* Homebuilders rally after existing home sales data
* Wisconsin Energy to buy Integrys for $9.1 bln
* ParkerVision plummets on its heaviest-ever volume
* Indexes down: Dow 0.2 pct, S&P 0.1 pct, Nasdaq flat (Updates to midday trading)
By Ryan Vlastelica
NEW YORK, June 23 (Reuters) - U.S. stocks fell slightly on Monday as investors found few reasons to keep buying following a six-day rally in the S&P 500, though homebuilders rallied on strong sales data.
The S&P is coming off its longest streak of advances since mid-April, and both it and the Dow closed at records on Friday. While Wall Street's uptrend is still viewed as intact, signs of mixed global economic growth could constrain further gains.
Financial data firm Markit's Composite Purchasing Managers' Index for the euro zone fell more than expected, though the HSBC/Markit Flash China Manufacturing Purchasing Managers' Index rose into expansion territory for the first time in six months.
U.S. data was positive, with May existing home sales rising 4.9 percent, more than twice the rate of growth that had been expected, while a preliminary read on June manufacturing rose more than expected to its highest since May 2010, according to financial data firm Markit.
"Right now we're digesting last week's gains and keeping an eye on all the economic data that's coming out this week," said Leo Grohowski, who oversees more than $184 billion in client assets as chief investment officer at BNY Mellon Wealth Management in New York.
"We're not likely to see a major pullback given healthy activity like buybacks and mergers, but today is a day of quiet consolidation."
The PHLX housing sector index gained 0.5 percent as one of the strongest sectors of the day. KB Home rose 1.5 percent at $17.50 while PulteGroup Inc added 1.4 percent at $19.93 and Toll Brothers rose 0.8 percent to $36.40.
The Dow Jones industrial average fell 28.74 points or 0.17 percent, to 16,918.34, the S&P 500 lost 1.44 points or 0.07 percent, to 1,961.43 and the Nasdaq Composite dropped 0.38 points or 0.01 percent, to 4,367.66.
Wisconsin Energy said it would buy Integrys Energy Group Inc in a deal valued at $9.1 billion while Oracle Corp agreed to buy Micros Systems in a $5.3 billion deal.
Shares of Integrys rose 12.3 percent to $68.40 as the S&P's biggest percentage gainer while Micros rose 3.3 percent. Wisconsin fell 3.1 percent to $45.45 while Oracle rose 0.7 percent to $41.08.
ParkerVision Inc plummeted 56 percent to $2.16 after a federal judge overturned a jury verdict that ordered Qualcomm Inc to pay ParkerVision $173 million for infringing patents. About 27 million Parker shares traded hands, its heaviest day of trading ever. (Editing by Nick Zieminski)