No, a bird is not a mammal because it lays eggs, it metabolizes nutrients differently, they have a different digestive tract, and they have lighter bones.
Actually you should ignore the fact that a bird lays eggs. A platypus lays eggs and is a mammal, however, a bird is not a mammal because a mammal feeds its young milk.
No, a bird is not a mammal. Although both birds and mammals are warm-blooded vertebrates, mammals are in the class Mammalia and birds are in the class Aves. Differences between the two include the following: