Is a greater prairie chicken a mammal?

A greater prarie chicken is not a mammal for the fact that it lays eggs. Mammals are animals that give birth to live babies.

The above answer is only partly correct in that the greater prairie chicken (a grouse) is not a mammal, but not because it lays eggs, it is because it does not have mammary (milk) glands, sometimes called teats or tits. Some mammals do, in fact, lay eggs (such as the platypus), but they still feed their newborns from mammary glands. Therefore, not all mammals give birth to live babies (though most do), but all mammals have mammary glands, thus the name mammal.