Much of our work requires the use of satellite tags. These are fitted to birds and allow us to analyse their migration patterns and home range movements. These satellite tags use an advanced satellite system created by Argos.
The Argos satellite tracking system used has four components: the transmitters, satellites, computer data processing and a modem/Internet link. Satellite transmitter tag weight varies according to the species studied: for Peregrine and Saker Falcons they weigh around 18 to 22g. Normally around only 3.5 g of this is the electronics: the vast bulk consists of the high-rate solar-powered lithium battery. The tags themselves are attached to the falcon using a double-looped body harness made of Teflon ribbon. This has to be fitted very carefully. A short strong antenna projects outwards from the bird’s back and can often be seen in flight from some distance. Since the technology was first developed, the transmitters have become lighter and smaller; it is now possible to obtain 9g solar-powered transmitters.
Young Saker Falcon fitted with a satellite tag in Northern Mongolia
Signals are sent from the transmitters and contain information on the identity of the transmitter. Data are collected from the transmitters and then stored by the satellite until it passes over France when the information is sent down to a receiving station. In France the data are then processed and the latitude and longitude of the transmitter calculated to give the position of the bird. Click here for more information from Argos on how locations are obtained. The data can then be accessed by the end user from the Argos centre in France.
Once obtained the data can then be analysed using mapping software. Some of the units also integrate GPS capability, which means it is now possible to map both migratory and home-range movements over large distances, for long periods and across inaccessible terrain.
Click here for Argos’ extensive introduction to how satellite tracking works.