Fig. 2
Changes in weight of tracking devices over study years. a Average weight in grams of tracking devices used in study years with coloured areas delineating the region between maximum and minimum weight, for radio transmitters (red), PTTs (green) and GPS devices (blue). b Average weight of tracking devices as a fraction of the weight of the bird on which it was deployed, with the coloured area delineating the region between minimum and maximum fraction of weight