Get out the microscope, because we’re going through this poem line-by-line.
Lines 19-20
Thy wee-bit housie, too, in ruin!
It's silly wa's the win's are strewin!
- The speaker exclaims that that mouse's little nest—her "wee bit housie"—is all in a ruin.
- Its weak little walls ("silly wa's") are being spread, or strewn, by the winds (the "win's").
- Note that Burns uses a lot of odd contractions—"walls" and "winds" aren't unfamiliar words, but they do look weird when he makes them into contractions like "wa's" and "win's" to mimic the sound of the spoken Scots dialect. (Check out "Sound Check" for more on that.)
Lines 21-24
An' naething, now, to big a new ane,
O' foggage green!
An' bleak December's winds ensuin,
Baith snell an' keen!
- The speaker adds, regretfully, that the mouse has nothing now to build a new one ("a new ane") with —it's no longer the right time of year for the mouse to find the right kind of second-growth green grass ("foggage green").
- Not only that, but it's almost December—and the bleak December winds, which will be both ("baith") biting ("snell") and sharp ("keen") are coming. Poor little mouse.