A B757 CREW; DEPARTING LIMA (SPIM); INGESTED A BIRD(S) INTO THE R ENG ON TKOF; REQUIRING A RETURN TO DEP ARPT WITH AN OVERWT LNDG BEING MADE.

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ON DEP FROM RWY 33 AT LIMA USING MAX PWR DUE TO ACCEPTABLE TAILWIND WE BEGAN OUR TKOF ROLL. PRIOR TO ROTATION I NOTICED WHAT LOOKED LIKE A BIRD RUNNING ACROSS THE RWY IN FRONT OF THE ACFT. SEEING NORMAL ENG INDICATIONS WE CONTINUED THE TKOF. ONCE IN THE AIR; I NOTICED A LOW PITCHED RUMBLING SOUND FOLLOWED BY THE R ENG VIBRATIONS INDICATOR TURNING AMBER AND DISPLAYING THE NUMBER 5. WE NOTIFIED ATC THAT WE HAD A PROB AND WANTED TO RETURN TO THE FIELD. THE FLT ATTENDANTS THEN CALLED TO TELL US THEY HEARD A LOUD RUMBLING AND THAT THEY SAW SPARKS COMING FROM THE COWL AREA OF THE R ENG. I THEN DECLARED AN EMER AND WE RECEIVED VECTORS BACK FOR AN APCH TO RWY 15. I NOTIFIED THE FLT ATTENDANTS THAT WE DID NOT ANTICIPATE AN EVAC AND THAT THEY SHOULD NOT BEGIN ONE WITHOUT HEARING FROM ME. WHEN THE THROTTLE OF THE R ENG WAS RETARDED; THE VIBRATION INDICATOR RETURNED TO NORMAL SO THE ENG WAS NOT SHUT DOWN. LNDG WAS MADE OVERWT; AT 238000 LBS AND TOUCHDOWN WAS SMOOTH. UPON RETURNING TO THE GATE AND SHUTTING DOWN; WE OBSERVED THAT 2 ENG FAN BLADES WERE BENT; APPARENTLY FROM THE IMPACT WITH WHATEVER WE HIT; BELIEVED TO BE A BIRD.