Daniel Aaron Cristol

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Mercury has contaminated rivers worldwide, with health consequences for aquatic organisms and humans who consume them. Researchers have focused on aquatic birds as sentinels for mercury. However, trophic transfer between adjacent ecosystems could lead to the export of aquatic mercury to terrestrial habitats. Along a mercury-contaminated river in Virginia,(More)
Incorporation of global climate change (GCC) effects into assessments of chemical risk and injury requires integrated examinations of chemical and nonchemical stressors. Environmental variables altered by GCC (temperature, precipitation, salinity, pH) can influence the toxicokinetics of chemical absorption, distribution, metabolism, and excretion as well as(More)
An experimental tree swallow population was established in the headwaters of the Shenandoah River, Virginia, USA to assess the accumulation and effects of mercury contamination on birds that eat emergent aquatic insects. One tributary, the South River, was contaminated with mercury before 1950. Reproductive success of swallows nesting within 50 m of this(More)
Much of the research on sublethal, adverse effects of mercury (Hg) has focused on impairment of neurological function and reproduction in fish and fish-eating vertebrates. Here we examined the associations between Hg and endocrine function (adrenocortical responses and plasma thyroid hormone concentrations) of insectivorous tree swallow nestlings adjacent(More)
Mercury is a heavy metal that has contaminated countless ecosystems throughout the world. A large body of literature has documented reproductive, physiological, and behavioral impairments associated with mercury exposure in laboratory settings, but whether and how such effects are manifest in free-living populations remains poorly understood. The purpose of(More)
Mercury is a pervasive environmental contaminant and a well-documented immunosuppressor. However, little is known about the effects of mercury contamination on health of free-living vertebrate populations. The South River in Virginia, USA was heavily contaminated with industrial mercury from 1929 to 1950, and recent studies have documented high levels of(More)
Mercury is a global pollutant that biomagnifies in food webs, placing wildlife at risk of reduced reproductive fitness and survival. Songbirds are the most diverse branch of the avian evolutionary tree; many are suffering persistent and serious population declines and we know that songbirds are frequently exposed to mercury pollution. Our objective was to(More)
Nelson's and saltmarsh sparrows (Ammodramus nelsoni and A. caudacutus) have recently been recognized as separate species, and because of their limited distributions and the susceptibility of their wetland habitats to climate change, these two new species are of conservation concern. Both species are known to bioaccumulate mercury at breeding sites in New(More)
Food-storing bird species have a larger hippocampal region than closely related non-storing species, and the avian hippocampal region appears to be involved in spatial memory for the locations of stored food. In the present study, willow tits (Parus montanus) that were at least 4 years old, had previously stored food, were trained to store and retrieve(More)
Mercury can disrupt the endocrine systems of mammals and fish, but little is known about its effects on avian hormones. The authors employed an experimental manipulation to show that methylmercury suppresses the stress-induced corticosterone response in birds, an effect previously unreported in the literature. Corticosterone regulates many normal metabolic(More)