Amplied Birdstrike Risk Related to Population Increases of Large Birds in North America
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Bird-aircraft collisions (bird strikes) are an increasing safety and economic concern to the civil aviation industry worldwide, costing well over $1 billion each year. To reduce risks associated with strikes, the U.S. Federal Aviation Administration has developed airworthiness standards for airframes, windshields, and engines using a single 4-lb (1.82-kg) bird mass as the maximum that must be tested for most components. We determined that 36 of the approximately 650 bird species that nest in North America have average body masses greater than 4 lbs. Of the 31 species for which population trend data were available, 24 (77%) showed population increases over the past 20-40 years, only 2 showed declines and 5 were stable. Of most importance, 13 of the 14 species with body masses over 8 lbs (3.64 kg) showed population increases. At least 294 strikes with >4-lb birds caused substantial damage to civil aircraft in the USA, 1990-2002; 30% of these strikes involved multiple birds. Over 6,022 strikes occurred at heights >1,000 feet above ground level of which at least 1,986 (33%) involved >4-lb birds. We conclude that airworthiness standards, as well as proposals to allow high-speed (>250 knots [288 miles/hour]) operations below 10,000 feet, should be reevaluated to address the threat posed by increased populations of large flocking birds. Also, increased research and development is needed in the deployment of bird-detecting radar to warn pilots of flocks of migrating birds and in techniques to make aircraft more visible to birds. Finally, wildlife biologists should increase efforts to reduce or disperse populations of these large birds in airport environments. For certain overabundant large species such as non-migratory Canada geese (Branta Canadensis), management programs may be needed to reduce populations regionally.