Southern Ocean procellariform blood and feather stable isotope data

Blood samples were centrifuged within 1-3 h to separate cells and plasma, then kept frozen at -20degreesC until freeze-dried and homogenised for analysis. Lipids were not extracted from blood cells as this is considered unnecessary. Feather samples were dried, stored in sealed plastic bags, then later ground to a fine powder in a freezer mill operating at liquid N temperature prior to analysis. C and N isotope ratios were measured by continuous-flow isotope ratio mass spectrometry, using a Carlo Erba (model NA 1500) elemental analyzer (EA) linked to a Finnigan Tracer Mat and a Costech (model ECS 4010) EA combined with a Thermo Finnigan Delta Plus XP. Three internal laboratory standards were analysed for every ten unknown samples, and measurement precision of both Delta15N and Delta13C was estimated to be less than or equal to 0.2 parts per thousand. Internal standards are routinely (once a month) calibrated against International Atomic Energy Agency and National Institute of Standards and Technology stable isotope reference materials.