The "Eastern" Painted Buntings ARE decreasing in numbers and no one knows absolutely sure as to why. Possibly habitat loss, birds captured and sold/kept as pet birds, some other unknown cause, or a combination of many things .....
The PBOT research has pretty much run out of money even though the research is still operating on a shoe-string. It has only been the last 2 1/2 years that a bander in Florida has been capturing and banding them to aid in this research. Before that, there were mainly banders in NC and SC involved in this research project.
More information about the research can be found on the website:
http://paintedbuntings.org/
I have read that the "Western" Painted Bunting population is not at risk, only the Eastern birds.