Bill Ackman's Pershing Square Capital Management kept things relatively quiet in the third quarter, making only minor portfolio tweaks rather than any dramatic moves. The biggest change? A modest trim of his Alphabet position, which gets more interesting when you consider Warren Buffett was moving in the opposite direction.

A Tale of Two Billionaire Investors

According to 13F filings disclosed Friday, Pershing Square cut its stake in Alphabet Class A (GOOGL) by 10%, bringing the position down to 4,843,973 shares. This comes after Ackman actually increased his Class A holdings in the second quarter, making the reversal somewhat notable.

The plot thickens when you consider that Buffett's Berkshire Hathaway (BRK.A) disclosed a fresh position in Alphabet Class A shares in the same quarter. It's the kind of passing-in-the-night moment that makes you wonder what each legendary investor sees that the other doesn't.

Minimal Portfolio Shuffling

Beyond the Alphabet adjustment, Pershing Square made only tiny trims to a handful of other positions. Each of these sales represented less than 1% of the fund's stake in the respective companies:

• Restaurant Brands International (QSR)
• Brookfield (BN)
• Uber Technologies (UBER)

Pershing Square didn't open any new positions during the quarter, nor did it increase its stake in any existing holdings. It was essentially a quarter of standing pat, with just a bit of portfolio housekeeping.

Where Ackman's Chips Are Stacked

Looking at the overall portfolio composition as of September 30, Uber (UBER) leads the pack at 20% of the fund, followed closely by Brookfield (BN) at 19%. These two positions represent nearly 40% of Pershing Square's disclosed equity holdings.

The complete top holdings breakdown looks like this:

• Uber Technologies: 20%
• Brookfield: 19%
• Howard Hughes Holdings (HHH): 11%
• Alphabet Class C (GOOG): 11%
• Restaurant Brands International: 10%
• Amazon.com Inc (AMZN): 8.7%
• Alphabet Class A: 8.0%
• Chipotle Mexican Grill (CMG): 5.8%
• Hilton Worldwide Holdings (HLT): 5.4%
• Seaport Entertainment Group (SEG): 0.8%

Together, Alphabet's Class A and Class C shares still represent about 19% of the fund's holdings, making Google's parent company a significant bet even after the recent trim. The portfolio remains highly concentrated, with the top three positions accounting for half of the fund's disclosed equity investments.

The relatively quiet quarter suggests Ackman remains confident in his existing positions and isn't seeing compelling opportunities that warrant major new bets or significant reallocations. For an activist investor known for making bold, concentrated wagers, sometimes the most interesting move is not making one at all.