BOSTON ( TheStreet) -- The managers of Fidelity's biggest mutual funds have been cautious this year, judging from portfolio changes in the past few months. They mostly nibbled at stocks that the Boston-based fund firm already owns.Fidelity's fund managers are known for sharing their best investment ideas with one another so it's not unusual for new buys, or sells, to ripple through portfolios company-wide, which can affect the markets. But, this year, it looks like most of the big guys are standing pat. Fidelity manages 323 equity mutual funds with $635 billion in assets, making it one of the country's largest money managers. To get an idea of its girth and potential market impact, Fidelity is the biggest shareholder of iPhone and iPad maker Apple ( AAPL), with 49 million shares at the end of 2011, or 5.3% of Apple's outstanding shares. That's about 1 percentage point more than the stake of the next-largest shareholder, Vanguard Group. So a sampling of Fidelity's biggest funds' recent behavior can give a taste of what its market-moving funds are up to. In this exercise, I reviewed the top 100 stock holdings of five of the biggest, actively managed funds, four with quarterly changes through the end of February and the other, the Fidelity Low-Priced Stock Fund ( FLPSX), as of the end of January. The Fidelity fund managers' largest purchases were additions to existing positions in software and services giant Microsoft ( MSFT) (the company now owns just over 1% of its shares), wireless chipmaker Qualcomm ( QCOM) (it's the second-largest shareholder, with 3.8% of its shares), and cable-TV operator and entertainment conglomerate Comcast ( CMCSA) (1.6% of its shares). The $61 billion large-cap Fidelity Contrafund ( FCNTX ), up 14.4% this year, initiated two new positions: credit-card processor American Express ( AXP) and (new to this fund) Comcast, but those companies have been held by other funds within the Fidelity family off and on for some time. The biggest additions in the top 25 holdings of the 414-stock portfolio were of banker Wells Fargo ( WFC), at 3.5 million shares, which makes it the seventh-biggest holding at 2% of the portfolio, and Qualcomm, with a purchase of 1.8 million shares. Qualcomm is now its 15th-largest holding at just over 15 million shares.