Remember when Thursday was the marquee night for broadcast networks when they were doing double-digit demo ratings with the likes of ER, Grey’s Anatomy and CSI? Well, those days are long gone with a 3 demo rating now the high-water mark. It was another brutal Thursday for the broadcasters last night with a number of series hitting new lows. CBS’ veteran CSI (2.8 rating/8 share in adults 18-49), which had been struggling this season, hit an all-time low, even without an original Grey’s running against it. (ABC tried out Grey’s spinoff Private Practice in the 9 PM slot , which drew a 2.3/6, down 10% from its last original at 10 PM for a season low.)

Even CBS’ Survivor (3.6/11), which has emerged as the ratings leader on the night, tied its lowest-rated telecast this cycle (but still ranked as the top program of the night in the demo, followed by NBC’s The Office (3.3/9), down 6% from its last original and CBS’ The Mentalist (3.0/8), down 14%.

NBC aired Community (1.7/5) at 8 PM, which hit an all-time low, down 19% from its last original, new 30 Rock at 8:30 PM (1.9/6), an all-time Thursday low, down 5% from the last Parks & Recreation in the time slot, The Office (3.3/9) at 9 PM, a season low, another 30 Rock episode (2.5/7) at 9:30 PM, which was down 14% from the last original in the time slot, and The Marriage Ref (1.9/5), which wrapped the night with a series low, down 10% from the last original.

Fox’s Bones (2.5/7) and Fringe (2.1/6) were down 14% and 16%, respectively, from last week. There was little good news to go around: ABC’s bubble freshman series Flash Forward (1.6/5, 5.6 million), grew week-to-week by 12% in total viewers and by 14% in adults 18-49. And at the CW, Vampire Diaries was up from last week in total viewers (3.3 million), while Supernatural hit its best demo ratings in months. For those keeping score, CBS won the night in both 18-49 and total viewers.

UPDATE: OK, I have to confess I had no idea there was an NFL draft  on TV last night, but based on the response from male readers, it seems like that’s what many of them were watching last night. That could explain at least some of the ratings erosion. And for the gals, there was the season finale of Project Runway. On a separate note, NBC is giving its bubble medical drama Mercy a boost next week, moving the struggling freshman from 8PM to 9PM, with reality series Minute To Win It as a lead-in. Mercy‘s performance in the upgraded time slot will certainly influence the network’s decision whether to renew the show for another season.