A rebound in the US manufacturing sector last month failed to boost US stocks in early trade Monday after their record run at the end of last week.
But the takeovers of drug developer Covance and digital marketer Sapient showed there was still energy on New York trading floors.
An hour into trade, the Dow Jones Industrial Average stood at 17,357.96, down 32.56 points (0.19 percent).
The broad-based S&P 500 lost 1.37 (0.07 percent) to 2,016.68, while the tech-rich Nasdaq Composite added 12.49 (0.27 percent) at 4,643.23.
The ISM purchasing managers index for October recovered to 59.0, with companies saying activity is picking up more than expected going into the year-end holiday shopping season.
But the Commerce Department reported Monday that US construction spending fell a second straight month in September, for a 0.4 percent annual decline, surprising analysts who expected a pickup.
Covance shot up 25.3 percent on news that it will be acquired by Laboratory Corp. of America for $5.6 billion to create a giant in healthcare diagnostics. LabCorp fell 7.8 percent.
Sapient soared 42.1 percent on news it will be acquired by French public relations giant Publicis for $3.7 billion.
Bond prices were mixed. The yield on the 10-year US Treasury held steady at 2.34 percent, while the 30-year rose to 3.07 percent from 3.06 percent Friday. Bond prices and yields move inversely.