Sure. Here are just a few of the ones I found back when I did the research. There are NUMEROUS sites out there that express the dangers of housing your rodents on pine and cedar. My favorite line out of all of these sites is this one:
"Several people have claimed that their pet rodents have always been kept on pine or cedar with no adverse effects. However, animals with elevated liver enzymes do not show any symptoms, and unless these animals received full autopsies at death with no sign of enlarged livers or liver disfunction, respiratory infection, or altered immune system, how can they claim that the pine or cedar did not affect them? " Source
I have been just as guilty of housing my rodents on pine as the next guy or gal, but through research, I found that what I was doing, might actually be HARMING my rodents. Feeders or not, pets or not.....they have a right to live the best life they can while they do.
The Rat Fan Club
AFRMA
About.com
Ratsrule.com <---has more links.
Maybe there isn't "scientific" evidence to back up the dangers of pine, but with all of the testing that has been done and whatnot....are you willing to take a chance that it's not? I know one thing....I certainly wouldn't want to be one of your rats.