Every quarter, many money managers have to disclose what they've bought and sold, via "13F" filings. Their latest moves can shine a bright light on smart stock picks.

Today let's look at Robeco Investment Management, which is a U.S.-focused subsidiary of major Netherlands-based financial institution Rabobank and which has three primary divisions: Boston Partners (value equity), Sage Capital (multi-manager strategies), and Weiss, Peck, & Greer (fixed income, equity, and alternatives). It has been in the news a bit lately, with Rabobank trying to sell its investment management business and some suitors, such as Australia's Macquarie Group, not wanting all of the U.S.-based business.

Robeco Investment Management touts its flat management structure and focus on value equity investing. The company's reportable stock portfolio totaled $36.8 billion in value as of March 31.

Interesting developments
So what does Robeco's latest quarterly 13F filing tell us? Here are a few interesting details.

The biggest new holdings are Liberty Media and AbbVie. Other new holdings of interest include The Active Network (ACTV), which specializes in online registrations for endurance events such as marathons and triathlons. The company recently signed a three-year deal with Ironman, and its most recent quarterly earnings report featured revenue up 12% and shrinking losses. Some have questioned the company's solvency, while others like its valuation.

Among holdings in which Robeco Investment Management increased its stake were American Capital Agency (AGNC -1.23%) and RF Micro Devices (NASDAQ: RFMD). American Capital Agency is a mortgage REIT with a tantalizing dividend yield above 16%. The company's CEO is well respected, but some worry that mortgage REITs may lose a valuable tax advantage.

RF Micro Devices, specializing in high-performance radio-frequency technology, enjoyed an analyst upgrade in March, because of its successful diversification away from Nokia and its profitable growth in Samsung and Apple devices. Since then, the stock has hit a 52-week high, and some are hoping that it will do a lot of business in China. Its recently reported fourth quarter featured revenue up 49% over year-ago levels. Still, RF Micro Devices faces serious competition, such as from Qualcomm.

Robeco Investment Management reduced its stake in lots of companies, including Heckmann (NESC), which provides water-related services and chemicals for the growing (but controversial) fracking method of gas extraction. (It handles waste disposal, too, among other things.) Heckmann recently posted a disappointing earnings report, but management expects solid organic growth and sees pricing stabilizing.

Finally, Robeco's biggest closed positions included Starz and Sirius XM Radio (SIRI -3.01%). Sirius did post disappointing earnings recently, but revenue and earnings are still growing at a double-digit rate, so things aren't that dire. In fact, a strong report from Ford bodes well for the company, as its radios are embedded in many vehicles, and many are bullish about the company's new personalized radio service, MySXM. It's worth noting that while Robeco sold out of Sirius, it added shares of the company's majority stakeholder, Liberty Media.

We should never blindly copy any investor's moves, no matter how talented the investor. But it can be useful to keep an eye on what smart folks are doing, and 13F forms can be great places to find intriguing candidates for our portfolios.