Why do birds we try to save always die?

I once tried to save an injured crow
Who on realising my attempt
ran into the road.
Not one car
but two,
ran over it's body

I ran into the road,
and bought it back to safety
only to find it's head rolled back
in a way that made me queasy.
Completely lifeless.

And if there was any doubt,
a drunken passer-by stopped,
looked over my shoulder
and assured me with
'it's dead, that is, mate'.

I ran home with it anyway,
sobbing and guilty,
occasionally checking
if the dead bird,
was still dead.

I ran into my Mum's house
sobbing, 'I killed a bird!'
And on opening my coat
It jumped straight out,
and shat on the cushion's.

It died the next day.