title: Unusual patterns in ¹⁵N blood values after a diet switch in red knot shorebirds.
abstract: When a diet switch results in a change in dietary isotopic values, isotope ratios of the consumer's tissues will change until a new equilibrium is reached. This change is generally best described by an exponential decay curve. Indeed, after a diet switch in captive red knot shorebirds (Calidris canutus islandica), the depletion of (13)C in both blood cells and plasma followed an exponential decay curve. Surprisingly, the diet switch with a dietary (15)N/(14)N ratio (δ(15)N) change from 11.4 to 8.8 ‰ had little effect on δ(15)N in the same tissues. The diet-plasma and diet-cellular discrimination factors of (15)N with the initial diet were very low (0.5 and 0.2 ‰, respectively). δ(15)N in blood cells and plasma decreased linearly with increasing body mass, explaining about 40 % of the variation in δ(15)N. δ(15)N in plasma also decreased with increasing body-mass change (r (2)=.07). This suggests that the unusual variation in δ(15)N with time after the diet switch was due to interferences with simultaneous changes in body-protein turnover.
authors: Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands. m.w.dietz@rug.nl
authors: Maurine W
authors: MW
authors: Dietz
authors: Theunis
authors: T
authors: Piersma
authors: Anne
authors: A
authors: Dekinga
authors: Harry
authors: H
authors: Korthals
authors: Marcel
authors: M
authors: Klaassen
mesh_terms: D000818:Animals; D001835:Body Weight / Q000502:physiology; D046091:Charadriiformes / Q000097:blood* / Q000254:growth & development; D004032:Diet; D004784:Environmental Monitoring; D020387:Food Chain; D009587:Nitrogen Isotopes / Q000097:blood*; D012044:Regression Analysis; D013997:Time Factors
chemical_list: D009587:Nitrogen Isotopes