The Caged Bird

I have a bird inside a cage
hanging by the window.
A trivial thing, this bird of mine,
for it will always sing.
All through the night and the day,
when it feels that breeze,
when it hears that rain,
when it knows that spring is here,
it will always sing.
This constant tune irks me
and i questioned one foul day:
"Why do you always sing?"
In one chirp it answered
then began again.
I wish that it would stop,
that horrid little thing.
But I couldn't let it go,
that bird that always sang,
until one fine day
when the sun shone bright.
It stood in it's cage
and sang a depressing tune.
I couldn't take it anymore
and opened the cage.
Oh! how that bird did sing!
It chirped and tweeted a song never uttered
and as it flew away
the quiet returned
and I smiled softly,
for now I knew
what had made the caged bird sing