It's that time of the year again. It's 13F season, which means some of the largest money managers are detailing what their funds and companies were buying and selling in the fourth quarter of 2015 via the SEC-mandated 13F filing.

Berkshire Hathaway (BRK.A -0.35%) (BRK.B -0.28%) just filed its 13F. The filing reveals that Berkshire added to five companies it already owned, reduced the size of two positions, and completely sold out of another company. The table below summarizes the change in its portfolio during the fourth quarter of 2015.

Company

Change in Shares (Position Size)

Ownership of Company

Wells Fargo

+9,411,911 (+2%)

9.39%

Deere

+5,832,040 (+34%)

6.97%

AT&T

-12,743,618 (-21%)

0.76%

Axalta Coating Systems

+124,526 (N/A)

N/A

Liberty Global

+587,011 (+4%)

1.46%

Kinder Morgan

+26,533,525 (NEW!)

1.19%

WABCO Holdings

-227,974 (-6%)

5.8%

Chicago Bridge & Iron

-1,983,190 (-100%)

0%

Source: WhaleWisdom.com

Interestingly, only one of the positions changes this quarter appears to have been at Buffett's behest: the Wells Fargo stake that Berkshire Hathaway has owned for decades. Buffett apparently took advantage of a fourth-quarter decline in banking stocks to add to his Wells Fargo holdings.

Buffett has to be selective about when to add to the Wells Fargo stake. As a bank holding company, Berkshire cannot buy more than 10% of the firm. Once it reaches that limit, Berkshire's ownership of the bank can only grow by share count reductions at the San Francisco-based bank. (Berkshire's stake in American Express is similarly restricted, as the card company converted into a bank holding company during the financial crisis.)

The remaining position changes appear to be the work of Ted Weschler and Todd Combs, who each manage multi-billion dollar portfolios inside the Omaha-based conglomerate. 

A hidden addition
In recent weeks, Berkshire Hathaway has been a serial filer of SEC form 4 filings, which detail recent purchases of Phillips 66 (PSX -3.48%). As of the most recent form 4, Berkshire held about 75.55 million shares of the company, a substantial increase from the 61.49 million shares it reportedly owned at the end of December.

Many wondered if Berkshire's form 4 filings were indicative of the company's interest in the oil patch. Now that we know the company added Kinder Morgan into the portfolio in the fourth quarter, it appears that one of Berkshire's younger portfolio managers is capitalizing on depressed energy valuations by selectively adding them to his portfolio.

Besides that one addition, however, it was a relatively light quarter of trading for Berkshire, which prefers to buy and hold rather than actively trade in and out of its portfolio companies anyway.