B757 CAPT REPORTS WINDSHEAR WARNING AT 700 FT AGL ON APPROACH. DURING RECOVERY CAPT NOTES LARGE AIRSPEED DISCREPANCY BETWEEN CAPT AND FO AIRSPEED INDICATORS.

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WE WERE LINED UP FOR A VISUAL APCH; FULLY CONFIGURED AND DSNDING OUT OF APPROX 700 RA WHEN WE RECEIVED AN AURAL 'WINDSHEAR!' AND THE WINDSHEAR ANNUNCIATOR ON THE PNF'S ADI. PNF CALLED OUT 'WINDSHEAR!' RECOVERY! (I DON'T KNOW WHY I ADDED 'RECOVERY' BUT I DID.) WITHIN A SPLIT SECOND; PF WAS EXECUTING THE WINDSHEAR RECOVERY MANEUVER. I SCANNED BACK AT MY (PNF) INSTS AND NOTICED MY AIRSPD INDICATOR ROLLING BACK PAST REF AND AS IT MOVED TO -10 REF; I COMMANDED 'PITCH! PITCH! PITCH!' (JUST TO EMPHASIZE TO THE PF THAT WE NEEDED TO GET OUT OF THIS WINDSHEAR.). SECONDS AFTER THE COMMAND; I SCANNED MY INSTS AND NOTICED MY AIRSPD INDICATOR WAS ABOUT 30 KTS SLOWER THAN MY STANDBY ASI AND MY FO'S ASI. WE WERE CLBING OUT OF ABOUT 1500 FT WHEN I ALERTED THE FO OF THE ASI DISCREPANCIES AND WE BOTH DECIDED THAT THE WINDSHEAR EVENT WAS A FALSE WARNING AND THUSLY TRANSITIONED TO A GAR. WE ADVISED ATC AND BEFORE RETURNING TO THE ARPT NEEDED TO TALK TO MAINT AND RUN SOME CHKLISTS. WE ADVISED MAINT WE HAD 2 EICAS MESSAGES: 'RUDDER RATIO' AND 'MACH TRIM FAIL;' AND 1 STATUS MESSAGE 'ELEVATOR ASYMMETRY.' MAINT TRIED TO TROUBLESHOOT AND HAD NO LUCK GETTING THE EICAS MESSAGES TO GO AWAY. WE NOTED THE 15 KT XWIND RESTR DUE TO THE RUDDER RATIO MESSAGE AND FO DISCUSSED THE POSSIBILITY OF ANOTHER WINDSHEAR WARNING AND STALL WARNING ON FINAL (WHICH WE DID NOT RECEIVE DURING THE PREVIOUS WINDSHEAR EVENT). WE ELECTED TO IGNORE THE WARNING IF OTHER INDICATIONS LOOKED NORMAL. WE LANDED WITHOUT INCIDENT AND I BRIEFED THE FLT ATTENDANTS AFTER THE FLT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: POST FLIGHT INSPECTION BY MAINTENANCE REVEALED THAT A BIRD STRIKE HAD OCCURRED ON THE LEFT SIDE OF THE RADOME; JAMMING BIRD DEBRIS INTO THE CAPT'S PITOT TUBE; RENDERING IT INOPERATIVE.