Date of this Version
A suggested management plan to reduce bird numbers and bird-aircraft collisions at airports is to maintain grass 15-25 cm high. However, 3 studies conducted in the United States in 1998 indicated tall-grass management may not result in fewer birds. First, Canada geese (Branta canadensis), in a replicated experiment lasting 9 days in 6 pens in Ohio, showed no preference (P = 0.53) for short-grass (4-11 cm) over tall-grass (16-21 cm) plots. Second, we compared bird use of 8 tall- (23.3 ± 0.5 cm high, x ± SE) and 8 short- (14.3 ± 0.2) grass plots totaling 46 ha at Burke Lakefront Airport, Cleveland, Ohio on 15 days from 20 April-9 June. We found no difference (P = 0.40) in overall bird use of tall- and short-grass plots. Only 1 species, red-winged blackbirds (Agelaius phoeniceus), showed a preference (P = 0.001), with more birds (0.4 ± 0.8/ha/3-min observation) found in tall grass compared to short grass (0.1 ± 0.3). Finally, in a similar study at JFK International Airport in New York, bird observations were made on 2 unmowed (max. vegetation height of 48-130 cm) and 2 mowed (max. vegetation height of 15-25 cm) plots totaling 270 ha from 1 July-29 September. The number and species of birds hazardous to aircraft were similar in unmowed and mowed plots. The results of these studies suggest tall grass may not be an effective means of reducing bird numbers on airports. Further research, especially studies that monitor bird use of various grass types and heights over multiple seasons, is necessary to determine habitat management strategies that will reduce the number of bird species of concern on airports in North America.