I've also seen reports in the news where Australia needs more seasonal agricultural workers, as Australians don't necessarily want to do the work. Most recently there's been a trial program to get pacific islanders in on temporary visas to work these farms. And traditionally it's been backpackers that have worked these fruit-picking and misc jobs.
So it seems to me that a lot of the population of the "developed" world, especially the native people, don't want to be doing those menial, labour intensive, and repetative jobs themselves. Also I don't believe that the immigrants that do these jobs now want their kids to be doing them. Therefore I would say that we should work harder to try and automate these kinds of menial mind-numbing jobs as best as we can.
Sitting on your behind is easier, regardless of pay.
Sources: BLS http://www.bls.gov/oes/current/oes_nat.htm#45-0000 http://146.142.4.24/cgi-bin/cpicalc.pl?cost1=12.00&year1...
The Pew Hispanic Center estimates that in the 1980s the net advance of the undocumented population was at the 130,000 per year, increasing to 450,000 per year from 1990–1994, and further increasing to 750,000 per year from 1995–1999, and staying at 700,000–850,000+ per year since about 2000
(see http://en.wikipedia.org/wiki/Illegal_immigrant_population_of... )
Why?
"Free trade" destroyed many US factory jobs, but it vaporized Mexican agriculture. Small proprietor farms were out of business overnight by the flood of cheap US corn.
The human element in illegal immigration is usually completely ignored. People don't pull up stakes and walk across a desert because they think that working in a poultry slaughterhouse is a great life. They do so because it is a better life than complete destitution that they face at home.
Either way, i think we're well served by including some specific claims (and that's why i cited the wikipedia page)
If you look at states like Georgia (and i've seen similar articles about parts of the UK), there's a massive shortage of farm workers, and regardless of what the supply of illegal migrant workers is. Even after Georgia began holding farmers directly liable for employing illegal immigrants, local workers have not stepped up to fill the gap.
Besides, American immigration policy, rightly, allows white collar workers from other nations, especially Canada and Mexico into the country via NAFTA. That is, frankly, a good thing. All we're doing is keeping out a labor supply that is currently needed.
If you want to level the playing field for native low skill workers, require farmers and the like to pay all the taxes and health benefits for all their workers, illegal or not.