "wing". The alula / ˈ æ l j ʊ l ə/, or bastard wing, (plural alulae) is a small projection on the anterior edge of the wing of modern birds and a few non-avian dinosaurs. For other uses, see Alula (disambiguation). The joint at the alula root allows deflections both away from the wing leading-edge (forward) and away from the wing upper surface (upward). This article is about the anatomy of a bird's wing. The digit is covered with a set of 2 to 6 feathers to form the alula structure, also known as bastard wing.
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