AIM Text
- Bird strike risk increases because of bird migration during the months of March through April, and August through November.
- The altitudes of migrating birds vary with winds aloft, weather fronts, terrain elevations, cloud conditions, and other environmental variables. While over 90 percent of the reported bird strikes occur at or below 3,000 feet AGL, strikes at higher altitudes are common during migration. Ducks and geese are frequently observed up to 7,000 feet AGL and pilots are cautioned to minimize en route flying at lower altitudes during migration.
- Considered the greatest potential hazard to aircraft because of their size, abundance, or habit of flying in dense flocks are gulls, waterfowl, vultures, hawks, owls, egrets, blackbirds, and starlings. Four major migratory flyways exist in the U.S. The Atlantic flyway parallels the Atlantic Coast. The Mississippi Flyway stretches from Canada through the Great Lakes and follows the Mississippi River. The Central Flyway represents a broad area east of the Rockies, stretching from Canada through Central America. The Pacific Flyway follows the west coast and overflies major parts of Washington, Oregon, and California. There are also numerous smaller flyways which cross these major north‐south migratory routes.
Source: FAA Aeronautical Information Manual · current edition · paragraph 7-5-1.
Research Notes
AIM 7-5-1 covers Potential Flight Hazards — the broader category of in-flight risks that pilots must be aware of.
Categories of flight hazards:
- Weather (covered in AIM 7-1, 7-4)
- Wake turbulence (AIM 7-3)
- Bird strikes (AIM 7-4)
- Mid-air collision (avoidance via see-and-avoid)
- Controlled flight into terrain (CFIT)
- Fuel exhaustion
- Spatial disorientation
- Fatigue
- Medical (hypoxia, decompression, illness — AIM Chapter 8)
Reference: AIM 7-5; FAA-H-8083-25 Chapter 16 (ADM).