Differentiate between birds and bats(mammal)?
| Birds | Mammals |
| Birds lay eggs. | Mammals give birth to young ones. |
| Mammary glands are absent. | Mammary glands are present in mammals through which young ones suck mother's milk. |
| Hollow bones are present in birds which aid in flying. | Hollow bones are absent in mammals. |
| Feathers are present in birds which provide passage for air and reduce friction. | Feathers are not present. |