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Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Applied Engineering in Agriculture. 21(4): 721-727. (doi: 10.13031/2013.18559) @2005
Authors:   M. J. Delwiche, A. P. Houk, W. P. Gorenzel, T. P. Salmon
Keywords:   Alarm call, Almonds, American crow, Biosonics, Bird control, Bird damage, Corvus brachyrhynchos, Distress call

Birds can cause significant damage to a number of agricultural crops. Past studies have shown that alarm and distress calls are useful tools for repelling birds from agricultural and industrial settings, and current electronics have made this technique easier to use. A new study focused on integrating broadcast distress calls into bird management programs required the design of broadcast units with emphasis on low cost, preventing habituation, and saving power. The circuit was built around a sound recording integrated circuit with 120 s of nonvolatile memory and was set to play four 25-s distress calls, wait approximately 12 min between calls, and switch to a new call after a user-selectable number of call events (256 used in the field tests, corresponding to 3 - 4 days). An analog timer was used to set the call/wait cycle and call switching was achieved with a ripple counter. To save power, the circuit turned off every night using a voltage divider with a photoresistor to drive a power MOSFET switch. An audio-integrated circuit was used to amplify the sound signal, which was played through a trumpet speaker. Power consumption was low enough to allow operation from a 36-Ah hour battery for 2.5 months without recharging.

A number of broadcast units were built and tested in commercial almond orchards as part of a field trial to deter American crows (Corvus brachyrhynchos) from causing damage. A total of 36 broadcast units were deployed for two and a half months with no malfunctions. Some bird habituation was noted after approximately eight weeks of use. Results from the trial showed a significant reduction in damage due to distress call treatment with the broadcast units.

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