2006 Ford Taurus Squeak and clicks loud at startup

i get a high pitch squeaking sound around the rear portion of the cylinders [opposite the belt]. the sound is more pronounced when the engine is cold and dwindles down to a rythmic 'bird squeak' once the car is warmed up. I do not feel the car run any more rough since sqeaking started. The squeak is quite loud in some instances of cold [morning] starts and is less so when the car is re-started throughout the day. Along with the sqeak, I can detect a less prominent, metallic clicking. The clicking/squealing frequency changes in concert with the engine rpm and does seem to quiet down a bit a higher rpms.