As long as they are not salted and they are getting grit. Their system does not handle excess salt very well. I don't know that they will get many nutrients out of them, but it won't hurt them in any way that I am aware of.
When I throw the leftover seed out from feeding my caged birds, the chickens go crazy over the seeds. They eat everything, seed, shell, pellets, etc. and have not had any problems. I also feed them black oil sunflower seeds and they gobble them, seed and shell.