could warble
Regular verb: warble - warbled- warbled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could warble
you could warble
he could warble
we could warble
you could warble
they could warble 	I could be warbling
you could be warbling
he could be warbling
we could be warbling
you could be warbling
they could be warbling	I could have warbled
you could have warbled
he could have warbled
we could have warbled
you could have warbled
they could have warbled	I could have been warbling
you could have been warbling
he could have been warbling
we could have been warbling
you could have been warbling
they could have been warbling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not warble
you could not warble
he could not warble
we could not warble
you could not warble
they could not warble 	I could not be warbling
you could not be warbling
he could not be warbling
we could not be warbling
you could not be warbling
they could not be warbling	I could not have warbled
you could not have warbled
he could not have warbled
we could not have warbled
you could not have warbled
they could not have warbled	I could not have been warbling
you could not have been warbling
he could not have been warbling
we could not have been warbling
you could not have been warbling
they could not have been warbling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I warble?
could you warble?
could he warble?
could we warble?
could you warble?
could they warble? 	could I be warbling?
could you be warbling?
could he be warbling?
could we be warbling?
could you be warbling?
could they be warbling? 	could I have warbled?
could you have warbled?
could he have warbled?
could we have warbled?
could you have warbled?
could they have warbled? 	could I have been warbling?
could you have been warbling?
could he have been warbling?
could we have been warbling?
could you have been warbling?
could they have been warbling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not warble?
could you not warble?
could he not warble?
could we not warble?
could you not warble?
could they not warble? 	could I not be warbling?
could you not be warbling?
could he not be warbling?
could we not be warbling?
could you not be warbling?
could they not be warbling? 	could I not have warbled?
could you not have warbled?
could he not have warbled?
could we not have warbled?
could you not have warbled?
could they not have warbled? 	could I not have been warbling?
could you not have been warbling?
could he not have been warbling?
could we not have been warbling?
could you not have been warbling?
could they not have been warbling?