RETURN LAND MANDATED WHEN B737-800 FLT CREW; AFTER NOTING FUMES IN COCKPIT AND CABIN; SUSPECTS ENG DAMAGE DUE TO A BIRD STRIKE ON TKOF FROM MMCZ; FO.

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AFTER TKOF AROUND 800 FT AGL; A POP/BANG WAS HEARD. THE ACFT STARTED TO SHAKE AND VIBRATE AND THE CABIN AND COCKPIT WAS GETTING A STRONG BURNING ODOR. WE DID NOT KNOW IF A TIRE HAD BLOWN OR IF A BIRD STRIKE HAD HAPPENED. I DID SEE A FLOCK OF LARGE GULL TYPE BIRDS NEAR THE PLANE AS WE CLBED. IT WAS DIFFICULT TO KNOW EXACTLY WHAT WAS CAUSING THE VIBRATION AS ENG INDICATIONS WERE NORMAL AS WAS THE PERFORMANCE (THRUST). GIVEN THE UNCERTAINTY OF THE PROB; WE DECLARED AN EMER AND LANDED BACK AT CZM. THE LNDG WAS OVERWT BUT WAS SMOOTH AND UNEVENTFUL. NO EVAC WAS CALLED FOR. MECHS FOUND THE REMAINS OF A LARGE BIRD THAT WAS INGESTED INTO THE R ENG; THE INSPECTION FOUND SIGNIFICANT DAMAGE TO THE FRONT FAN BLADES. WE THINK THE INITIAL 'BANG' WAS A MOMENTARY COMPRESSOR STALL AND THE VIBRATION WAS FROM THE FAN BLADES 'CHEWING' THE BIRD UP UPON IMPACT. A BOX PATTERN WAS FLOWN IN VFR CONDITIONS BACK TO CZM. ALL APPLICABLE CHKLISTS WERE ACCOMPLISHED PRIOR TO AND AFTER LNDG. PAX DEPLANED AT THE STATION WITHOUT INCIDENT. THE CAPT AND I WAITED FOR ALL INSPECTIONS TO BE COMPLETED AND THEN DID A TEST RUN-UP ON THE ENGS. THE DAMAGED ENG HAD MUCH HIGHER VIBRATION READINGS THAN THE GOOD ENG AND WAS NOTED BY THE MECH IN THE COCKPIT WITH US. MAINT CTR SAID IT WAS CLOSE TO THE TOLERANCES. THE CAPT AND I ELECTED NOT TO FLY THE AIRPLANE AS A PORTION OF THE RTE WAS OVERWATER AT NIGHT. WE FELT THE DAMAGE WAS SIGNIFICANT FROM A PLT PERSPECTIVE AND THE SAFEST ACTION WAS NOT TO FLY IT. SUPPLEMENTAL INFO FROM ACN 617968: L LNDG GEAR AND FLAPS EXTENDED SUSPECTING TIRE FAILURE OR BIRD STRIKE. CLBED TO 2000 FT WHEREUPON VIBRATION SUBSIDED. LNDG OVERWT AT 147000 LBS.