Birds and insects differ because they have different bodies. A bird is considered to be vertebrae. The wings of the bird are made out of feathers, and it flies like an airplane. Insect wings are made from stiff cells, they are very delicate, and they operate like a helicopter. Birdwings are bone and muscle limbs covered with feathers. Birds are graceful, and they can soar in the air without having to expend too much energy.
When an insect is flying, it has to create an enormous amount of energy to flap its wings. They have to catch air and force it down, which creates an equal and opposite reaction, which pushes them up. For both the bird and the insect, the taking off part is the most energy-intensive part of the flight.