* Facebook shares pare losses, Qualcomm up
* S&P on track to close best month since Oct 2011
* Constellation brands shares tumble on DOJ action
* Indexes: Dow off 0.1 pct; S&P flat; Nasdaq up 0.2 pct
By Angela Moon
NEW YORK, Jan 31 (Reuters) - U.S. stocks were little changed on Thursday as investors were cautious after a mixed bag of economic data, while stellar earnings from chipmaker Qualcomm helped the Nasdaq index to edge higher.
The S&P 500 is on track to post its best month since October 2011 and its best January since 1997.
Investors expect a pullback in equities after the recent gains, though they have bought on dips over the past four weeks. The largest daily decline on the S&P 500 so far in 2013 was Wednesday's 0.39 percent drop after data showed the economy contracted in the fourth quarter of 2012.
On Friday, the government is due to release figures on January's non-farm payrolls, which are expected to show employers added 160,000 jobs in January after a rise of 155,000 in December.
"It's the calm before the potential storm. The uncertainty about tomorrow's numbers comes from that fact that we had a decent ADP report but the weekly claims were not so great," said Randy Frederick, managing director of active trading and derivatives for Charles Schwab in Austin, Texas.
"We could see an overly sensitive market to a bad number tomorrow, given that we've been up without a major correction, and that makes the market sensitive to the downside."
Data on Thursday showed a slight rise in weekly jobless claims and incomes growing at the best pace since 2004, underscoring how fragile the economic recovery still was.
Friday will also bring reports on consumer confidence, U.S. manufacturing, construction spending and car sales.
Qualcomm gained 4.4 percent to $66.32 as the top boost to the Nasdaq Composite after the world's leading supplier of chips for cellphones beat analysts' expectations for quarterly profit and revenue and raised its targets for the year.
Facebook shares fell 0.8 percent to $31.01 after falling as low as $28.74 a day after the social network company said it doubled its mobile advertising revenue in the fourth quarter. However, growth trailed some of Wall Street's most aggressive estimates.
The Dow Jones industrial average was down 7.50 points, or 0.05 percent, at 13,902.92. The Standard & Poor's 500 Index was up 0.36 points, or 0.02 percent, at 1,502.32. The Nasdaq Composite Index was up 6.99 points, or 0.22 percent, at 3,149.29.
The S&P 500 has advanced more than 5 percent in January after legislators in Washington temporarily sidestepped a "fiscal cliff" of automatic tax increases and spending cuts that could have derailed the recovery. Better-than-expected corporate earnings have added to the gains.
It would be the benchmark's largest monthly advance since a more than 6 percent gain in October 2011 and the best January advance since a 6.1 percent jump in 1997.
UPS shares lost 2.1 percent to $79.50 after reporting fourth-quarter earnings that were below analysts' estimates on Thursday and forecasting weaker-than-expected profit for 2013.
Constellation Brands shares tumbled 16.4 percent to $32.72 after the U.S. Justice Department moved to stop Anheuser-Busch InBev from buying the half of Mexican brewer Grupo Modelo that it does not already own. Constellation would have distributed Corona beer in the United States if the transaction had been approved.
Tank barge operator Kirby Corp added 6.3 percent to $70.67 and transportation company Ryder Systems climbed 4.8 percent to $56.84 after posting quarterly results.
Thomson Reuters data through Thursday morning shows that of the 231 companies in the S&P 500 that have reported earnings this season, 69.3 percent have exceeded expectations, a higher proportion than over the past four quarters and above the average since 1994.
Overall, S&P 500 fourth-quarter earnings are forecast to have risen 3.7 percent. That's above a 1.9 percent forecast at the start of the earnings season but well below a 9.9 percent profit growth forecast on Oct. 1, the data showed.
Slot machine maker WMS Industries surged 51.7 percent to $24.84 after the company agreed to be acquired by Scientific Games for $26 per share in cash. Scientific Games jumped 5 percent to $9.38.