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The use of stable isotopes to infer diet requires quantifying the relationship between diet and tissues and, in particular, knowing of how quickly isotopes turnover in different tissues and how isotopic concentrations of different food components change (discriminate) when incorporated into consumer tissues. We used feeding trials with wild-caught yellow-rumped warblers (Dendroica coronata) to determine δ¹⁵N and δ¹³C turnover rates for blood, δ¹⁵N and δ¹³C diet-tissue discrimination factors, and diet-tissue relationships for blood and feathers. After 3 weeks on a common diet, 36 warblers were assigned to one of four diets differing in the relative proportion of fruit and insects. Plasma half-life estimates ranged from 0.4 to 0.7 days for δ¹³C and from 0.5 to 1.7 days for δ¹⁵N . Half-life did not differ among diets. Whole blood half-life for δ¹³C ranged from 3.9 to 6.1 days. Yellow-rumped warbler tissues were …