Philadelphia Vireos were known in the Commonwealth as rare spring and uncommon fall migrants (Veit & Petersen 1993), with no previous records of breeding attempts in the records. They do breed in northern New York (McGowan & Corwin 2008), although that population is somewhat isolated from the rest of the North American breeders. There were no breeding records for Philadelphia Vireo during Atlas 1, but on June 12, 2011, several Atlas 2 volunteers were surprised to hear singing Philadelphia Vireos in a Stephentown block in Berkshire County, close to the border with New York. Upon closer inspection they surmised that they were observing a pair. They watched the birds, expecting they might reveal further evidence of Confirmed breeding, but the pair did not. Follow-up observations did not yield fruit. The species remains without a Confirmed breeding record in the state.