New information on roller migration
We’ve installed geolocators on rollers last summer. These small devices record the migrating route by gathering sunrise and sunset data each day.
The beginning and the finishing time of the daylight gives us the east-west position of the bird from the Greenwich 0 longitude, while the lenght of the daylight hours will provide us with latitudinal information. These devices are very light, only wheighing 0.6g, and are installed on the birds as little backpacks.
The small geolocator backpack is visible on these images (Photos: Sándor Mikulaj).
This technology has about a 150-180 km accuracy, which is a less than what satellite tagging can provide, but still a lot more information than what bird ringing ever achieved on rollers. Large areas across Africa are not populated, so there is hardly any chance for someone to spot and catch a ringed roller, and forward the data to a ringing centre.
We can get a good view of the geolocator after preening (Photo: Sándor Jakab).
The data gathered by geolocators can only be downloaded and viewed if the birds are caught again, and the devices are retrieved. Rollers are quite territorial, so it’s possible to catch the birds next year on their breeding grounds. The “SA0” colour ringed male bird has long been known to us. It was ringed in 2011 by Tamás Szitta as a chick. It’s been breeding in the area ever since. The retrieved geolocators will be sent to Switzerland for evaluation.
The "SA0" male bird with its female partner (Photo: Sándor Jakab).
Caught again: the geolocator was retrieved (Photo: Sándor Jakab).