What was found
ORD FLT 711 EN-ROUTE ORD - PHX. AIRCRAFT WAS GROUNDED. ON TAKEOFF, JUST AFTER LIFTOFF, THE CREW HEARD A BANG, FOLLOWED BY A LOUD BUZZING VIBRATION. HIGHEST VIBRATION NOTED ON THE GAUGE WAS 6.2, #1 ENGINE. BURNED FUEL DOWN TO LAND BELOW MAX LANDING WEIGHT. THE FLIGHT DECLARED AN EMERGENCY AND RETURNED TO ORD WITHOUT FURTHER INCIDENT. FLIGHT LANDED AT 171,000, NO IN-FLIGHT SHUTDOWN. MAINTENANCE FOUND EVIDENCE OF A BIRD STRIKE IN THE #1 ENGINE. A BORESCOPE WAS PERFORMED AND A BIRDSTRIKE WAS CONFIRMED, ALONG WITH EXCESSIVE DAMAGE TO THE COMPRESSOR SECTIONS. REMOVED AND REPLACED #1 ENGINE PER JOB CARD 26L40071004 AND 26L00071015 LEAK CHECK OPS CHECK NORMAL.