With large expanses of open vegetation, airports serve as major attractants for numerous bird species, such as the American crow (Corvus brachyrhynchos), which can lead to high risk of bird–aircraft collision. Previous observations of large influxes of crows at the Prince George Airport (British Columbia, Canada) in July and August suggested that crows were opportunistically foraging on grasshopper (Melanoplus sp.) population eruptions in mown grass during those months. We tested whether grasshoppers were more visible (i.e., easier for crows to detect) under different grass lengths, and whether crows were preferentially attracted to these same grass lengths. Employing line transects during July to August 2010 and 2011, we detected >6 times as many grasshoppers in short-cut grass (0 to 15 cm) than in uncut grass (>30 cm). Data from 2011 also revealed that grasshopper detections by crows was significantly higher in short-cut grass than in grass left at intermediate lengths (long-cut grass [15 to 30 cm]). Crow densities also varied with grass length, with significantly more crows foraging in short-cut than long-cut or uncut grass lengths. Our results indicate that allowing the grass to grow to >15 cm could reduce the attraction of crows to the airfield and may reduce bird–aircraft collisions.
Kennedy, Laura A. and Otter, Ken A.
"Grass Management Regimes Affect Grasshopper Availability and Subsequently American Crow Activity at Airports,"
Human–Wildlife Interactions: Vol. 9
, Article 6.
Available at: http://digitalcommons.usu.edu/hwi/vol9/iss1/6