http://usatoday30.usatoday.com/money/workplace/2009-09-13-plants_N.htm
Immigration raids yield jobs for legal workers 

'When federal agents descended on six meatpacking plants owned by Swift & Co. in December 2006, they rounded up nearly 1,300 suspected illegal immigrants that made up about 10% of the labor force at the plants.

But the raids by Immigration and Customs Enforcement (ICE) agents did not cripple the company or the plants. In fact, they were back up and running at full staff within months by replacing those removed with a significant number of native-born Americans, according to a report by the Center for Immigration Studies (CIS).

"Whenever there's an immigration raid, you find white, black and legal immigrant labor lining up to do those jobs that Americans will supposedly not do," said Swain, who teaches law and political science."