Dataset comprises of the delta-13C and delta-15N stable isotopic information from feather samples (for 552 individuals) and the sex (assigned by DNA-analysis of blood samples for 321 individuals) of oystercatchers (Haematopus ostralegus) breeding in Iceland during the summers of 2013-2017. The Icelandic oystercatcher population contains individuals that stay in Iceland year-round and individuals that migrate to mainland Europe in the non-breeding season, and feather isotope ratios provide a means of distinguishing between these migratory behaviours (as confirmed by observations of marked individuals). These data were collected by a collaborative team from the University of Iceland, University of East Anglia (UK) and the University of Aveiro (Portugal). Full details about this dataset can be found at https://doi.org/10.5285/acbe4aa4-4ed9-428a-b633-ddd1bc119e12