There are two different and distinct tones used in "The Armadillo."
The tone of the first half of the poem could be described as admiring and awe-filled. The narrator speaks with great appreciation and wonder in regards to the fire balloons that he or she is looking at. They rise high into the night sky and become one with the stars and planets. It is a great image.
Once up against the sky it's hard
to tell them from the stars—
planets, that is—the tinted ones:
Venus going down, or Mars,
or the pale green one.
But the tone of the poem drastically shifts with the last line of the fifth stanza.
suddenly turning dangerous.
From that point forward, the tone is not admiring. The tone has become fearful, foreboding, and grave.
The balloons are no longer a thing of beauty. Instead they are destructive devices that destroy habitats and the animals that live there.
The flame ran down. We saw the pair
of owls who nest there flying up
and up, their whirling black-and-white
stained bright pink underneath, until
they shrieked up out of sight.
I would even support the idea that the tone of the final stanza is angry. The picture of a fist being clenched against the sky is a gesture of anger.
O falling fire and piercing cry
and panic, and a weak mailed fist
clenched ignorant against the sky!