NEW YORK (TheStreet) -- Warren Buffett's biggest maneuver in the first quarter of the year was, without a doubt, investing $10 billion alongside 3G Capital to orchestrate the merger of H.J. Heinz Co. and Kraft Foods Group (KRFT) .

Another of major move for Buffett? Increasing by nearly 50% his stake in Precision Castparts (PCP) , a manufacturer of metal components and products that you probably never heard of. The stock has declined 9% thus far for the year. It's rare that the Oracle of Omaha leaves market observers scratching their heads.

Buffett is not the only billionaire investor to have made a move that some might find surprising in the first quarter of 2015.

The latest round of 13F filings, required of all money managers overseeing more than $100 million in equities traded on U.S. exchanges, revealed some rather intriguing buys and sells.

While some big-name investors cashed in on major long positions, others poured money into areas that might seem a bit out of character. Here's a look at some of the most interesting billionaire maneuvers of the first quarter:

David Tepper Cashes In on American Airlines

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David Tepper dove in on American Airlines Group (AAL) - Get Reportin the wake of its 2013 $17 billion merger with U.S. Airways and remained bullish on the stock throughout 2014.

He first disclosed his American Airlines shares in the holdings report corresponding to 2013's fourth quarter. The stock became his top public equity pick in the second quarter of 2014, when he reported 11.7 million shares valued at more than $500 million. By the end of last year's fourth quarter, though, the billionaire had scaled back, reducing his position to 4.3 million shares valued at $233.6 million.

The Appaloosa Management founder's latest disclosure revealed that in the first quarter of the year, he cashed out entirely.

American Airlines proved a stellar investment for Tepper, as the stock climbed 115% in 2014. At a recent investor conference, American Airlines CFO Derek Kerr indicated that management is just getting started with the changes it plans to make in its operations. David Tepper appears to have gotten enough out of the company already -- at least for now.

Julian Robertson Likes China's Amazon -- But Not Amazon Itself

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Often referred to as the Amazon of China, (JD) - Get Report has grabbed the attention of many investors since going public last year. Since its IPO, the stock of the e-commerce giant has climbed about 60%.

Julian Robertson jumped on the bandwagon during the first quarter of the year, picking up 427,893 shares worth $12.7 million as of March 31. He joins his "tiger cubs" Chase Coleman and Steve Mandel as a shareholder.

While Robertson is enthusiastic about China's Amazon, he is not so bullish about Amazon (AMZN) - Get Report. In fact, his sentiment is quite the opposite.

For the second quarter in a row, Robertson's 13F revealed a sizable put option on Amazon. At the end of last year's fourth quarter, the stake was valued at $49.6 million. It has since increased to $86.9 million.

Tiger Global Goes Old School

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Chase Coleman's Tiger Global Management is known for its talent in picking technology stocks. Its venture capital arm has invested in big names like Survey Monkey, Quora and Credit Karma and bought pre-IPO shares of Alibaba (BABA) - Get Report long before the company's stock started to be traded on the New York Stock Exchange.

Tiger Global often goes for newer, more dynamic tech investments like Yodlee (YDLE) , TriNet Group (TNET) - Get Report and even Netflix (NFLX) - Get Report. But its latest public holdings disclosure revealed its stake in one of the oldest players in the game: IBM (IBM) - Get Report. The firm purchased 141,823 shares of IBM in the first quarter. Its stake, valued at $22.8 million as of March 31, has just a 0.25% allocation among its public equity holdings.

IBM hasn't been one of the best-performing stocks on Wall Street in recent quarters; billionaire investors, however, seem to think there is still something to it.

Warren Buffett has stuck by the stock quarter after quarter and at the start of 2015 raised his stakes yet again to 79.6 million shares. In March, he provided CNBC a simple explanation for his decision to stand by IBM: He likes it.

"It's kind of been doing exactly what I like ever since we started buying it," Buffett said. "People have this misconception that when we buy a stock we want it to go up. That's the last thing we want it to do."

Leon Cooperman is a fan, too, and picked up 333,067 IBM shares during the first quarter of 2015.

Dan Loeb and George Soros Bet Against Small Caps

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In August 2014, George Soros made headlines after disclosing a sizable put option in the SPDR S&P 500 ETF (SPY) - Get Report, which some took to be a defensive bet against the market. By the fourth quarter of last year, he had downsized his S&P put stake significantly, to $166.5 million. But in the first quarter of 2015, he ramped it up again to $1.1 billion.

And that's not the only major index he's betting against.

In their most recent 13F filings, both George Soros and Dan Loeb disclosed notable put options on the iShares Russell 2000 Index ETF (IWM) - Get Report. The ETF follows the Russell 2000, which tracks the small-cap segment of the U.S. equity universe.

As of March 31, Soros' put is valued at $177.2 million,  quite a bit less than his anti-S&P bet but still significant. Loeb's stake against the small-cap ETF is much larger, worth $497.5 million.

In his first-quarter letter to Third Point investors, Loeb said his firm remains "constructive" about the U.S. Apparently that doesn't apply to small-cap companies.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.