For Bill Ackman, the billionaire head of Pershing Square Capital Management, the first few months of the new year brought about a significant decrease in overall portfolio value. According to Seeking Alpha, Pershing Square saw its value decline from $5.87 billion to $4.83 billion in the first quarter of the year; this constitutes a decline of about 18%. Ackman's portfolio remained highly concentrated, focusing on just seven positions. Below, we'll explore how those positions changed over the course of the first three months of 2018, according to information available via the fund's 13F filing.

Pershing Exits Nike, Buys United Technologies

Two major changes to the Pershing Square portfolio this quarter included one liquidation and one new position entered. Ackman sold off Nike Inc. (NKE), exiting the position that formerly occupied about 6.22% of the portfolio. It was sold last quarter at prices ranging from $62.50 to $70, depending upon when in the three-month period Pershing Square sold the shares. Ackman had initially entered the position in the previous quarter, buying the stock at a price somewhere between $51 and $65 per share.

The only new stake that Pershing Square took on in Q1 of 2018 was in United Technologies Corp. (UTX). United occupies about 5% of the portfolio, according to the 13F, and Ackman bought shares for somewhere between $122 and $138 per share.

Ackman Holds Onto Restaurant Brands, Chipotle and ADP

Ackman is known for maintaining a condensed and highly concentrated portfolio. As such, his top three holdings account for about two-thirds of his entire 13F portfolio. These three names did not change from the previous quarter, and they include Restaurant Brands International Inc. (QSR), Chipotle Mexican Grill Inc. (CMG) and Automatic Data Processing Inc. (ADP). QSR occupies about 29% of the portfolio and is the single largest position in the 13F filing. Ackman trimmed his holdings by about 8% over the past quarter. ADP, on the other hand, represents about 19% of the fund's holdings, and Pershing Square sold off about 10% of its position in this stock during Q1.

Ackman also sold off portions of his other existing stakes, including Mondelez International Inc. (MDLZ), a position accounting for about 14% of the fund's portfolio. Pershing Square trimmed its holdings of MDLZ by about 30%. CMG has long been one of the most controversial holdings in Ackman's portfolio. This past quarter, he began and ended the period with the exact same number of shares of this stock; the fund held about 2.8 million as of the end of Q1. Ackman did not increase his positions in any existing names during the first quarter; his only purchase overall was in UTX during this time period.