There is no such thing. Birds and mammals are distinct from one another.
There isn't a mammal-bird.
No. Whether it is tropical or not, no bird is a mammal.
There is no such thing. No bird is or ever was a mammal.
No. A budgerigar (budgie) or parakeet is a bird, not a mammal.
mammal
A mammal.
The only thing I can imagine you are asking about is a Bottlenose dolphin, and it is a mammal.
If a bird were to give birth, it would not be considered a bird, but a flying mammal with feathers.
A penguin is a bird or a vertibrate animal. Mammals are animals which only give birth to live young (with the sole exception of the platypus, which lays eggs).
Bird
Man is the only mammal that cannot fly but does. He uses aeroplanes. (And the penguin is not a mammal: it is a bird and some say it 'flies' underwater.)
The Kea is not a mammal. Its a bird.