Analysis of A Better Thing

I took it for a bird of prey that soared
High over ocean, battled mount, and plain;
'Twas but a bird-moth, which with limp horns gored
The invisibly obstructing window-pane!

Better than eagle, with far-towering nerve
But downward bent, greedy, marauding eye,
Guest of the flowers, thou art: unhurt they serve
Thee, little angel of a lower sky!