Description from Knitty.com:

The socks are worked from the top down and hemmed, one of my favorite ways to start top-down socks. Although kind of a fiddly technique, there is something very satisfying about making socks without any cast on edge to bind at the top. The Thunderbird pattern causes a subtle slouch effect because of the natural pleating of the knit/purl pattern. The garter rib stitch used on the leg and foot is soft but form fitting, resulting in very comfortable, squishy socks.