The vertebrate song

I lay eggs, what am I? 
A fish? 
No! I breathe through lungs, what am I?
A mammal?
No! I have feathers on my body.
Do you have wings and sometimes fly?
Yes - although I like to perch,
You may well see me in the sky.
You’re a bird!
Yes! 

I have scales, what am I?
A reptile?
No! I breathe through gills, what am I?
An amphibian?
No! I lay eggs only in water.
Are you aquatic?
So I’m told. You could call me ectothermic -
Like the water I am cold.
You’re a fish!
Yes! 

Fish, reptile or mammal?
Can you tell who is who?
Amphibian or bird?
Vertebrates are at the zoo! 

I have no scales, what am I?
A mammal?
No! I lay eggs, what am I?
A reptile?
No! My young are born in water,
When they grow they can breathe air.
Does your skin need to stay moist?
Yes, I think you’re nearly there.
An amphibian!
Yes! 

I have scales, what am I?
A fish?
No! I’m ectothermic, what am I?
An amphibian?
No! Sometimes I’ve claws upon my toes.
I always lay my eggs on land.
Oh you sound just like a lizard!
Yes, I think you understand!
You’re a reptile!
Yes! 

Fish, reptile or mammal?
Can you tell who is who?
Amphibian or bird?
Vertebrates are at the zoo! 

I’m endothermic, what am I?
A bird?
No! I can breathe air, what am I?
A reptile?
No! I have hair upon my body
And some glands through which I sweat.
Oh you sound a lot like me!
Let’s see then have you guessed it yet?
You’re a mammal!
Yes!