Source: Steve Snodgrass via Flickr.

Every quarter, large money-managers have to disclose what they've bought and sold via "13F" filings. While Fools don't always follow what the big money does, we can often glean an idea or two by tracing their footsteps.

Kyle Bass, founder of Hayman Capital Management, is best known for shorting the subprime mortgage securities that nearly crippled the economy, effectively "calling" the economic recession and making a boatload of money at the same time. And while it doesn't have anything to do with real estate -- an area Bass clearly knows well -- Hayman Capital Management's largest stock holding since late 2013 has been General Motors Company (NYSE:GM)

This past quarter, Hayman Capital sold 1.5 million shares of General Motors. Let's dig into this move.

Buying and selling for several quarters 
Hayman Capital first opened a position in General Motors during the fourth quarter of 2013, and it added almost 2.5 million shares to that position in the first quarter of 2014. Here's a look at the price action of GM stock over the period since Hayman first opened a position:

GM data by YCharts. Arrows added by author.

The green arrows mark the low points in the quarters when Hayman bought, and the red arrow marks the high price in the quarter when Hayman sold. At best, Hayman would have made about a 10% return on the GM stake it sold.

A big fat caveat
Even after Hayman Capital sold 1.5 million shares, GM was still its largest stock holding at the end of the recorded period. The percentage of Hayman's portfolio invested in General Motors actually increased from 23% at the end of the first quarter, to nearly 28% at the end of the second quarter.

What does this tell us? Not much.

First, digging just a little deeper into Hayman's 13F filings shows us something important: The value of Hayman's stock portfolio declined a whopping 29% from one quarter to the next from $1.04 billion to $732 million. This is why basing your investments on the moves of large money-managers is rarely a good idea. The reality is that we have almost no idea why this happened.

Because we can see the changes in holdings at the fund, we do know that Bass sold off a lot of positions, including Kinder Morgan (NYSE:KMI)Vodafone Group Plc (NASDAQ:VOD), and Verizon Communications (NYSE:VZ), which collectively accounted for more than 27% of the hedge fund's stock position.

Comparing a hedge fund's holdings to our own can be like comparing apples and catfish.

But we don't know why Hayman Capital would have exited so many large positions and reduced its largest holding. Did a big investor cash out of the fund? Is Bass expecting a market correction? Has the fund invested in non-public securities that we don't see, given that 13Fs disclose stock holdings only? There could be any number of reasons, and hedge funds' motivations for buying and selling are often far different from those of the individual investor.

Picking good investments is hard enough without trying to read the minds of a hedge fund manager and his staff.

Focus on the business, not a total stranger's actions
Don't forget that Kyle Bass is managing Hayman Capital Management's portfolio and not yours. The objectives of the fund's investors may not be aligned with yours, so acting based on someone else's moves can lead to disaster. Further, 13F data is dated as soon as it's publicly available. It's mid-August, and we're talking about Hayman Capital's holdings at the end of the quarter ended June 30; we don't know how much the fund paid for its shares, how much it sold them for, or when the trades happened. 

Looking at what the big money does isn't a bad place to start, but it's not where your bucks should stop.