Date: 202012
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Climb
Aircraft component: Engine
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Departure Airport; General Maintenance Action
Contributing factors: Human Factors; Aircraft
Primary problem: Human Factors

Narrative: We took the aircraft that was returned to service after a large bird was ingested into the #1 engine on the previous flight. The #1 engine was started first prior to taxi out to ensure no issues with the engine. All engine indications after start were normal. The takeoff was normal with no abnormal engine indications. On departure just after retracting the landing gear; a strong smell from the previously ingested bird permeated throughout the aircraft. Shortly after; the forward lav smoke detector sounded. The aircraft was leveled off; and then we began to execute the Smoke; Fire or Fumes Checklist. Once stabilized on a left downwind with Departure Control notified; First Officer (FO) now flying; I contacted the Flight Attendants to confirm the status of the forward lav. They indicated that there was NO fire; just a very strong and pungent smell throughout the entire cabin. Fully aware that the cause of the alarm was the heavy fumes from the bird; we continued with the checklist and decided to discontinue the flight and return to the airport. We removed our masks; coordinated with Dispatch; and continued on downwind to set up for a visual approach and landing. Engine indications were normal the entire flight and the smell slowly dissipated. The forward lav alarm continued to sound; no fire though. No priority handling was requested. We landed uneventfully and taxied to the gate.The aircraft was returned to service after a bird was ingested on the previous flight. The engine contained a large amount of bird parts around the fan blades and some appeared to be ingested into the compressor section. Contract Maintenance cleaned and inspected the engine in coordination with Maintenance Control and signed off on the logbook. I did inquire of Maintenance about an engine run. They indicated it was not needed. I should have pushed them on it; as we were concerned about the large amount of bird guts all around the fan section. I did not inspect the engine after Maintenance completed their work and felt confident it was accomplished correctly; my mistake; should have crosschecked. The FO did a walkaround prior to departure and noted some bird parts still remaining. A borescope was not accomplished as Maintenance Control indicated it could be done within a couple of flight hours; most likely after the next flight since we were heading to a Maintenance base. Not sure Maintenance Control realized the significant amount of bird ingested into the engine. Could have communicated better with them.




Synopsis: B737-700 Captain reported taking an aircraft that had just been returned to service after a bird strike on the last flight.  The Captain stated a strong smell of bird permeated the entire aircraft during takeoff resulting in a return to the departure airport.