The key thing to watch with bond funds is duration, which tells the impact of a change in interest rates. The short term (2.8 duration), intermediate term (6.5 duration) and long term (16.2 duration) have different risks when interest rates rise. You can find that data on Vanguard's website, and the performance of Vanguard ETFs on etfdb (Vanguard doesn't update it very often).
Using treasuries from Jan 4 to Feb 18:
https://www.treasury.gov/resource-center/data-chart-center/interest-rates/pages/TextView.aspx?data=yieldYear&year=2021(feb 18) 3 yr treasury, 0.16% to 0.21%, 0.05% x -1 x 2.8 = -0.14% (actual -0.18%)
(feb 19) 3 yr treasury, 0.16% to 0.22%, 0.06% x -1 x 2.8 = -0.17% (actual -0.18%)
=> Not sure why Feb 19 is more accurate here, while Feb 18 is for the others...
7 yr treasury, 0.64% to 0.94%, 0.30% x -1 x 6.5 = -1.95% (actual -1.84%)
10 yr treasury, 0.93% to 1.29% (prorating roughly, 1/3rd of long term)
20 yr treasury, 1.46% to 1.91% (prorating roughly, 2/3rd of long term)
Long term (0.36 / 3 = 0.12) + (0.45 * 2 / 3 = 0.30) = 0.42 x -1 x 16.2 = -6.8%
(actual BLV performance was -6.7%)
Notice that duration was a good estimate of the drop in each bond fund, and that longer term bonds got hit from two directions: larger duration, and bigger increases in yields. That's why losses in long term bonds were 37x higher than short term bonds, despite their durations being 6x apart.
I generally prefer shorter term bonds, and take my risk in equities.