An E190 experienced a damaging bird strike to the left engine shortly after takeoff and returned to the departure airport for maintenance.

Narrative

First Officer flying. Had just passed 1000 feet AGL; selected FLCH and 210 KTS; autopilot on and were accelerating through approximately 150 KIAS in a right turn to our assigned heading of 360 when we felt and heard an impact/bang sound. The aircraft abruptly decelerated and yawed left then began vibrating moderately. I was heads down at the time (monitoring the flap speeds) and checked the engine gauges. All were green except the vibration indicator on #1 engine (yellow). Additionally; #1 N1 was fluctuating. I told the First Officer that we had an engine problem; possibly a compressor stall on the #1 engine; to continue flying; that I was going to disconnect the autothrottle and retard the #1 thrust lever. First Officer acknowledged and stated that we might have taken a bird strike. (First Officer had seen a large object flash by the cockpit out of the corner of her eye). The vibration diminished as the thrust lever came back and; just aft of vertical; engine parameters stabilized in the green and the vibration ceased. I put the lever in the idle position for the duration of the flight. We elected to leave the flaps extended in case of debris damage and to facilitate our approach and landing; so we stayed in the 150-170 KIAS speed range and planned a VFR straight in. We declared an emergency and stated our intentions; then the First Officer flew and communicated with ATC while I accomplished the QRH Engine Abnormal Vibration checklist; informed the flight attendants and passengers that we had an engine problem; possibly a bird strike; and would be returning to the departure airport for a normal landing and taxi in. As I was preparing for the approach the Lead Flight Attendant called to tell us that a passenger could see bird strike damage to the #1 engine. The approach and landing were uneventful. After the initial inspection at the gate one of the mechanics asked us if we had hit a deer!