A walk in late winter becomes a series of small, strange discoveries. The speaker notices holes in a maple trunk and imagines a Roman soldier's lance, a leap that turns an ordinary tree into something like a battlefield relic. The holes are probably the work of a bird, though the poem never says so outright; it lets the violent image hang there.
Then the focus shifts to the speaker's own footing. The ice and sleet look like solid ground, but they haven't set, so each step plunges through. There's a quiet humor in "I keep breaking through," but also a sense of being slightly out of place, unable to trust the surface. The phrase also hints at a wider idea of breaking through to something new.
The cardinals end the poem on a playful note. Pecking at the road, they gather bits of grit that look like "faux teeth," which they treat as sacred objects. The mood is wry, watchful, and a little mythic: ordinary winter things become ancient and strange.