B737-700
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Commercial
Flight Crew Last 90 Days 187
Troubleshooting
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Bird / Animal
Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport
Aircraft; Environment - Non Weather Related
On Takeoff roll just after V1; I (Pilot Flying) noticed a flock of geese hanging out on the final 1/3 of Runway XX. As I rotated; they took off but stayed low. We informed Tower of the birds while entering initial climb. As we went to clean up the flaps; I noticed the engine telemetry boxes flashing white and the left (Number 1) engine indicated a low oil quantity. At this point; I indicated to the Captain (Pilot Monitoring) that the indication was abnormal and we thought it MIGHT be related to the birds on the runway. The Captain took controls and we leveled at 3;000 feet as per the clearance. We indicated to ATC that we might have a problem and that possibly the birds had something to do with it.While level; we assessed the condition of the engines and initially found the oil quantity to be decreasing in Number 1 as we added thrust. Then; the quantity levels stabilized. We initiated a climb with ATC to test the thrust/oil quantity/engine performance and found the Number 1 engine to be acting normally; but with a lower quantity than on the Number 2 and less than what we started the leg with. At this point; we determined that we needed to come back around for a landing and inspection in case there was bird ingestion or an engine oil problem (in an abundance of caution). We ran the QRH for engine shutdown just in case we actually lost the engine. We opted to perform a flaps 40 landing as we were overweight and had a 'normal' performing engine. We asked for an approach to Runway XX and had the trucks rolling so as to ascertain the physical condition of the aircraft before returning to the gate in ZZZ. The approach; landing; rollout; and taxi in were all uneventful. ARFF [Aircraft Rescue and Firefighting] found no damage to the aircraft (and no bird carcasses were found on the runway). Contract Maintenance performed the engine inspection as well as the overweight landing inspection; finding no damage. The result was a deferred Number 1 oil quantity indicator and oil service for both engines.
B737-700 First Officer reported possibly striking birds after takeoff.