what are differences between animals belonging to the aves group and those in the mammalia group?

In Aves, forelimbs are modified into wings for flight. In mammals, the forelimbs are variously adapted for walking, running, climbing, swimming etc.

Aves have pneumatic bones which are absent in mammals.

Birds excrete uric acid whereas mammals excrete urea.

Mammals show mammary glands which are absent in aves.

Aves are oviparous whereas mammals are viviparous.