Ratings Chart Attack!

Network viewership was off across the board Thursday, the first night of the May sweep, with many shows posting their worst performances ever, including 10 p.m. newcomers “Southland” and “Harper’s Island.”

ABC won the night, with the network’s “Grey’s Anatomy” the No. 1 show, scoring a 4.9 rating/13 share among adults 18-49 and 13.2 million viewers, according to preliminary Nielsen figures. Last night’s episode, the first original in about a month, was off 13% in the demo from that episode and scoring the lowest rating ever for an original. “Grey’s” still provided a solid lead-in for a new “Private Practice,” which scored a 3.4/10 (9.2 million) in the 10 p.m. hour. “Practice” remained flat from its last original episode last month and won its hour against new series “Harper’s Island” and “Southland.” The network aired a “Grey’s” repeat at 8 p.m.

All three original programs on CBS came in with series lows. “Survivor: Tocantins” (3.5/11, 11.4 million) saw the series’ lowest original performance ever, excluding Thanksgiving and clip shows, as did “CSI” (3.6/9, 14.5 million), which posted a 5% decrease from last week. In its third week out, “Harper’s Island” (2.0/6, 7.5 million) continued its downward trend, falling 9% from last week.

Several of the male-skewing shows were affected not only by increased competition from other broadcast networks, but also by NBA basketball coverage on TNT.

On NBC, “My Name Is Earl” (2.2/7, 5.5 million) was flat with last week, while “Parks and Recreation” (2.3/7, 5.2 million) posted an 8% loss from last week. “The Office” (3.7/10, 7.2 million) posted the lowest rating for an original episode in its regular timeslot this season, while “30 Rock” (3.1/5, 6.3 million) slipped 11% from the week before but increased 15% over last year in the same time period. At 10 p.m., “Southland” (2.5/7, 8 million) scored its lowest rating after three weeks, and posted a much bigger loss between its second and third weeks than from first to second (17% vs. 6%).

Fox aired original episodes of “Bones” (2.2/7, 8.2 million) and “Hell’s Kitchen” (3.0/8, 6.8 million), both down from their previous week’s performance (12% and 14%, respectively).

The CW aired new episodes of “Smallville” (1.3/4, 3.1 million) and “Supernatural” (1.1/3, 2.8 million), and both saw decreases from their last original episodes (24% and 27%, respectively). The network averaged a 1.1/3 among women 18-34.

For the night: ABC was first (3.2/9, 9.2 million), followed by CBS (3.1/9, 11.1 million), NBC (2.7/8, 6.7 million), Fox (2.6/7, 7.5 million) and The CW (1.2/3, 2.9 million).