Analysis of Not to sleep

Not to sleep all the night long, for pure joy,
Counting no sheep and careless of chimes
Welcoming the dawn confabulation
Of birch, her children, who discuss idly
Fanciful details of the promised coming -
Will she be wearing red, or russet, or blue,
Or pure white? - whatever she wears, glorious:
Not to sleep all the night long, for pure joy,
This is given to few but at last to me,
So that when 1 laugh and stretch and leap from bed
I shall glide downstairs, my feet brushing the carpet
In courtesy to civilized progression,
Though, did 1 wish, I could soar through the open window
And perch on a branch above, acceptable ally
Of the birds still alert, grumbling gently together.