What was found
EICAS MSG, ATL DISAGREE AT FL 300, CAPTAINS 30000 & FIRST OFFICERS 30260, DESCENDED TO FL 280. FOUND THE FIRST OFFICERS PITOT STATIC PROBE, RT SIDE STATIC PORT PLUGGED WITH BIRD WASTE. R & R PITOT STATIC PROBE IAW AMM 34-11-01. FLUSHED SYS AS NECESSARY IAW AMM 34-11-00. R & R RT CADC IAW AMM0 34-12-01, CHECKED NORMAL. PERFORMED FULL RANGE LEAK CHECK IAW AMM 34-11-00, CHECKED NORMAL, CAPTAINS, FIRST OFFICERS & STBY ALT.