Bonta describes a tree that has lost its birds, and the poem shows how much a living thing depends on company. The opening comparisons set the tone: a book without vowels, a mind without focus, a heart without tides. Each one is something that still exists but can't work properly, and the tree is the same. It has leaves but never blooms, and even its underground dealings with fungi are "strictly economic," a dry exchange that produces nothing as delightful as a truffle.
The speaker sounds quietly mournful, though also wry. Calling the wind's playing "mechanical" suggests sound without feeling, a poor replacement for birdsong. The last lines are the saddest. In "bluest January" the tree "doesn't even remember / how to ache," so the loss has gone past pain into numbness. The mood is bare and wintry, and it hints that being able to feel the absence is better than forgetting what was missing.