A flexible GPS tracking system for studying bird behaviour at multiple scales

Abstract

Tracking devices and bio-loggers provide cru- cial information on the ecology and behaviour of birds in their natural environment. An optimal tracking system should be lightweight, measure three-dimensional loca- tions, enable flexible measurement schemes, transmit data remotely and measure environmental variables and bio- logical parameters of the individual. Giving full consider- ation to the traits of birds and the constraints of technology, we have developed a GPS tracking system that attempts to achieve most of the aspirations of an optimal tracking system for free ranging birds without the need to recapture them. Here, we describe the design, performance and limitations of the system. We also present measurements on the tracked Lesser Black-backed Gull Larus fuscus to show how such a system can generate new opportunities for research at multiple scales. The GPS tracker weighs 12 g and includes a GPS receiver, micro-processor, 4 MB of memory for data storage, solar panel and battery. It has a tri-axial accelerometer to monitor behaviour. To maximize flexibility, it is equipped with a radio transceiver for bi- directional communication with a ground-based antenna network, which enables data to be downloaded and new measurement schemes to be uploaded remotely. The sys- tem facilitates a multi-scale approach to studying bird movement, from fine-scale movements (3-s measurement intervals) to long-distance migratory movements (intervals of 20-30 min) of the same individual. We anticipate that flexible tracking systems that enable researchers to opti- mize their measurement protocols will contribute to revo- lutionizing research on animal behaviour and ecology in the next decade.