![]() ![]() Most thrust is generated on the downstroke of flapping flight. ![]() These feathers are especially important for flapping flight, as they are the principal source of thrust, moving the bird forward through the air. Primaries are connected to the manus (the bird's "hand", composed of carpometacarpus and phalanges) these are the longest and narrowest of the remiges (particularly those attached to the manus), and they can be individually rotated. They are given different names depending on their position along the wing. ![]() Corresponding remiges on individual birds are symmetrical between the two wings, matching to a large extent in size and shape (except in the case of mutation or damage), though not necessarily in pattern. Remiges (from the Latin for "oarsman") are attached to the rear side of the wing the long calami, or quills, are deeply imbedded into the bones themselves. Different species have evolved different strategies for coping with this, ranging from dropping all their flight feathers at once (and thus becoming flightless for some relatively short period of time) to extending the moult over a period of several years. The moult of their flight feathers can cause serious problems for birds, as it can impair their ability to fly. Even flightless birds still retain flight feathers, though sometimes in radically modified forms. Tiny serrations on the leading edge of their remiges help owls to fly silently (and therefore hunt more successfully), while the extra-stiff rectrices of woodpeckers help them to brace against tree trunks as they hammer. In some species, these feathers have developed into long showy plumes used in visual courtship displays, while in others they create a sound during display flights. The flight feathers of some birds have evolved to perform additional functions, generally associated with territorial displays, courtship rituals or feeding methods. Their primary function is to aid in the generation of both thrust and lift, thereby enabling flight. 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.Flight feathers are the long, stiff, asymmetrically shaped, but symmetrically paired feathers on the wings or tail of a bird those on the wings are called remiges (singular remex) while those on the tail are called rectrices (singular rectrix). 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. The Alulae are particularly notable in peregrine falcons. 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. 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. Adult bald eagle landing, showing the alula in action ![]()
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