American Kestrel Responses To Aircraft In An Airport Environment

Animal perception of risk and response to vehicle approach affect survival. We quantified American Kestrel (Falco sparverius) behavioral response to aircraft approach in an airport environment, by examining the likelihood of initiating escape, flight-initiation distance (FID), and the type of escape response. We observed 32 American Kestrel-aircraft interactions at Burke Lakefront Airport in Cleveland, Ohio, USA, from June 2015 through September 2016. American Kestrels responded to aircraft by initiating escape (i.e., FID > 0) 34% of the time, with a mean FID of 64 m and frequent (82%) returns to the same location occupied before the escape. Based on effect size estimates, the trajectory of an aircraft approach (direct vs. nondirect) was a more important determinant of whether an American Kestrel initiated escape than was the type of aircraft (propeller or piston vs. jet-powered). Assuming an average aircraft ground speed of 51.4 m/sec on landing phase, birds responded on average 1.2 sec before an aircraft was over or at the bird's position. Based on the relationship among likelihood of initiating escape, FID, and reported bird-aircraft collisions (strikes) across species studied at the same airport, American Kestrels followed a strategy of relatively low likelihood of initiating escape and short FIDs, which led to infrequent strikes. However, compared to American Kestrels, some other species that followed a similar strategy had more aircraft strikes, whereas some species with different strategies experienced similar numbers of strikes. This variation among species in escape strategies and strikes should be studied further, as it could lead to new ways of modeling bird-strike risk at airports.