Fig 3. (A) Nitrogen and (B) carbon isotopic signatures (median, 25–75% inter-quartile range, non-outlier range, and outliers) of birds from Cima Islet (CI; red) and Selvagem Grande (SG; blue) Islands.

Sample sizes corresponded to the amount of devices retrieved each year, with 4, 2 and 2 feather samples from SG and 3, 4 and 3 from CI, respectively in 2011, 2012 and 2013. Breeding—innermost primary feathers and, Non-breeding—eighth secondary feathers. Statistical significance: * p < 0.05, ** p < 0.01, *** p < 0.001.