when a bird flaps its wings

Bounding flight edit

Small birds frequently use a technique called alternating short bursts of flapping with intervals where the wings are folded against the body to fly long distances. This type of flying pattern is called “bounding” or “flap-bounding.” [6] The bird’s trajectory is mostly ballistic with a tiny amount of body lift when its wings are folded. [2] By lowering aerodynamic drag during the ballistic portion of the trajectory, the flight pattern is thought to reduce the energy needed[7] and improve muscle usage efficiency. [8][9].

From the ground up edit

Numerous coelurosaurian dinosaurs, including the early tyrannosauroid Dilong, have been found to have feathers. [42] Nearly all palaeontologists classify modern birds as coelurosaurs. Feathers may have originally served as thermal insulation and in competitive displays [43]. According to the most widely accepted version of the “from the ground up” theory, birds’ progenitors were tiny ground-running predators (similar to roadrunners) that used their forelimbs for balance when pursuing prey. Later, the forelimbs and feathers evolved to enable gliding and eventually powered flight. [44] According to another “ground upwards” theory, fighting and competitive displays drove the evolution of flight at first. Displays necessitated longer feathers and stronger forelimbs; many modern birds use their wings as weapons, and downward blows function similarly to flapping flight. [45] Many Archaeopteryx fossils are found in marine sediments, and it has been hypothesized that the birds’ wings enabled them to run over water like common basilisks. [46].

The “from the ground up” theory has been under attack recently, primarily in an effort to disprove the premise that birds are evolved coelurosaurian dinosaurs. The most powerful attacks stem from analyses of embryology that conclude that the digits 2, 3, and 4 on a bird’s wings (which in humans correspond to the index, middle, and ring fingers) form the alula, which the bird uses to avoid stalling during low-speed flight, such as landing. In contrast, the digits 1, 2, and 3 on a coelurosaur’s hands (which in humans correspond to the thumb and first two fingers) [47] Nevertheless, these embryological analyses were quickly contested on the embryological grounds that, in clades that have lost some digits during their evolutionary history, the “hand” frequently develops differently, and that, as a result, the hands of birds do develop from digits 1, 2, and 3. [48][49][50].

Wings editMain article:

The birds forelimbs (the wings) are the key to flight. The humerus, ulna, and radius are the three limb bones that make up the central vane of each wing, which is used to catch wind. Once consisting of five digits, the hand, or manus, is reduced to three (digits II, III, and IV or I, II, III depending on the plan used[19]). The hand acts as an anchor for the primaries, one of the two groups of flight feathers that give wings their airfoil shape. The secondaries are the other set of flight feathers located on the ulna behind the carpal joint. There are three sets of what are referred to as coverts, the remaining feathers on the wing. The wing sometimes has vestigial claws. Most species lose these by the time they are adults (like the highly visible ones used by hoatzin chicks for active climbing), but some species, like the secretarybird, screamers, finfoots, ostriches, several swifts, and many others, retain their claws as an adult.

The locking mechanisms in albatrosses’ wing joints lessen the strain on their muscles when they soar. [20].

Even within a species wing morphology may differ. For instance, it has been discovered that adult European Turtle Doves have longer, more rounded wings than juveniles. This suggests that selection for flight maneuverability becomes more crucial after the juveniles’ initial molt, and juvenile wing morphology facilitates the birds’ first migrations. [21].

When female birds are exposed to predators during ovulation, their offspring grow their wings more quickly than those of females who are not exposed to predators. Their wings are also longer. Both adaptations may make them better at avoiding avian predators. [22].