Definition
Accumulations of twigs, grass, feathers, or similar material built by birds inside engine cowlings, air intakes, exhaust outlets, pitot tubes, or other openings on a parked aircraft. Considered foreign material that must be located and removed during preflight inspection because it can block airflow, restrict cooling, obstruct instrument sensing, or cause a fire when the engine is started.
Plain English
Nests built by birds in or around the airplane while it sat on the ground. Even small ones are a real problem because they can block air, jam moving parts, or catch fire.
Context Anchor
Seen during the preflight inspection of the engine compartment, cowling, air inlets, and other openings where birds may have placed nesting material.
Why Pilots Care
Undetected bird nests can cause engine overheating, propeller damage, or in-flight power loss when material is ingested on startup or takeoff.
Intuition Check
Do not treat bird nests as just a cleanliness issue. Around an aircraft engine, nesting material is a safety hazard because it can burn, block airflow, or interfere with moving parts.
Example Sentence 1
During preflight, the pilot opened the oil access door and shone a flashlight around the cylinders to check for bird nests before the first flight of the day.
Example Sentence 2
A thorough engine compartment inspection is required after the aircraft has sat outside to ensure no bird nests remain in the air intake.