BOSTON/NEW YORK, Aug 14 (Reuters) - Top U.S. hedge fund management firms, including Jana Partners and Blue Ridge Capital, placed new bets on such companies such as FitBit Inc and Precision Castparts Corp. Fitbit, which sells the Fitbit Surge bracelet and other wearable fitness-tracking devices, went public in mid-June, and Warren Buffett's Berkshire Hathaway Inc said this week it would buy Precision Castparts. The actions were revealed in quarterly disclosures of hedge fund manager stock holdings, known as 13F filings, with the U.S. Securities and Exchange Commission. They are of great interest to investors wanting to know what savvy traders are selling and buying. The disclosures are backward-looking and come out 45 days after the end of each quarter. Still, the filings offer a glimpse into what hedge fund managers saw as... More