I could birdie you could birdie she could birdie we could birdie you could birdie they could birdie
V-ing form
I could be birdying you could be birdying she could be birdying we could be birdying you could be birdying they could be birdying
Perfect
I could have birdied you could have birdied she could have birdied we could have birdied you could have birdied they could have birdied
V-ing perfect
I could have been birdying you could have been birdying she could have been birdying we could have been birdying you could have been birdying they could have been birdying
Negation
Simple form
I couldn't birdie you couldn't birdie she couldn't birdie we couldn't birdie you couldn't birdie they couldn't birdie
V-ing form
I couldn't be birdying you couldn't be birdying she couldn't be birdying we couldn't be birdying you couldn't be birdying they couldn't be birdying
Perfect
I couldn't have birdied you couldn't have birdied she couldn't have birdied we couldn't have birdied you couldn't have birdied they couldn't have birdied
V-ing perfect
I couldn't have been birdying you couldn't have been birdying she couldn't have been birdying we couldn't have been birdying you couldn't have been birdying they couldn't have been birdying
Interrogative form
Simple form
could I birdie? could you birdie? could she birdie? could we birdie? could you birdie? could they birdie?
V-ing form
could I be birdying? could you be birdying? could she be birdying? could we be birdying? could you be birdying? could they be birdying?
Perfect
could I have birdied? could you have birdied? could she have birdied? could we have birdied? could you have birdied? could they have birdied?
V-ing perfect
could I have been birdying? could you have been birdying? could she have been birdying? could we have been birdying? could you have been birdying? could they have been birdying?
Interro-negative form
Simple form
couldn't I birdie? couldn't you birdie? couldn't she birdie? couldn't we birdie? couldn't you birdie? couldn't they birdie?
V-ing form
couldn't I be birdying? couldn't you be birdying? couldn't she be birdying? couldn't we be birdying? couldn't you be birdying? couldn't they be birdying?
Perfect
couldn't I have birdied? couldn't you have birdied? couldn't she have birdied? couldn't we have birdied? couldn't you have birdied? couldn't they have birdied?
V-ing perfect
couldn't I have been birdying? couldn't you have been birdying? couldn't she have been birdying? couldn't we have been birdying? couldn't you have been birdying? couldn't they have been birdying?