Question

humans give birth to young ones but birds lay eggs why

Answer 1

Birds don't give birth to live ones. They are warm-blooded and lay eggs. Their bodies are covered with feathers and they have wings. Feathers have three functions: flight, temperature  regulation and display. Most birds have hollow main bones with air sacs in them. This makes them lighter and makes flight easier.Birds are bipedal: they have two legs which are often covered with scales (small, flat plates which over-lap in the same way as feathers). They have a hard beak with no teeth.

Answer 2

all the creatures which have teeth they give birth and the rest lay eggs