Rationale

Stable hydrogen isotope (δ²H) ratios of animal tissues are useful for assessing movement and geographic origin of mobile organisms. However, it is uncertain whether heat and singeing affects feather δ²H values and thus subsequent geographic assignments. This is relevant for birds of conservation interest that are burned and killed at concentrating solar‐energy facilities that reflect sunlight to a receiving tower and generate a solar flux field.

Methods

We used a controlled experiment to test the effect of known heat loads (exposure to 200, 250 or 300°C for 1 min) on the morphology and δ²H values of feathers from two songbird species. Subsequently, we examined the effects of singeing on δ²H values of feathers from three other songbird species that were found dead in the field at a concentrating solar‐energy facility.

Results

Relative to control samples, heating caused visual morphological changes to feathers, including shriveling at 250°C and charring at 300°C. The δ²H values significantly declined by a mean of 27.8‰ in experimental samples exposed to 300°C. There was no statistically detectable difference between δ²H values of the singed and unsinged portions of field‐collected feathers from the same bird.

Conclusions

Limited singeing that did not dramatically alter the feather morphology did not substantially affect δ²H values of feathers from these songbirds. However, higher temperatures induced charring and reduced δ²H values. Therefore, severely charred feathers should be avoided when selecting feathers for δ²H‐based assessment of geographic origin.