FLIGHT ADAPTATIONS

FLIGHT ADOPTATIONS


 Flight -Main mode of locomotion used by most of the world's bird species.
 Birds use flight
 to obtain prey on the wing,
 for foraging,
 to commute to feeding grounds and
 to migrate between the seasons.
 Also used by some species to display during the breeding season and
 to reach safe isolated places for nesting.
 The most obvious adaptation for flight is the wing.
 Forelimbs modified into the wings.
 Attached high up on the thorax.
 Equipped with special flight muscles and have been developed as instruments of propulsion through air.
 The elongated flight- feathers of wings are called the remiges ;help in flight and also provide wing shape.
 The expanded membranous part or vane of each remex forms a flexible and continuous surface for striking the air in flight.
 The flight- feathers of a wing form a broad surface for supporting the bird in air.
 The particular shape of the wing, with a thick strong leading edge, convex upper surface and concave lower surface, causes reduction in air pressure above and increase below, with minimum turbulence behind.
 This helps in driving the bird forwards and upwards during flight.
 Down feathers are soft and meant for insulation.
 Tail feathers are called rectrices which stretch sideways so that tail can be used like a rudder for turning and balancing.
WEIGHT REDUCING ADAPTATIONS
Thin hollow bones
Extensive bone fusion especially in the pelvic and pectoral regions
 Fusion of bones makes the skeleton light as well as strong.
 Coracoid, furcula, and scapula form a sturdy tripod -supports the wings and broad surfaces for the attachment of large flight muscles.
 The fusion of caudal bones into single pygostyle supports the tail feathers.
 Most of the skull bones are firmly fused together.
 The rigidity of the dorsal part of vertebral column due to fusion of vertebrae, provides a firm fuAdditional bony structures are fused into the pelvic girdle providing support to legs and rigidity.
 Ribs are mostly fused with the vertebrae, pectoral girdle and sternum.
 lcrum for the action of wings.
 Except in flightless birds, the sternum bears a large keel for anchoring of flight muscles.
 Bones in the forelimbs are highly modified for flight.
 Some bones fused or reduced.
 Fused clavicles form an elastic furcula that stores energy as it flexes during wing beats.
Extremely light feathers
 Provide lightweight wing, tail and body contouring.
Elimination of teeth and jaws
 Lack teeth or even a true jaw, instead having evolved a keratin beak - lightweight.
 Elimination of tail vertebrae and some digits
 To make it more efficient for flying
 Elimination of most skin glands
 A system of branching air sacs
 They act as balloons providing lightness to the body and reduce the specific gravity of the body as they contain warm air
 They act as accessory respiratory organs. They act as reservoir of air which is forced into lungs for ventilation during each expiration. Thus fresh air is available to lungs during inspiration as well as expiration.
 Oviparous external egg reproduction
 The expanded end of the oviduct receives the "naked" eggs.
 Fertilization takes place in the upper oviduct before albumin and shell are added.
 Special glands add albumin (white) to the egg as it passes down the oviduct.
 Farther down, the shell membrane, shell, and pigments are secreted.
 Eggs are laid outside the body- Less weight.
 The atrophy of gonads between breeding season
 Reproductive organs are small for the greater part of the year -decrease the birds’ weight for flight.
 Only during mating season do reproductive organs (Ovaries and testes) reach functional size.
 Only one ovary and oviduct
 In most females, the left ovary and oviduct develop and the right ovary and oviduct degenerate or is greatly reduced -decrease the weight of body.
 Female liver is displaced to the right to compensate for weight difference
 Small testes
 Males have small testes until the approach of the breeding season, when they may enlarge by 300 times.
 Males of most species lack a penis; mating involves bringing cloacal surfaces in contact.
 Rapid and efficient digestion minimizes weight of digesting food
 The digestive system is extremely efficient in absorbing energy from small amounts of food at a rapid rate.
 Because birds lack teeth they possess a gizzard.
 Composed of four muscular bands that act to rotate and crush food by shifting the food from one area to the next within the gizzard.
 Depending on the species, the gizzard may contain small pieces of grit or stone/pebbles that the bird Many birds possess a muscular pouch along the oesophagus called a crop.
 The crop functions to both soften food and regulate its flow through the system by storing it temporarily.
 The crop of pigeons, doves and some parrots, also produces a lipid / protein-rich "milk."
 has swallowed to aid in the grinding process.

POWER INCREASING ADAPTATIONS
Heat conserving plumage
 The light feathers hold a considerable blanket of enveloping air around the body and add much to its buoyancy.
 The non-conducting covering of feathers insulates the body perfectly.
Prevents loss of heat. Enables the bird to endure intense cold at high altitudes and also to maintain a constant body temperature