Analysis of The Retrospective Bird

His caw is a cackle, his eye is dim,
And he mopes all day on the lowest limb;
Not a word says he, but he snaps his bill
And twitches his palsied head, as a quill,
The ultimate plume of his pride and hope,
Quits his now featherless nose-of-the-Pope,
Leaving that eminence brown and bare
Exposed to the Prince of the Power of the Air.
And he sits and he thinks: 'I'm an old, old man,
Mateless and chickless, the last of my clan,
But I'd give the half of the days gone by
To perch once more on the branches high,
And hear my great-grand-daddy's comical croaks
In authorized versions of _Bulletin_ jokes.'