Fig. 7
From: Interspecific and intraspecific foraging differentiation of neighbouring tropical seabirds
a Bulk stable isotope values (δ15N and δ13C) of red blood cells (RBCs) from red-footed boobies (red, n = 59) and brown boobies (blue, n = 30) according to sex (females = triangles, males = circles). Solid lines = standard ellipse areas (SEAc). b Booby RBC stable isotope values with respect to those of fish and squid muscle tissue sampled from regurgitates. Mean (± SD) δ15N and δ13C values of prey are shown, with raw values represented by dimmed background markers. Boxes show the expected occupied area of sampled birds in prey isotope space, using mean trophic enrichment factors of 1.96‰ ∆15N and 0.32‰ ∆13C (solid boxes), and SDs of 0.79‰ ∆15N and 0.86‰ ∆13C (dotted boxes)