I could birdie you could birdie he could birdie we could birdie you could birdie they could birdie
V-ing form
I could be birdying you could be birdying he could be birdying we could be birdying you could be birdying they could be birdying
Perfect
I could have birdied you could have birdied he 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 he 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 he 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 he 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 he 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 he 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 he birdie? could we birdie? could you birdie? could they birdie?
V-ing form
could I be birdying? could you be birdying? could he be birdying? could we be birdying? could you be birdying? could they be birdying?
Perfect
could I have birdied? could you have birdied? could he 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 he 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 he 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 he 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 he 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 he have been birdying? couldn't we have been birdying? couldn't you have been birdying? couldn't they have been birdying?