Spring is in the air, and auds are flocking to unscripted fare in primetime.

Fox’s “American Idol” dominated again last week, but ABC’s “The Bachelor” cracked the top five in program rankings with its finale. And on Monday of the current week, the Alphabet’s “Dancing With the Stars” opened its 12th season impressively.

Overall, 10 of last week’s top 15 programs in adults 18-49 were reality shows airing on ABC, CBS, NBC, Fox and MTV.

The week also included the return of another unscripted spring tradition: college basketball’s March Madness tournament. For the opening week, CBS and Turner cablers TBS, TNT and TruTV combined to average 8.4 million viewers — up 14% from last year’s 7.4 million viewers when CBS went at it alone. (The Eye, though, was down sharply in primetime on both Thursday and Friday vs. last year when it aired the games entirely on its network.)

The most-watched game on Thursday (when all four nets aired games in primetime) was the BYU-Wofford contest on CBS (4.67 million), while the top draw on cable was UCLA-Michigan State on TBS (2.44 million). On Friday, CBS again aired the most-watched game (4.45 million for Washington-Georgia), with TBS topping the cablers (2.50m for Kansas-Boston U.).

As action moved into the third round, the cablers gained auds, led by a pair of Saturday games on TBS — Pittsburgh-Butler (3.56m) and Connecticut-Cincinnati (3.46m) — and Sunday’s evening contests on TNT — Texas-Arizona and Kansas-Illinois (both 4.41m).

Overall for the week of March 14-21, according to Nielsen, Fox cruised to victory in adults 18-49 with a 3.2 rating/10 share, with CBS (2.0/6) edging out ABC (1.9/6) for second, and Univision and NBC tying for fourth (1.5/5). Fox also won again in adults 25-54 (3.7/10) and total viewers (9.4 million).

With a fourth straight weekly victory in 25-54, Fox has tied CBS for the season lead in the demo, and it now appears — especially with “American Idol” holding up so well — that it will finish on top.

Looking at last week’s action, “Idol” may have hit season lows during the first week of Daylight Saving Time, but its segs on Wednesday (7.6/22, 22.58m) and Thursday (5.7/19, 19.57m) were still easily the week’s top shows in 18-49.

Also in the top 20 among adults 18-49 were “Glee” (4.2/13, 11.15m), the week’s No. 1 scripted skein, as well as “House” (3.5/10, 10.41m), “Bones” (3.3/10, 11.61m) and Sunday comedies “Family Guy” (3.3/9, 6.55m) and “The Cleveland Show” (2.6/7, 5.45m).

CBS was led by “Criminal Minds” (3.6/10 in 18-49, 13.73m), the week’s No. 1 drama in 18-49 and the top scripted program in adults 25-54 (4.7/11) and total viewers. Also ranking in the top 15 were the net’s reality trio: “Survivor” (3.2/10, 10.73m), “The Amazing Race” (2.8/8, 10.13m) and “Undercover Boss” (2.8/7, 11.70m).

At ABC, “The Bachelor” wrapped its season with highs (4.7/13 in 18-49, 13.88m), and followed it up with similar scores for its “After the Final Rose” spec (4.7/13, 13.96m). And on Monday of this week, “Dancing With the Stars” kicked off its spring season with the top scores for any regular series in 2011 (5.3/15 in 18-49, 22.66m).

Soph sci-fi drama “V” edged up with its season finale Tuesday (2.9/5, 5.51m) and is on the bubble for next season, while rookie “Detroit 1-8-7” didn’t do itself any favors by scoring meekly on Tuesday (1.2/4, 5.64m) and with its special Sunday finale (1.1/3, 4.65m). Also struggling are Wednesday rookies “Mr. Sunshine” (1.8/5, 4.54m) and “Off the Map” (1.3/4, 4.21m).

NBC was paced by two-hour reality staples “Celebrity Apprentice” (2.8/8, 8.17m) and “The Biggest Loser” (2.7/8, 8.00m), but its other unscripted skeins — “Minute to Win It” (1.0/3, 3.31m) and “America’s Next Great Restaurant” (1.2/4, 3.77m) — are struggling in their crowded reality timeslots.

In a big week for news, Fox News Channel (2.11 million) stood as the third most-watched cable net in primetime (behind USA and Disney Channel), with CNN (1.45 million) moving up to 10th place. CNN was the top newsie in primetime among adults 25-54 (585,000), edging out FNC (561,000) and more than doubling MSNBC (262,000).

USA led all cablers in total viewers as well as adults 18-49 and 25-54, though basketball-boosted TBS and TNT moved up to second and third, respectively, in both of the demos. “WWE Raw” did most of the demo damage for USA (2.3/7 in 18-49, 5.87m for its 10 p.m. hour).

MTV had a solid week as “Jersey Shore” was cable’s No. 1 show in most categories (3.4/10 in 18-49, 6.60m) and “Teen Mom” (2.5/7, 4.52m) hit a season high and was cable’s No. 2 show in 18-49. And in its second week, the 25th season of “The Real World” (1.3/4, 2.16m) continues to outperform recent editions.

Comedy Central had a big Tuesday with “Tosh.0” (1.9/6, 3.33m), followed by the “Comedy Central Roast of Donald Trump” (1.9/7, 3.48m), which led its timeslot in men 18-49 (2.6/10).

And at HBO, Sunday’s series finale of “Big Love” didn’t spike (0.7/2 in 18-49, 1.57m).