Commonly refers to an organisnm capable of flight using appendages called “wings” to generate lift. They act as a glider taking advantage of thermals to increase thier lift and minimise drag.
They are also usually very light, small and aerodynamic.
Some birds however don’
t have the advantage of flight. Some birds, for example the emu, are too
big and
heavy to
fly.
Also birds are NOT mammals, they are AVIANS.