1) The progressive development of the cerebral cortex and cerebellum led to more complex bird behavior
2) The emergence of a four-chambered heart with a complete separation of arterial and venous blood flow led to warm-bloodedness and intensive metabolism, as well as widespread settlement on Earth.
3) The formation of lungs densely penetrated with capillaries and the presence of air sacs made it possible to carry out ventilation during inhalation and exhalation (double breathing), which is an adaptation to flight
4) The forelegs are turned into wings.
5) The body is covered with feathers.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.