THE APPLICATION OF MOTION-SENSITIVE TRANSMITTERS TO RECORD ACTIVITY AND FORAGING PATTERNS OF OYSTERCATCHERS HAEMATOPUS-OSTRALEGUS

Time budgets are a fundamental tool in ecological research. The paper describes (a) a radiotelemetry system to monitor and quantify activity patterns in the foraging behaviour of free-living Oystercatchers, usi ng mercury switches, and (b) how to analyse such telemetric activity d ata. The radiotelemetry system enables the entire daily patterns of di fferent activities to be measured automatically. However, activity dat a recorded by radiotelemetry can be interpreted only if the pulse rate patterns characterizing different activities in each individual bird are known. Therefore, it is necessary to calibrate each transmitter by visual observations on each bird studied. After a transmitter had bee n calibrated, the system proved highly reliable for continuous ion-ter m monitoring. The system overcomes the limitations of visual observati ons, and makes more comprehensive and complete data sets available tha n can visual observations alone. The system was developed to analyse r ime budgets in Oystercatchers, but the system can be easily modified t o study other species.