As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BIRD STRIKE CAUSED ENG BLADE DAMAGE. AIR RETURN TO SGF.LOUD VIBRATION AFTER ROTATION ON TAKE OFF.CONTINUED TO FL280.DETERMINED WAS POSSIBLY THRUST RELATED IN AIR. EMERGENCY DECLARED. NO OVR WT LANDING. -C/A-PERFORMED BIRD STRIKE INSPECTION. REMOVED LEFT ENGINE BLADES 26 & 27 - S/N IHI4035K & IHI4014K - DUE TO BIRD STRIKE / INGESTION DAMAGE.