RS: I don't think there is a problem with bird feeders as long as they are cleaned and sanitized weekly to prevent the spread of diseases, which I never seemed to get around to when we have used them in the past.
Supposedly song bird populations are declining mostly due to quality habitat losses. Probably 50% of TBN members are folks who have sprawled into the countryside and contribute to habitat losses and fragmentation, just as I have. Add to that the millions of CRP acres that have been pulled out of the program recently as grain prices rose. Feeding and/or making suitable habitat with natural food sources are ways to compensate for that I hope.
For example:
Pheasants Forever Press Release
"Pheasants Forever says the more troubling statistic is the 25 percent loss in Conservation Reserve Program (CRP) acreage in the state [S. Dakota] since 2007, a loss that finally appears to be catching up to the state’s overall pheasant population."