BIRD STRIKE CAUSED UNUSUAL ACFT VIBRATIONS.

Narrative

WE WERE CLBING OUT OF EWR AT 250 KTS; TO 14000 FT; BECAUSE OF ATC ENRTE SPACING AND LCL WX DEVS DUE TO LCL TSTMS. WE WERE THEN CLRED TO ACCELERATE TO 310 KTS AND CLB TO FL190. A FLT ATTENDANT IN THE REAR AREA OF THE ACFT CALLED AND RPTED A VIBRATION WAS FELT IN THE REAR OF THE ACFT. I HAD THE FO GO BACK AND HE CONFIRMED THE UNUSUAL VIBRATION. I BEGAN TO FEEL IT ON THE FLOOR OF THE COCKPIT AND ALSO IN THE RUDDER PEDALS. I SLOWED BELOW 280 KTS AND THE VIBRATION QUIT. I ELECTED TO RETURN TO EWR AND ASKED FOR CLRNC BACK. THERE WERE NO ABNORMAL ENG INDICATIONS. THE AUM'S; FRONT AND REAR; WERE NORMAL. I MOVED ALL FLT CTLS MANUALLY (RUDDER; AILERONS; TRIM; SPOILERS AND FLAPS) AND FELT NOTHING UNUSUAL. AFTER EXTENDING SLATS AND SLOWING TO 210 KTS; THE VIBRATION RETURNED. WE COULD FEEL IT IN THE RUDDER PEDALS AND ALSO IN THE FLAP HANDLE AND CONSOLE NEXT TO THE FLAP HANDLE. IT REMAINED ABOUT THE SAME INTENSITY THROUGHOUT THE APCH AND LNDG. LNDG WAS BELOW MINIMUM LNDG WT AND NORMAL. WE TOLD CTR AND ALSO APCH CTL WE WERE NOT DECLARING AN EMER. I DID NOT SEE A REASON TO DO SO. AFTER THE VIBRATION CEASED WHEN SLOWING AND WE DID NOT HAVE 1 INDICATION OR ABNORMAL READING IN THE COCKPIT; TWR AT EWR TOLD US THE EMER EQUIP VEHICLES WOULD BE ALONG THE RWY FOR OUR LNDG. WE FELT VIBRATION INCREASE SIGNIFICANTLY AS WE TAXIED FROM THE RWY TO THE GATE AREA. THE L ENG SHUTDOWN WAS NORMAL; BUT WHEN WE SHUT DOWN THE R ENG; THERE WAS A MUCH HIGHER VIBRATION LEVEL (EVEN TO THE DEG OF A SHUDDER) AS IT WOUND DOWN. EWR STATION WAS CALLED AND NOTIFIED WELL IN ADVANCE OF OUR ARR BY RAMP RADIO AND A CHANGE OF DEST WAS SENT TO ACR BY ACARS. ZNY DID A FINE JOB HANDLING US. WE MADE A 180 DEG INTO THE EVENING WBOUND DEP TFC OUT OF NY AREA WITH A LINE OF TSTMS ALSO RESTRICTING THE ARR AND DEP PATHS. OUR 2 MAN COCKPIT WORKLOAD WAS AT ABOUT MAX WITH THE MANY HDG; SPD; AND ALT CHANGES. I HAD TO MAINTAIN COMS WITH OUR FLT ATTENDANTS; PA ANNOUNCEMENTS TO THE CABIN TO KEEP OUR PAX INFORMED AND COMPLY WITH ATC CLRNCS. ACR WAS NOTIFIED BY ACARS AND EWR STATION NOTIFIED BY RAMP RADIO. AFTER LNDG; INITIAL INSPECTION SHOWED A BIRD LODGED IN THE L MAIN GEAR AND POSSIBLE ENG COMPRESSOR BLADE DAMAGE. THIS HAD TO BE WRITTEN BEFORE I WAS ABLE TO OBTAIN FINAL DAMAGE RPT FROM MAINT. BIRD STRIKE WAS CAUSE.