In light of the recent Yahoo-to-Bing organic search transition, marketers have been optimizing their sites for just two search engines, and the latest Nielsen data suggests that Bing-optimized sites may already be paying off. The research firm reports that Bing gained search ground, becoming the No. 2 search engine in August.

By Nielsen's measure, Bing accounted for 13.9 percent of consumers' queries last month, demonstrating a 2 percent increase over July 2010 and a 30 percent increase over August 2009. It seems Bing's gain was Yahoo's loss, as the latter dropped to third place with 13.1 percent of queries. Still, in light of the recent Bing-to-Yahoo search transition, which Brafton reported last month, the rise of Bing may be a win for both Microsoft and Yahoo.

Nielsen's report shows that Google maintains its top search market position in spite of Bing and Yahoo's shifts. The search giant accounted for 65.1 percent of all U.S. searches in August, and it has roughly maintained this market share both month-over-month and year-over-year.

Similarly, recent data from Hitwise shows that Bing and Yahoo – even combined – are not yet a force ready to reckon with Google. As Brafton reported last week, Hitwise says Google represented 71 percent of search market share in August.

Additionally, the Hitwise search rankings suggest that Yahoo maintained its second-place position last month, representing 14.28 percent of queries compared to Bing's 9.87 percent. Still, this data shows that Bing's share jumped by a small margin in the week following Bing and Yahoo's combined search.

It will be interesting to see how comScore's August 2010 search data compares to Nielsen and Hitwise search rankings. ComScore's July metrics indicate Yahoo was six points ahead of Bing before the transition, while Google – not surprisingly – came out on top.