A Blackbirds lament

[Achebe]

The opening is animated, the middle contemplative, and the ending wistful. It's just as it should be.
Minor nit: the punctuation, particularly the commas, is/are erratic. 
Some other observations  inline below.
Overall, one of your best (at least in the last six months or so)

The pellet hit your breast
and took my breath,
my mind followed a rising panic
of realisation, I had taken a life.

I had laid the breadcrumbs
hid behind the garden wall
waited in silence as you landed,
lined the sight, squeezed the trigger
it was all my responsibility. ... lose the 'it was'?

Your body was still warm
as I tried to revive you
soft like you were filled with water. ... this is a beautiful line
The colour of your beak
the clarity of your eyes
the perfect design of your feathers
all wasted by me.
I buried you in the garden
and made promises
I have kept. ... though heard a million times in one form or another, the above three lines are perfect

The following year I saved
a fledgling thrush
from the mouth of a cat,
raised it on worms,
set it free when the weather
turned warm,
gave it back your life. ... this line is slightly irritating - very slightly - because it labours the obvious. The 'your life' is fine, but 'gave it back' is too, too, bloody direct, and mars the subtle suggestion of the preceding lines. 

He only visited the garden
a few times,
but I kept looking.
Maybe he made new friends
or maybe the other birds told him
what I was really like. ... great ending