How Can I Write This Poem?

In order to write this poem, I have to be ready
I can't start too soon, My left hand must become steady
I'll have to open my mind Wide and as free as a bird
but not just any:

I must be able to imagine cool, moist air tugging slightly on the wispy, sensitive tail-feathers of a peregrine falcon as she swoops towards her prey from a rocky cliff on the shores of the calm Hudson river with gentle waves lapping softly against the shoreline

My mind must be free
So I can find And so I can bind
Those words that make such lovely sounds To this humble sheet of paper.
Until then, I won't be
Ready.