The only real surprise here is the big jump for WBZ-AM and WBUR. No idea where that came from. Maybe the weather, but that wouldn't account for WGBH-FM failing to also benefit.
KISS 108 is usually on top, except for the holiday period when WMJX rules. WMJX is uniquely well placed to take advantage of the holidays; most stations would alienate their core audience if they flipped to holiday music, but WMJX listeners are happy to go along for the Christmas sleigh ride and stay with the station on December 26.
Sports talk is in the off-season doldrums: the Patriots are done, the Red Sox haven't started yet, and the Celtics and Bruins only generate intense interest during the playoffs. (During the ratings period, not when I'm writing this!) In another city March Madness would be a big deal, but Boston is a PROFESSIONAL sports town and not a college sports town. Expect to see an uptick for WBZ-FM and WEEI-FM in April with the Sox season starting, plus the NBA and NHL playoffs and the NFL draft all generating interest.
It looks like WBOS has bottomed out for now, with stable ratings for the past four periods. The numbers are still pitiful; what with having the alternative format pretty much to themselves in Boston (the current chart lists WXRV-FM as alternative but they're really an AAA station) they should be able to pull at least a 3, as they did in the period after the demise of WFNX and before the current management made the station worse.
Speaking of WXRV, they're doing remarkably well, especially given their marginal signal in the city of Boston. I think they have pulled away some of the audience that would be listening to WBOS if that station's execution were better.
A big drop for WKAF in this chart. Might just be a statistical anomaly, or it could be the effect of returning to a normal commercial load after a more limited commercial schedule during their period of building an audience for the new format.