In the winters of 2021/2022 and 2022/2023, a total of 40 yellow GPS transmitters were attached to Bewick’s Swans in Lower Saxony, of which 29 are currently active. The transmitters are equipped with a total of three solar panels, which power the transmitters. Depending on the hours of sunlight and the battery level, the transmitters record the GPS position of the swans every 5 minutes to 2 hours.

Additionally, data is recorded using acceleration sensors, allowing the behavior of the swans (such as sleeping, feeding, or flying) to be traced. If the birds are within range, the data is transmitted once a day via the GSM mobile network. However, there may be technically induced delays due to dead zones. Nevertheless, the data is stored on the transmitter and transmitted when the network is next contacted. The same applies if the birds leave the reception area of the mobile network for the breeding season.

Each transmitter also has a four-digit alphanumeric code printed on it, ending in T. This code allows the Bewick’s Swans to be individually identified in the field. In addition, all tagged Bewick’s Swans wear a yellow leg ring with the same code.