Details of the device deployment conducted on northern gannets (Sula bassana).

Devices were deployed on adult (chick-rearing) gannets (Sula bassana) to examine the potential effects of the position of extra mass on their flying behaviour. Of the 14 birds equipped with an accelerometer on the back, 8 (4 in the ‘AccBack’ group and 4 in the ‘AccBack+GPStail’ group) were included in the analysis. Another 6 birds were included in the analysis which had been fitted with accelerometers on their tail, with, and without, GPS (‘Acc+GPStail’ and ‘AccTail’ group respectively) (See Figure 1).