The alula, or bastard wing, is a small, feathered projection on the anterior edge of the wing of modern birds. It is actually the thumb of the bird, and has been modified into an aerodynamical control device not too dissimilar from the forward slat on an airplane wing. Usually flush against the wing, the alula may be moved to modify the shape of the wing or provide a slat for direction of airflow, often to avoid stalling while landing. It has been found in all modern birds since Eoalulavis hoyasi, a primitive bird from the mid-Cretaceous, 115 million years ago. Two feathers A white feather Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds. ... A Laughing Gull on the beach in Atlantic City. ... Orders Many - see section below. ... In human anatomy, the thumb is the first digit on a hand. ... This article is about the branch of Physics. ... Slats are small aerodynamic surfaces on the leading edge of an airplane wing which, when deployed, allow the wing to operate at a higher angle of attack. ... In aerodynamics, a stall is a condition in which an excessive angle of attack causes loss of lift due to disruption of airflow. ... Landing is the last part of a flight, where a flying animal or aircraft returns to the ground. ... The Cretaceous period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic period, about 146 million years ago (Ma), to the beginning of the Paleocene epoch of the Tertiary period (65. ...

See also

• Bird flight