Low d13C signatures in pelagic seabirds: lipid ingestion as a potential source of 13C-depleted carbon in the Procellariiformes

Measuring the trophic ecology of ants using stable isotopes

“…13 C values than other body tissues in birds (Thompson et al, 2000) and fi sh (Sotiropoulos et al, 2004 15 N compared to their brood. This could be due to differences in d 15 N of resources assimilated by workers compared to brood.…”

Isotopic signatures (13C/12C;15N/14N) of blue penguin burrow soil invertebrates: carbon sources and trophic relationships

“…Variability in soil d 13 C has a multitude of causes, but within a particular site older, mineral-associated soil C has a c. 3 higher d 13 C than younger soil C fractions (Garten et al 2007). Within guano, lipid makes up 40Á50% m/m of fresh penguin guano (Zdanowski et al 2005); lipid in living seabirds has a d 13 C that is 4Á6 lower than bulk tissue (Thompson et al 2000 We conclude that blue penguin burrow invertebrates participate in food webs derived from both terrestrial and marine burrow materials, with guano playing a central role consistent with its abundance. Co-processing of feathers and guano, or soil and guano, is indicated for some taxa.…”

Parent–offspring dietary segregation of Cory’s shearwaters breeding in contrasting environments

“…We did not quantify the amount of stomach oil in the diet of chicks, but the occurrence of stomach oil during the diet sampling was of small magnitude, either at SG or at BE. Moreover, C/N ratios of shearwaters chicks were low (less than 3.5) and similar between the two colonies, suggesting that chick blood had a low lipid content (Post et al 2007) and consequently that stomach oil had no major effect on the d 13 C signatures of chicks (Thompson et al 2000). In a recent study, Richoux et al (2010) compared the diet of grayheaded albatross Thalassarche chrysostoma adults and chicks, using stomach contents and stable isotope analysis, and found no age-related differences in the d 13 C signatures of whole blood (or in the C/N ratio), despite the fact that they had collected stomach oil from a majority of the diet samples.…”

“…13 C values, since lipids are depleted in 13 C in relation to proteins or carbohydrates (Thompson et al 2000). We did not quantify the amount of stomach oil in the diet of chicks, but the occurrence of stomach oil during the diet sampling was of small magnitude, either at SG or at BE.…”

“…However, most of the mentioned studies could not assess the biological significance of the isotopic differences between adults and growing chicks (but see Cherel et al 2005a;Forero et al 2005) as isotopic fractionation differs between them, as a result of growth or nutritional stress effects (Williams et al 2007;Sears et al 2009). Additionally, the ingestion of a lipid-rich diet, as stomach oil, can deplete carbon isotopic signatures of chicks, and this has been suggested as an alternative explanation for age differences in carbon signatures (Thompson et al 2000).…”