On November 2, 1995, at 1828 eastern standard time, a Boeing 737-3B7, N373US, operated by USAir as flight 1669, struck a bird in the number 2 engine, during takeoff from the Portland International Jetport, Portland, Maine. The occupants were not injured, and the airplane received minor damage. Instrument meteorological conditions prevailed, and the scheduled, domestic, passenger/cargo flight was operated on an Instrument Flight Rules (IFR) flight plan under 14 CFR 121. The CAPTAIN'S REPORT OF NON-STANDARD OR IRREGULAR OPERATION stated: At takeoff rotation we experienced an apparent bird strike in the #2 engine followed by a loud bang & excessive engine vibration. #2 engine was shut down, an emergency was declared & emergency procedures were followed ending with an uneventful single engine landing. According to the Powerplant Group Chairman Report, conducted by a Safety Board Investigator from RE-40, Aviation Engineering Services: ...The fuselage adjacent to the No. 2 engine did not have any apparent damage from engine debris. An inspection of the entire airplane did not show any indications of other bird impacts or damage...There were no penetrations through any of the engine casings...Feathers and other organic debris identified to be bird remains were found in the fan, compressor, and combustor. There was no indication of any preexisting engine damage...Feather pieces...[were identified] as a female Common Eider (Somateria mollissima). The weight of the female Common Eider can range from 42 to 103 ounces (2.7 to 6.4 pound) with the average weight being 61 ounces (3.8 pounds)...The airworthiness certification requirements for bird ingestion into a turbine engine...states, in part that the engine must demonstrate that the ingestion of a 4- pound bird may not cause the engine to catch fire, burst or release hazardous fragments through the engine case, generate loads greater than the engine mount attachment ultimate load limits, or lose the capability of being shut down...the fractured fan blades, and the gearbox mount pad adapter were returned to the NTSB Materials laboratory to determine the mod of fracture. Examination showed all the fractures were due to overstress, with no evidence of progressive cracking...