Cadmium is known to be both extremely toxic and ubiquitous in natural environments. It occurs in almost all soils, surface waters and plants, and it is readily mobilized by human activities such as mining. As a result, cadmium has been named as a potential health threat to wildlife species; however, because it exists most commonly in the environment as a trace constituent, reported incidences of cadmium toxicity are rare. Here we have measured trace metals in the food web and tissues of white-tailed ptarmigan (Lagopus leucurus) in Colorado. Our results suggest that cadmium toxicity may be more common among natural populations of vertebrates than has been appreciated to date and that cadmium toxicity may often go undetected or unrecognized. In addition, our research shows that ingestion of even trace quantities of cadmium can influence not only the physiology and health of individual organisms, but also the demographics and the distribution of species.

Birds are unique among vertebrates in that they protect their eggs with rigid, calcium-rich shells. Thus, for a short period of time during the annual reproductive cycle, birds experience extraordinarily high demands for calcium. Two strategies appear to exist for meeting those temporally high demands. Some birds apparently seek out calcium-rich foods immediately prior to and during egg laying whereas others may store calcium in their skeletons over a much longer period of time, mobilizing those reserves only when they are needed for production of eggshells. In this study, we used dual energy, X-ray absorptiometry and inductively coupled plasma mass spectroscopy to monitor annual shifts in bone mineral content in the legs of White-tailed Ptarmigans (Lagopus leucurus). The study organisms were known to live on calcium-poor soils. Despite an apparent shortage of calcium in their diets, the test subjects stored substantial amounts of calcium in their leg bones in months prior to reproduction. Those stores were subsequently depleted during the egg-laying period. We suggest ability to store calcium in the skeleton may afford this species more flexibility in selecting suitable breeding habitats than would be possible otherwise.

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