YouTube accounted for nearly 5.5 billion streams, followed by Hulu, with 348.5 million and Yahoo, with 231.8 million. Fox Interactive Media surged ahead of Nickelodeon Kids and Family Network into fourth place, with 207.5 million streams -- up from 194.3 million in February.

Hulu -- now a solid if distant No. 2 to YouTube in online video -- continued its steady rise, increasing streams about 10% in March and adding about 600,000 unique viewers for a total of 9.5 million.

The March figures are a contrast to February, when total streams fell 15%, unique viewers declined 6%, and time per viewer dipped more than 5% to 169 minutes.

A seasonal surge in the online video audience tied to the NCAA Men's Basketball tournament likely helped boost overall viewership figures in March. CBS said unique visitors to its March Madness on Demand video service increased 60% over last year to 7.5 million, and total video and audio was up 75% to 8.6 million hours.

CBSSports.com alone generated 38.2 million streams last month and 3.3 unique video viewers -- up more than 1,200% and nearly 300%, respectively, from February. CBS also distributed its free March Madness offering across 200 sites including YouTube, Facebook and Yahoo.

Total video streams in March were up almost 40% from a year ago.

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