Stanza 4 Summary

Get out the microscope, because we’re going through this poem line-by-line.

on its string. Birdlike, the almanac
hovers half open above the child,

The almanac is hanging on a string on a hook or nail in the wall. It's partially open (because it's hanging), so it looks like a bird. What a simile.
In these lines, we've got another example of mixing indoor and outdoor imagery, as an indoor object is being described as an outdoor creature. This is also another example of an inanimate object being described as something that is alive and animate (as in, a bird).
The poem is beginning to feel very imaginative, don't you think? Bishop has a knack for bringing life to what might otherwise be a pretty stock and standard domestic scene.
The fact that the almanac is "half open" somehow makes us think that it is inviting the child to peek inside or that it hasn't finished telling jokes or foretelling quite yet. We get the sense that the almanac hasn't really been put away—it might become important again later.

hovers above the old grandmother
and her teacup full of dark brown tears.

The almanac also hangs over the grandmother and her tea, just as it hovered over the child. Because the speaker uses it twice, the word "hovers" jumps out at us here. Why doesn't our speaker describe the almanac as "hanging" or "resting?" The fact that it "hovers" makes us think of a helicopter or bee that momentarily pauses over something, ready to fly off at a moment's notice. The word "hovers" makes us feel like the almanac is in the middle of something—it's in suspended animation.
The fact that our speaker is careful to mention that the almanac hovers over both the child and grandmother makes us think that this book holds power over both of them, but maybe in different ways. If it hovers over the grandmother, it must be pretty high up on the wall, or she must be pretty short.
Bishop writes that the cup is full of tears, but we're thinking she really means tea—she's just using a metaphor. After all, since when are tears brown?
Still, the metaphor itself hones in on whatever sadness the grandmother was feeling before. Maybe now she's crying into her teacup, making for some salty Earl Grey.
It seems like even though they are sitting together in the kitchen, the grandmother and the grandchild are starting to go into their own private worlds right now.
The grandmother's sadness is something this kiddo has no access to, and whatever the kid's thinking, we're betting the grandmother doesn't have a clue.

She shivers and says she thinks the house
feels chilly, and puts more wood on the stove.

The grandmother is getting cold, so she puts more wood on the stove to keep the fire hot.
The stove in this poem is a wood-burning stove used to both cook and heat the house.
Why doesn't our speaker say "she shivers and says the house/ feels chilly…" instead of she shivers and says she thinks the house/ feels chilly?" What is significant about the way in which she thinks the house is cold? This word choice makes us feel that the house might not be cold, but that she needs an excuse to do something and to move about, maybe to distract her from those tears in her teacup.
It's September, at the turn of the season, and we start to get a sense of something spooky, or dark is going to happen—maybe all the tears so far are making us think gloomy thoughts.