What are the adaptations observed in birds that help them in flight?

(N/A) The adaptations in birds that facilitate flight are as follows:
$1$. The jaws are modified into a beak.
$2$. The forelimbs are modified into wings.
$3$. The endoskeleton is fully ossified (bony),and the long bones are hollow with air cavities,known as pneumatic bones.
$4$. They are homeothermic (warm-blooded) animals,and feathers act as insulators to maintain body temperature.
$5$. The presence of air sacs connected to the lungs supplements respiration and reduces body weight,aiding in flight.