Difference between lipid-extracted and non-extracted stable isotope ratios for bird egg tissue.

Specifically (A) carbon (Δδ13C), (B) nitrogen (Δδ15N) and (C) sulphur (Δδ34S) increases with ratio of carbon to nitrogen by weight (C∶N ratio) across seven aquatic bird species: ancient murrelet (ANMU), double-crested cormorant (DCCO), great blue heron (GBHE), Leach's storm-petrel (LESP), osprey (OSPR), pelagic cormorant (PECO) and rhinoceros auklet (RHAU). Also shown are results from studies listed in Table 1 (eider average with SD bars shown, Arctic birds) and best-fit habitat- and species-dependent regression models listed in Table 2. (D) Δδ13C for groups within our study compared with arithmetic lipid-correction models proposed by Post et al. [29], Ehrich et al. [33] (filled lines) and within our own study (dashed lines).