Q.What are the modifications observed in birds that help them to fly?

Birds are adapted for flight by streamlining, wings and feathers, light pneumatic bones, strong flight muscles on a keeled sternum, and air sacs for efficient respiration.

Flight adaptations in birds:

1. Streamlined body — the spindle-shaped body reduces air resistance during flight.
2. Forelimbs modified into wings — provide the surface and thrust needed for flying.
3. Feathers — the body is covered with feathers that provide the flight surface, insulation and reduce weight.
4. Light, hollow (pneumatic) bones — the bones are hollow and filled with air, making the skeleton light.
5. Strong flight muscles — well-developed pectoral (flight) muscles are attached to a large keeled sternum (breastbone) for powerful wing movements.
6. Air sacs — connected to the lungs, they supply extra oxygen and make the body lighter (double respiration). …

Pneumatic (air-filled) bones are a characteristic adaptation of birds, reducing skeletal weight to aid flight; among the options, only the sparrow (a bird) has this feature.

Birds (Class Aves) have a lightweight skeleton in which many bones -- particularly the long limb bones and parts of the skull -- are hollow and contain air cavities (pneumatic spaces) that connect to the respiratory air-sac system, significantly reducing body weight without sacrificing strength, an important adaptation for powered flight. Bats (option a), though also flying, are mammals with solid, dense bones (their flight adapta …