Date: 201711
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Light: Night
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb; Initial Climb
Airspace: Class C ZZZ
ATC / advisory: Tower ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Bird / Animal
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Aircraft Aircraft Damaged; Flight Crew Returned To Departure Airport; Flight Crew Landed in Emergency Condition; Flight Crew Landed As Precaution; Flight Crew Diverted
Contributing factors: Environment - Non Weather Related
Primary problem: Environment - Non Weather Related

Narrative: On initial climbout; we encountered an enormous flock of very large birds. At least one bird was engulfed in the number 2 engine and another struck the left retractable Landing light. We heard loud impacts of birds on both sides of the aircraft and noticed an immediate airframe vibration noise coming from the right side (number 2 engine). The number 1 engine seemed to not suffer damage and appeared to be operating normally. I was the Pilot Flying (PF); and lowered the nose to continue a shallow climb. This allowed me to reduce the thrust on the number 2 engine to reduce the vibration. At this reduced thrust setting; Vibration on the engine instruments indicated 2.4 on the number 2; and 0.7 on the number 1 engine (which was running at a much higher thrust setting). We didn't have much excess airspeed as we were very light out; but we continued a shallow climb allowing the aircraft to slowly accelerate as well. We notified Tower that we were returning to the field. I called the Flight Attendants and told them we were returning to [departure airport]. I didn't have time to notify the Passengers as we were quite busy. We were given a left turn to a heading of 010 and an altitude of 2000'. At that point we were climbing through 2300' so I descended back down to 2000'. Because of our close proximity to [the parallel runway] (the closer runway along our northern downwind track); we initially requested [a different runway] (for a more normal turn radius). However; there was Company traffic on a 10 mile final; so I requested [the parallel runway] and we widened our downwind leg some (to afford a normal turn to the closer [the parallel runway]). I operated the number 2 engine close to flight idle to reduce the airframe vibration. We utilized the FMC computed landing speeds; with Flap 30 and auto brakes 2. Our weight at this time was 111;000 pounds. Aside from the vibration coming from the number 2 engine; and the smell of cooked bird; we had no other abnormal indications. We configured the aircraft for landing; completed the Before Landing Checklist and made an uneventful landing. After we turned off the runway; I shut number 2; we started the APU; and taxied back to the gate we just departed.


Second narrative: Emergency vehicles and Personnel followed and met aircraft at gate along with Maintenance. We advised Passengers after returning to the gate on the ground.


Synopsis: B737 flight crew reported hitting a flock of birds shortly after takeoff. Immediatly after contact they experienced some abnormal engine indications; so they decided to return to the departure airport.