Warren Buffett's Successor, Greg Abel, Pared Down Bank of America, and Piled Into a Virtual Monopoly That's Now Berkshire's 3rd-Largest Holding

Berkshire Hathaway's portfolio has meaningfully changed since Warren Buffett retired as CEO on Dec. 31.

Abel continued an eight-quarter streak of paring down Berkshire's stake in Bank of America -- and profit-taking likely tells only part of the story.

Meanwhile, an artificial intelligence (AI) pioneer has quickly become Berkshire's third-largest holding.

Although earnings season is often the pinnacle of each quarter for investors, don't overlook the value of 13F-filing season . A 13F allows investors to track which stocks Wall Street's savviest money managers, including billionaire investors, have been buying and selling.

Arguably, no 13F release is more anticipated than that of Berkshire Hathaway (NYSE: BRKA) (NYSE: BRKB) . Following Warren Buffett's retirement as CEO on Dec. 31, Greg Abel has been responsible for Berkshire's $358 billion investment portfolio . Based on Berkshire's latest 13F, detailing second-quarter trading activity, Buffett's successor continued to pare down Bank of America (NYSE: BAC) and absolutely piled into virtual monopoly Alphabet (NASDAQ: GOOGL) (NASDAQ: GOOG) for a second consecutive quarter.

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Warren Buffett retired as Berkshire's CEO on Dec. 31. Image source: The Motley Fool.

Although Berkshire's new boss sent Constellation Brands to the chopping block and meaningfully cut his company's stakes in Kroger and Capital One Financial , it's the 30,230,000 shares of BofA that were sold in the second quarter that stand out.