Billionaire investor George Soros's Soros Fund Management LLC reported sharply higher positions in Google Inc. (GOOG), Delta Air Lines Inc. (DAL) and Wells Fargo & Co. (WFC) in the fourth quarter, but no stake in e-commerce giant Amazon.com Inc. (AMZN).

The fund boosted its stake in Google by 258,774 shares to 259,900. The position is valued at $168 million and is now one of the largest in the portfolio.

The period marked a dramatic change for Soros, whose portfolio dropped to 145 holdings, down roughly two-thirds from the 473 positions held at the end of the third quarter. Overall, the value of Soros's holdings fell to $4.6 billion as of Dec. 31, down from $5.8 billion as of Sept. 30, according to a quarterly filing with the Securities and Exchange Commission.

Soros disclosed owning 1.8 million shares of Delta Air Lines, up from 28,200 the prior period. The position was valued at $14.3 million on Dec. 31. The Soros fund also reported its holding in Wells Fargo had risen tenfold to 1.2 million shares. It was worth $33 million.

Among new positions, Soros reported 210,300 shares of building-materials maker Owens Corning Inc. (OC), valued at roughly $6 million.

Soros didn't report a stake in Amazon, a company the fund had owned in the previous quarter.

Soros, who once dubbed gold "the ultimate asset bubble," again juggled his positions in the precious metal, raising his stake in the SPDR Gold Trust (GLD), a gold-backed exchanged-traded fund, to 85,450 shares, up from 48,350 shares in the period period. The position was worth $13 million.

Soros, who had disclosed call and put options on the gold fund in the prior period, reported no such investments in the fourth quarter.

In December, the Wall Street Journal reported that Soros's family fund purchased $2 billion of European bonds that were once owned by MF Global Holdings Ltd., the same debt that helped force the securities firm into bankruptcy protection.

Last July, Soros said he would turn his hedge-fund firm into a "family office," a move that allows it to avoid a new level of regulatory oversight facing many hedge funds.

Many investors that manage more than $100 million are required to file with the SEC Form 13-Fs disclosing their stock holdings within 45 days of the end of a given quarter, giving the public its freshest possible glimpse into the portfolios of well-known money managers. The fourth-quarter deadline was Tuesday.

-By Brett Philbin, Dow Jones Newswires; 212-416-2173; brett.philbin@dowjones.com