Northern Prairie Wildlife Research Center
Harry L. McQuillen, Jr., Ecotoxicology & Biosystems Associates, Inc., P.O. Box 2005, Sisters, OR 97759 USA, Joseph P. Sullivan, Ecotoxicology & Biosystems Associates, Inc., 440 Hillside Avenue, Morrisville, PA 19067 USA, and Larry W. Brewer, Ecotoxicology & Biosystems Associates, Inc., P.O. Box 2005, Sisters, OR 97759 USA
A prototype automated radio telemetry system was tested in the southeastern United States to monitor avian survival and potential exposure following pesticide applications in cotton fields. The system consisted of a seven-antenna array designed to determine bird presence or absence at a field, collect signal strength data for deployed transmitters, detect bird mortality, and quantify the amount of time birds spend in a defined area. The system remained fully operational 24 hr a day throughout the three-week study period. Electrical storms interfered with the systems's ability to receive signals, but even very localized electrical storms did not harm the system. The system successfully collected continuous presence and absence data, bird mortality data, and estimated the amount of time birds spent in or near the cotton fields. However, attempts to determine accurate bird locations using signal strength as an indicator of distance from the receiving antennas to the transmitter failed.
In this study, signal strength was limited by the small size of the transmitters fitted to passerine birds, primarily northern cardinals (Cardinalis cardinalis). Transmitter strength was a limiting factor determining the size of the area the system could cover and may have been the primary factor in preventing accurate location determinations. However, the automated system was able to determine mortality using these small transmitters in the absence of mortality or activity switches. Once the system indicated a likely dead bird or lost transmitter, we were able to locate the transmitter using hand-held equipment to determine whether the bird was dead or whether the bird had lost the transmitter.
This automated system can provide 24-hr monitoring of an area to determine the amount of time radio-tagged individuals spend in the area. In addition to considerations for exposure to contaminants, this system also could be applied to habitat patch utilization questions and other ecological issues.