Poem found here: "Robins in Love" by William Logan
I don't know why I seek the shape of the poem when I reread it. In my mind, the three quatrains and a couplet automatically makes me assume there's something to do with a sonnet where there's a turn at the end. It's somewhat there, but it's the shifts in perspectives and tone throughout the poem that interest me.
Even with the first line, "Branched like an artery" is a somewhat cliche simile, but not so much at the same time. The visual is, but to start out with it without a noun places myself only knowing the other half of a comparison -- as though I'm expecting something different, but it doesn't happen, "the dying oak leafs out / with February month" exposition lines which shifts with the language of, "This is their layover month," a somewhat technical term of "layover" and then the excitement of, "down to the Keys and back. / True snowbirds!" foreshadows it's own shift in perspective.
A man with a .45 and a measured eye
could pick them off one by one,
or sketch them -- but why bother?
Imagination is enough,
So the first couplet (taken out of the stanza form) imagines a man killing the love birds and on the other sketching them -- from violence to art. However, the flippant tone of "but why bother?" brings cynicism to the line, "Imagination is enough" which the concept of not physically doing anything comes back not only with the continuing simile of Imagination, "like the bed you might / have shared with someone else" but also ties in with the couplet as well.
So the cynicism of inaction and imagination ends with the proclamation of, "They're chaste" -- from the bedroom to the birds. "chasing each other -- / one wing in the future, one in the past." The couplet has a grandiose feel to them because there was such feigned intimacy -- lovers or even further back through the eyes of a hunter/artist. The idea of metaphorical parts in both the past in the future based on the cynicism means a continuation of something chaste, something imaginative, never anything real.