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Nimish B. Vyas

Publications and source records attributed to Nimish B. Vyas.

17 recordsLinked to original sources
USGS2026

Range-wide relative abundance of the Appalachian grizzled skipper ( Pyrgus centaureae wyandot ) in the Eastern United States

The U.S. Fish and Wildlife Service has designated the Pyrgus centaureae wyandot (Appalachian Grizzled Skipper [AGS]) to be at-risk, based on its declining populations and the lack of information on its status. The objective of this study was to complete range-wide surveys to locate extant AGS colonies and to quantify the number of AGS observed at each location. From 2021–24, 284 surveys were done in 25 unique (that is, distinct) counties in 8 States in the Eastern United States — Maryland, Michigan, New York, North Carolina, Ohio, Pennsylvania, Virginia, and West Virginia. We found AGS in only two counties: Alleghany County, Virginia, and Greenbrier County, West Virginia. AGS were observed 180 times in these two counties. Our results can inform U.S. Fish and Wildlife decisions about where and how future AGS conservation efforts can be implemented.

Maryland, Michigan, New York, North Carolina, Ohio↗
USGS2026

Range-wide relative abundance of Pyrgus centaureae wyandot (W.H. Edwards, 1863) (Appalachian Grizzled Skipper)

The US Fish and Wildlife Service has designated the butterfly Pyrgus centaureae wyando t (Appalachian Grizzled Skipper [AGS]) to be at-risk, based on its declining populations and the lack of information on its status. Our objective was to conduct range-wide surveys to locate extant AGS colonies and to quantify the number of AGS observed at each location. From 2021 to 2024, we conducted 284 surveys in 25 unique (i.e., distinct) counties in 8 states (Maryland, Michigan, New York, North Carolina, Ohio, Pennsylvania, Virginia, and West Virginia). We found AGS in only 2 counties: Alleghany County, VA, and Greenbrier County, WV. AGS were observed 180 times in these counties. Our results can inform US Fish and Wildlife decisions about where and how future AGS conservation efforts can be implemented.

Northeastern Naturalists↗
USGS2025

One hundred ninety-nine dead birds: Review of the scientific basis of ecological incident reporting requirements for pesticide registrants under Fifra § 6(A)(2)

The U.S. Environmental Protection Agency (EPA) regulates pesticide use in the United States. The EPA is charged by the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) with ensuring that a pesticide will not cause unreasonable adverse effects on the environment. Incident reports (documentation of exposure and injury from pesticide applications) can serve as a reality check on the pesticide registration decisions made by the EPA scientists and risk managers. The EPA collects incident reports on human, domestic animal, and ecological injury. The FIFRA section 6(a)(2) rule requires the pesticide registrant (generally, the company or other entity that wishes to market the pesticide, hereafter registrant) to submit such data to the EPA. The EPA’s ecological incident category includes injuries to aquatic (fish), terrestrial (wildlife), other non-target organisms (ONT, e.g., invertebrates) and plants. Our document focuses on the fish and wildlife ecological incidents that are submitted by registrants. We critique the application of the FIFRA section 6(a)(2) rule that controls the quality and quantity of ecological incident data that the EPA receives from registrants. We conclude that the section 6(a)(2) provisions can impede the transfer of ecological incident data from registrant to the EPA. Consequently, detailed data for many fish and wildlife incidents may never reach the EPA, and policies and decisions may be formulated in the absence of these data.

Buffalo Environmental Law Journal↗
USGS2024

Persistence of pesticide residues in weathered avian droppings

Avian droppings (combination of fecal matter and urates) provide a non-lethal and non-invasive matrix for measuring pesticide exposures. In the field, droppings may be collected days or weeks after excretion and the persistence of pesticide residues in weathered droppings is not known. Thus, we studied the effects of weathering on pesticide residues in droppings. Domestic chicken ( Gallus gallus domesticus ) hens were used as a representative species for Order Galliformes. We collected droppings from hens before they were exposed to the pesticides (reference or pre-dose droppings ). Thereafter, the hens were orally administered encapsulated wheat seeds coated with Raxil® PRO Shield (containing the active ingredients imidacloprid, prothioconazole, metalaxyl, and tebuconazole) for consecutive 7 days. During this time, their droppings were collected on days 3, 5, and 8 from the start of the exposure period (post-dose droppings ). The pre-dose and post-dose droppings were weathered for up to 30 days in autumn and spring in shrubsteppe habitat. Droppings were analyzed using HPLC coupled to triple quad LC/MS for parent compound and metabolite residues. No pesticide or its metabolite residues were detected in the weathered reference droppings. No parent pesticide compounds were detected in weathered post-dose droppings but imidacloprid metabolites, imidacloprid-5-hydroxy and imidacloprid-olefin, and the prothioconazole metabolite, desthio-prothioconazole, were detected in all post-dose weathered samples from both seasons. The active ingredients metalaxyl and tebuconazole and their metabolites were not detected in any of the samples. Our results suggest that, depending on the pesticide, its concentration, and the environmental conditions, residues of some pesticides can be detected in droppings weathered for at least 30 days. Knowledge of pesticide persistence in weathered droppings can help refine the quality and quantity of fecal samples that are collected for monitoring pesticide exposures to birds.

Environmental Research↗
USGS2022

Toxicological responses to sublethal anticoagulant rodenticide exposure in free-flying hawks

An important component of assessing the hazards of anticoagulant rodenticides to non-target wildlife is observations in exposed free-ranging individuals. The objective of this study was to determine whether environmentally realistic, sublethal first-generation anticoagulant rodenticide (FGAR) exposures via prey can result in direct or indirect adverse effects to free-flying raptors. We offered black-tailed prairie dogs ( Cynomys ludovicianus ) that had fed on Rozol® Prairie Dog Bait (Rozol, 0.005% active ingredient chlorophacinone, CPN) to six wild-caught red-tailed hawks (RTHA, Buteo jamaicensis ), and also offered black-tailed prairie dogs that were not exposed to Rozol to another two wild-caught RTHAs for 7 days. On day 6, blood was collected to determine CPN’s effects on blood clotting time. On day 7, seven of the eight RTHAs were fitted with VHF radio telemetry transmitters and the RTHAs were released the following day and were monitored for 33 days. Prothrombin time (PT) and Russell’s viper venom time confirmed that the CPN-exposed RTHAs were exposed to and were adversely affected by CPN. Four of the six CPN-exposed RTHAs exhibited ptiloerection, an indication of thermoregulatory dysfunction due to CPN toxicity, but no signs of intoxication were observed in the reference hawk or the remaining two CPN-exposed RTHAs. Of note is that PT values were associated with ptiloerection duration and frequency; therefore, sublethal CPN exposure can directly or indirectly evoke adverse effects in wild birds. Although our sample sizes were small, this study is a first to relate coagulation times to adverse clinical signs in free-ranging birds.

Colorado↗
USGS2019

Understanding and mitigating bee drownings in open feeders

Whereas open feeders are relatively inexpensive and are easily set up and maintained, they do present a drowning hazard to bees. We observed that bees feeding off the walls of the open container fell into the sugar water because of their incarnation, interactions with other bees and when shooed off the feeder walls while removing the feeder for cleaning. Twigs, angled laths and utility screen perches permitted bees to exploit more of the sugar water surface area and provided drowning bees a platform for self-rescue. Because angled laths and utility screen perches extended over the entire feeder, they offered greater feeding surface area and increased the chances that a drowning bee would quickly encounter the perches for self-rescue than twig perches. Additionally, bees were less likely to fall into the sugar water when removing the angled lath and utility screen perches from the feeders than when removing twigs. Our anecdotal observations identified three characteristics of perches that can mitigate for the drowning hazard. Perches need to: 1. Allow bees to use a greater surface area of the sugar water to reduce crowding while feeding from the container walls. 2. Encompass most of the feeder to improve the chances that drowning bees will encounter the perch and be able to rescue themselves. 3. Allow bees to quickly extricate themselves from the sugar water to minimize sugar crystallization on the bees. The information presented herein provides a practical window into the factors that lead to bee drownings and the type of mitigation that is required. It is of note that we used the three perch types to develop perch characteristics for mitigating drowning hazards. Novice researchers can apply these principles to customize perches based on their specific needs.

Bee World↗
USGS2018

Description of disparate responses of two indoor feral bee colonies

As is sometimes the case, field research does not always go according to plan. This is especially true when the research involves free-ranging animals. We recently conducted a preliminary field study that involved placing a beehive in a tent and individually releasing marked honey bees (Apis mellifera) outdoors to study their ability to locate sugar water rewards by following olfactory cues. Herein, we relay our experiences with two beehives and their disparate responses to being held in tents We believe our observations, although anecdotal, can provide much needed guidance to researchers and beekeepers who may need to temporarily hold honey bee colonies in tents or other enclosures.

Bee World↗
USGS2017

Rodenticide incidents of exposure and adverse effects on non-raptor birds

Interest in the adverse effects of rodenticides on birds has focused primarily on raptors. However, non-raptor birds are also poisoned (rodenticide exposure resulting in adverse effects including mortality) by rodenticides through consumption of the rodenticide bait and contaminated prey. A literature search for rodenticide incidents (evidence of exposure to a rodenticide, adverse effects, or exposure to placebo baits) involving non-raptor birds returned 641 records spanning the years 1931 to 2016. The incidents included 17 orders, 58 families, and 190 non-raptor bird species. Nineteen anticoagulant and non-anticoagulant rodenticide active ingredients were associated with the incidents. The number of incidents and species detected were compared by surveillance method. An incident was considered to have been reported through passive surveillance if it was voluntarily reported to the authorities whereas the report of an incident found through field work that was conducted with the objective of documenting adverse effects on birds was determined to be from active surveillance. More incidents were reported from passive surveillance than with active surveillance but a significantly greater number of species were detected in proportion to the number of incidents found through active surveillance than with passive surveillance (z = 7.61, p < 0.01). Results suggest that reliance on only one surveillance method can underestimate the number of incidents that have occurred and the number of species that are affected. Although rodenticides are used worldwide, incident records were found from only 15 countries. Therefore, awareness of the breadth of species diversity of non-raptor bird poisonings from rodenticides may increase incident reportings and can strengthen the predictions of harm characterized by risk assessments.

Science of the Total Environment↗
USGS2017

Influence of poisoned prey on foraging behavior of ferruginous hawks

We recorded 19 visits by ferruginous hawks ( Buteo regalis ) over 6 d at two black–tailed prairie dog ( Cynomys ludovicianus ) subcolonies poisoned with the rodenticide Rozol® Prairie Dog Bait (0.005% chlorophacinone active ingredient) and at an adjacent untreated subcolony. Before Rozol® application ferruginous hawks foraged in the untreated and treated subcolonies but after Rozol® application predation by ferruginous hawks was only observed in the treated subcolonies. We suggest that ferruginous hawks' preference for hunting in the treated subcolonies after Rozol® application was influenced by the availability of easy-to-capture prey, presumably due to Rozol® poisoning. The energetically beneficial behavior of favoring substandard prey may increase raptor encounters with rodenticide exposed animals if prey vulnerability has resulted from poisoning.

The American Midland Naturalist↗
USGS2013

The influence of study species selection on estimates of pesticide exposure in free-ranging birds

Field studies of pesticide effects on birds often utilize indicator species with the purpose 16 of extrapolating to other avian taxa. Little guidance exists for choosing indicator species to 17 monitor the presence and/or effects of contaminants that are labile in the environment or body, 18 but are acutely toxic, such as anticholinesterase (anti-ChE) insecticides. Use of an indicator 19 species that does not represent maximum exposure and/or effects could lead to inaccurate risk 20 estimates. Our objective was to test the relevance of a priori selection of indicator species for a 21 study on pesticide exposure to birds inhabiting fruit orchards. We used total plasma 22 cholinesterase (ChE) activity and ChE reactivation to describe the variability in anti-ChE exposure among avian species in two conventionally managed fruit orchards. Of seven 24 species included in statistical analyses, the less common species, chipping sparrow (Spizella 25 passerina), showed the greatest percentage of exposed individuals and the greatest ChE 26 depression, whereas the two most common species, American robins (Turdus migratorius) and 27 grey catbirds (Dumatella carolinensis), did not show significant exposure. Due to their lower 28 abundance, chipping sparrows would have been an unlikely choice for study. Our results show 29 that selection of indicator species using traditionally accepted criteria such as abundance and 30 ease of collection may not identify species that are at greatest risk. Our efforts also demonstrate 31 the usefulness of conducting multiple-species pilot studies prior to initiating detailed studies on 32 pesticide effects. A study such as ours can help focus research and resources on study species 33 that are most appropriate.

Environmental Management↗
USGS2013

Evidence of songbird intoxication from Rozol application at a black-tailed prairie dog colony

Concerns about avian poisonings from anticoagulant rodenticides have traditionally focused on secondary poisoning of raptors exposed by feeding on contaminated mammalian prey. However, ground foraging songbirds can be directly poisoned from operational applications of the anticoagulant rodenticide Rozol® (0.005% chlorophacinone, active ingredient) applied as a grain bait, at black-tailed prairie dog Cynomys ludovicianus colonies. A dead western meadowlark Sturnella neglecta recovered from the study prairie dog colony displayed hemorrhaging in brain and pectoral muscle tissue, and it contained chlorophacinone residue concentrations of 0.59 and 0.49 µg/g (wet weight) in the liver and intestinal contents, respectively. Chlorophacinone residues from two Rozol-colored songbird droppings found at the study colony were 0.09 and 0.46 µg/g (wet weight). The timing of the meadowlark mortality and the occurrence of discolored droppings show that songbird exposure and poisoning can occur weeks after a Rozol application.

Colorado↗
USGS2013

Untested pesticide mitigation requirements: ecological, agricultural, and legal implications

Every pesticide sold in the United States must have a U.S. Environmental Agency approved label on its container. The label provides directions for the pesticide’s use and is legally enforceable under the Federal Insecticide, Fungicide and Rodenticide Act. For a pesticide with high ecological risks, mitigation statements may be included on the label to reduce the pesticide’s risks and to support its registration. Many mitigation mandates are easy to implement and are effective, however, at times, well-intentioned but novel and untested mitigation requirements, though theoretically sound, may not be perceived by the pesticide users to be practical under operational settings. Courts of law recognize the pesticide label as a legal document, therefore it is imperative that the label mitigation mandates be achievable. I use the rodenticide Rozol label to illustrate how an untested risk mitigation mandate may be considered too burdensome by pesticide users whereby the mitigation action may not be implemented in the field, resulting in label violation and unreasonable risks to the environment.

Drake Journal of Agricultural Law↗
USGS2012

Chlorophacinone residues in mammalian prey at a black-tailed prairie dog colony

Black-tailed prairie dogs (BTPDs), Cynomys ludovicianus, are an important prey for raptors; therefore, the use of the rodenticide Rozol (0.005% chlorophacinone active ingredient) to control BTPDs raises concern for secondary poisonings resulting from the consumption of contaminated prey by raptors. In the present study, the authors observed Rozol exposure and adverse effects to mammalian prey on 11 of 12 search days of the study. Mammalian hepatic chlorophacinone residues ranged from 0.44 to 7.56 µg/g. Poisoned prey availability was greater than previously reported.

Environmental Toxicology and Chemistry↗
USGS2012

Critique on the use of the standardized avian acute oral toxicity test for first generation anticoagulant rodenticides

Avian risk assessments for rodenticides are often driven by the results of standardized acute oral toxicity tests without regards to a toxicant's mode of action and time course of adverse effects. First generation anticoagulant rodenticides (FGARs) generally require multiple feedings over several days to achieve a threshold concentration in tissue and cause adverse effects. This exposure regimen is much different than that used in the standardized acute oral toxicity test methodology. Median lethal dose values derived from standardized acute oral toxicity tests underestimate the environmental hazard and risk of FGARs. Caution is warranted when FGAR toxicity, physiological effects, and pharmacokinetics derived from standardized acute oral toxicity testing are used for forensic confirmation of the cause of death in avian mortality incidents and when characterizing FGARs' risks to free-ranging birds.

Human and Ecological Risk Assessment↗
USGS2005

From the Field: Carbofuran detected on weathered raptor carcass feet

The cause of death for raptors poisoned at illegal carbofuran-laced predator baits is often not confirmed because the carcass matrices that are conventionally analyzed are not available due to decomposition and scavenging. However, many such carcasses retain intact feet that may have come into contact with carbofuran. Eastern screech owls ( Otus asio ) were exposed to carbofuran via simulated predator baits. Detection of carbofuran from owl feet weathered for 28 days demonstrated the temporal reliability of using feet during a forensic investigation. Raptor carcasses previously not submitted for residue analysis because of a lack of the conventional matrices may now be salvaged for their feet.

Wildlife Society Bulletin↗
USGS1996

Toxicity of fire retardant chemicals and fire suppressant foams to vertebrate and invertebrate wildlife species

Under laboratory conditions, acute single-dose oral toxicity tests (LD50) were conducted with three fire retardant chemicals (Fire-Trol GTS-R, Phos-Chek D75-F, and Fire-Trol LCG-R) and two fire suppressant foams (Silv-Ex and Phos-Chek WD-881) to determine effects on adult northern bobwhite, American kestrel, red-winged blackbird, and white-footed mouse. In addition, earthworms were exposed (LC50) for 14 days in treated soil. In general, no toxic responses were evident. For northern bobwhite, the LD50 for all five chemicals was >2000 mg a.l./kg of body mass. American kestrels regurgitated all chemicals except Silv-ex; LD50s all exceeded 2000 mg/kg. The LD50 for red-winged blackbird was also >2000 mg/kg for all chemicals except Fire-Trol GTS-R which is currently undergoing further testing. In addition, the LD50 for white-footed mouse was >2000 mg/kg for Phos-Chek D75F. The 14-day LC50 for earthworms was >1000 ppm for all chemicals. Therefore, we concluded that these retardants and foams do not pose an acute hazard to adult birds, mammals, or earthworms. However, ecological studies to evaluate the potential effects of these formulations on vertebrate behavior and population dynamics are in progress.

Book chapter↗