Stable carbon and nitrogen isotope analysis of avian uric acid

Bird, Michael I., Tait, Elaine, Wurster, Christopher M., and Furness, Robert W. (2008) Stable carbon and nitrogen isotope analysis of avian uric acid. Rapid Communications in Mass Spectrometry, 22 (21). pp. 3393-3400.

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We report results obtained using a new technique developed to measure the stable-isotope composition of uric acid isolated from bird excreta (guano). Results from a diet-switch feeding trial using zebra finches suggest that the δ13C of uric acid in the guano equilibrates with the diet of the bird within 3 days of a change in diet, while the equilibration time for δ15N may be longer. The average carbon isotope discrimination between uric acid and food before the diet switch was +0.34 ± 1%(1σ) while after the diet switch this increased slightly to +0.83 ± 0.7%. (1σ). Nitrogen isotope discrimination was +1.3 ± 0.3% (1σ) and +0.3 ± 0.3% (1σ) before and after the diet switch; however, it is possible that the nitrogen isotope values did not fully equilibrate with diet switch over the course of the experiment. Analyses of other chemical fractions of the guano (organic residue after uric acid extraction and non-uric acid organics solubilised during extraction) suggest a total range of up to 3% for both δ13C and δ15N values in individual components of a single bulk guano sample. The analysis of natural samples from a range of terrestrial and marine species demonstrates that the technique yields isotopic compositions consistent with the known diets of the birds. The results from natural samples further demonstrate that multiple samples from the same species collected from the same location yield similar results, while different species from the same location exhibit a range of isotopic compositions indicative of different dietary preferences. Given that many samples of guano can be rapidly collected without any requirement to capture specimens for invasive sampling, the stable-isotope analysis of uric acid offers a new, simple and potentially powerful tool for studying avian ecology and metabolism.

Item ID: 15655
Item Type: Article (Research - C1)
ISSN: 1097-0231
Date Deposited: 25 Oct 2011 04:23
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060208 Terrestrial Ecology @ 50%
04 EARTH SCIENCES > 0402 Geochemistry > 040203 Isotope Geochemistry @ 50%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960806 Forest and Woodlands Flora, Fauna and Biodiversity @ 100%
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