Geology topics

Peter C. McGowan

Publications and source records attributed to Peter C. McGowan.

At least 19 recordsLinked to original sources

USGS2025

Highly pathogenic avian influenza virus H5N1 in double-crested cormorants (Nannopterum auritum) of the Chesapeake Bay, USA

Double-crested Cormorants ( Nannopterum auritum ) have historically exhibited low levels of infection and antibodies to avian influenza virus (AIV). The recent global expansion of clade 2.3.4.4b A/goose/Guangdong/1/1996 highly pathogenic (HP) avian influenza virus H5N1 (HPAI H5N1) has resulted in large-scale mortalities across diverse waterbird taxa including cormorants. We sampled 32 and 29 Double-crested Cormorants breeding in the Chesapeake Bay, US, during the summers of 2023 and 2024, respectively, to assess HPAI H5N1 infection and AIV antibodies. Although no mortality was observed in the area, one bird sampled in 2023 was infected with HPAI H5N1. Additionally, 21/31 individuals in 2023 and 10/25 individuals in 2024 for which sera were collected had AIV antibodies. Based on additional testing using hemagglutination inhibition, virus neutralization, and an enzyme-linked lectin assay, 94 and 100% (2023 and 2024, respectively) of the seropositive birds tested positive for antibodies to both H5 and N1, suggesting previous infection with HPAI H5N1. These results are consistent with survival and limited clinical effects related to HPAI H5N1 infections. Furthermore, these results suggest that population immunity to HPAI H5N1 within the Chesapeake Bay might reduce future infections and potential population impacts should HP H5N1 remain on the landscape, though immunity may be waning across time. Because results are based on a single population, additional testing for both infection and antibodies as well as continued monitoring could enhance understanding of antibody persistence.

Maryland, Virginia↗

USGS2024

Dust management at an active construction area impacts monarch distribution

The North American population of monarch butterflies ( Danaus plexippus) is experiencing dramatic declines, necessitating investigations into challenges facing this species that can be resolved through management actions. For instance, dust made airborne by heavy equipment driving along a dirt road can settle on roadside vegetation, resulting in reduced use by monarchs. Dust accumulation on areas where floral nectaries such as leaves, stems, and flowers may be present could reduce the ability of pollinators, such as monarchs, to access nectar from flowering plants needed during migration. One such challenge was observed on Poplar Island, an island restoration project located in the Maryland portion of the Chesapeake Bay, USA. To determine if road watering would result in notable reductions of dust accumulation on adjacent roadside vegetation, and if such a reduction in dust would affect monarch use of treated habitat, water was applied via spraying to sections of the roadway during the 2022 fall migration period. Treatment areas where water was applied to the road were found to have significant reductions in dust accumulation ( P ≤0.001) as well as significantly higher use by monarchs ( P = 0.002), relative to non-watered control areas. While these results indicate potential utility of road watering to support monarchs at sites with high dust accumulation, numerous additional elements such as water usage and logistical constraints must also be considered. While limited in scope, these data do provide a notable proof-of-concept for managing this issue at other sites and can be built upon with further research.

Maryland↗

USGS2023

Usurpation and brooding of Least Tern (Sternula antillarum) chicks by Common Terns (Sterna hirundo)

While nest usurpation and subsequent incubation of eggs and even brooding of chicks from other species has been reported for Common Terns ( Sterna hirundo ), such behavior is considered rare. We report an observation of a Common Tern pair usurping the Least Tern ( Sternula antillarum ) nest and brooding the Least Tern chicks. While the Least Tern pair attempted to provide care for the chicks, the Common Terns displayed aggressive behavior and defended the nest. Though both species attempted to feed the chicks, no feeding events were observed due to harassment from the other species. Neither pair was observed nesting prior to or following this event, and all chicks are believed to have been lost to predation. We discuss the possible scenarios leading to the observed usurpation event, the possibility that usurpations are more common than previously believed, and the need for different monitoring methods to elucidate the causes of usurpations.

Diversity↗

USGS2023

Managing conflict between nesting common terns and herring gulls

Context: Due to the frequent depredation of eggs and chicks by herring gulls ( Larus argentatus ), numerous approaches to reduce their impact on tern colonies have been tested by wildlife managers. Previous studies have shown that the use of overhead lines presents a promising method to prevent gull nesting in tern colonies, but little work has evaluated if this approach is suitable for excluding both nesting and non-nesting gulls. Aims: The goal of this study was to explore the efficacy of a preventative approach, overhead lines, versus a more widely practiced lethal approach, shooting and trapping. Specifically, we aimed to determine if methods differ in their abilities to deter both gull nesting and presence within treatment areas and identify impacts on common tern ( Sterna hirundo ) nesting within treatment areas. Methods: We applied separate management strategies to two common tern colonies. In one colony, we removed herring gulls via shooting followed by trapping and nest removal, and in the other colony, we erected overhead lines with subsequent trapping at nests established in the treatment area. Key results: Gulls appeared to adapt quickly to shooting efforts, limiting efficacy and resulting in no significant change in abundance from pre-treatment levels ( P = 0.981). However, gull use of both the colony and surrounding brush declined significantly ( P < 0.001) following trapping and nest removal. Meanwhile, the number of gulls in the colony area declined from a pre-treatment average of 56 to only six, following the erection of overhead lines ( P < 0.001). Although six gull nests were established within the treatment area (overhead lines), they were not replaced once the parents were trapped and nests destroyed. Conclusions: Tern nesting appeared to be unaffected by any of the implemented management activities. Our data suggest that overhead lines may present an alternative to lethal control when seeking to minimise the impacts of gulls on tern colonies. Implications: The data presented in this manuscript can be used to guide managers in selecting actions to reduce conflict between gulls and breeding common terns. By using data-informed practices, managers can select the method best suited for their specific needs and priorities.

Wildlife Research↗

USGS2023

A comparison of direct & indirect survey methods for estimating colonial nesting waterbird populations

Population estimates derived from monitoring efforts can be sensitive to the survey method selected, potentially leading to biased estimates and low precision relative to true population size. While small unmanned aerial systems (UAS) present a unique opportunity to survey avian populations while limiting disturbance, relatively little is known about how this method compares with more traditional approaches. In this study we compared population estimates of Snowy ( Egretta thula ) and Cattle Egrets ( Bubulcus ibis ) in a mixed-species colony in the Chesapeake Bay (Maryland, USA) derived from UAS photo counts, flush counts, flight-line surveys, and in-colony nest counts along with the time required to derive an estimate via each approach. We found that UAS counts and flush counts produced lower pair estimates than nest counts and flight-line surveys ( P < 0.05), and required dramatically less time (x̄ = 6, 8, 84 and 90 min, respectively). These results suggest that while UAS have the potential to collect valuable survey data from breeding colonies that are hard to reach or are especially sensitive to the disturbance inherent in other methods, inherent biases should be considered and caution should be used when comparing results between survey types.

Maryland↗

USGS2022

Maintenance and dissemination of avian-origin influenza A virus within the northern Atlantic Flyway of North America

Wild waterbirds, the natural reservoirs for avian influenza viruses, undergo migratory movements each year, connecting breeding and wintering grounds within broad corridors known as flyways. In a continental or global view, the study of virus movements within and across flyways is important to understanding virus diversity, evolution, and movement. From 2015 to 2017, we sampled waterfowl from breeding (Maine) and wintering (Maryland) areas within the Atlantic Flyway (AF) along the east coast of North America to investigate the spatio-temporal trends in persistence and spread of influenza A viruses (IAV). We isolated 109 IAVs from 1,821 cloacal / oropharyngeal samples targeting mallards (Anas platyrhynchos) and American black ducks (Anas rubripes) , two species having ecological and conservation importance in the flyway that are also host reservoirs of IAV. Isolates with >99% nucleotide similarity at all gene segments were found between eight pairs of birds in the northern site across years, indicating some degree of stability among genome constellations and the possibility of environmental persistence. No movement of whole genome constellations were identified between the two parts of the flyway, however, virus gene flow between the northern and southern study locations was evident. Examination of banding records indicate direct migratory waterfowl movements between the two locations within an annual season, providing a mechanism for the inferred viral gene flow. Bayesian phylogenetic analyses provided evidence for virus dissemination from other North American wild birds to AF dabbling ducks (Anatinae), shorebirds (Charidriformes), and poultry (Galliformes). Evidence was found for virus dissemination from shorebirds to gulls (Laridae), and dabbling ducks to shorebirds and poultry. The findings from this study contribute to the understanding of IAV ecology in waterfowl within the AF.

Chesapeake Bay↗

USGS2022

Poplar Island: Understanding the development of a beneficial use restoration site

Poplar Island, like many other islands throughout the Chesapeake Bay, eroded from 460 hectares in 1847 to only 1.5 hectares by the 1990’s. However, the U.S. Army Corps of Engineers, Maryland Department of Transportation, and numerous other state and federal agencies selected this site as the location of a beneficial use project aimed at restoring remote island habitat in the Chesapeake Bay using clean dredge material. While monitoring efforts since the beginning of restoration efforts have documented extensive use of Poplar Island by numerous species across multiple taxa, these efforts have previously lacked context regarding underlying habitat patterns. However, such information is especially important on a site like Poplar Island where habitat distribution and availability can change dramatically between years due to ongoing construction efforts. To address this information gap we digitized annual aerial imagery of Poplar Island from 2006-2017 into 20 habitat classes. The resulting data layers demonstrate the transition of cells along the eastern side of the island from undeveloped cells to planted marsh cells, which matches trends seen in avian monitoring data. Similarly, our data display changes in the distribution of specific resources such as sand across the island, and how individual locations of interest such as constructed habitat islands have evolved over time. We believe that these data will provide critical insight into the factors influencing wildlife distribution patterns on Poplar Island, and will allow for the identification of management actions that may either be targeted or avoided in the planning of future beneficial use projects.

Maryland↗

USGS2022

Review of harmful algal blooms effects on birds with implications for avian wildlife in the Chesapeake Bay region

The Chesapeake Bay, along the mid-Atlantic coast of North America, is the largest estuary in the United States and provides critical habitat for wildlife. In contrast to point and non-point source release of pesticides, metals, and industrial, personal care and household use chemicals on biota in this watershed, there has only been scant attention to potential exposure and effects of algal toxins on wildlife in the Chesapeake Bay region. As background, we first review the scientific literature on algal toxins and harmful algal bloom (HAB) events in various regions of the world that principally affected birds, and to a lesser degree other wildlife. To examine the situation for the Chesapeake, we compiled information from government reports and databases summarizing wildlife mortality events for 2000 through 2020 that were associated with potentially toxic algae and HAB events. Summary findings indicate that there have been few wildlife mortality incidents definitively linked to HABs, other mortality events that were suspected to be related to HABs, and more instances in which HABs may have indirectly contributed to or occurred coincident with wildlife mortality. The dominant toxins found in the Chesapeake Bay drainage that could potentially affect wildlife are microcystins, with concentrations in water approaching or exceeding human-based thresholds for ceasing recreational use and drinking water at a number of locations. As an increasing trend in HAB events in the U.S. and in the Chesapeake Bay have been reported, additional information on HAB toxin exposure routes, comparative sensitivity among species, consequences of sublethal exposure, and better diagnostic and risk criteria would greatly assist in predicting algal toxin hazard and risks to wildlife.

Maryland, Virginia↗

USGS2022

An evaluation of transmitter effects on adult and juvenile Common Terns using leg-loop harness attachments

Marking birds with transmitters allows for the collection of data that are critical for fully understanding avian life history, but researchers must also be confident that performing such studies is as safe as possible for transmittered individuals. While much could be learned from tracking juveniles across dependency periods and first migration, doing so would require a harness-based attachment method which has not been evaluated on any species of juvenile tern. Therefore, we monitored the reproductive success and behavior of adult Common Terns ( Sterna hirundo ) and the growth and behavior of juvenile Common Terns after attaching transmitters to adults and juveniles with leg-loop harnesses made of elastic cord. We found that transmittered adults had similar reproductive success to untransmittered controls (hatching success for nests of transmittered adults = 0.553; nests of control adults = 0.665). Transmittered adults also expressed minimal behavioral differences from untransmittered controls when the groups were compared via paired treatment-control nest observations along with observations away from the nest. Transmittered juveniles had similar fledging success and growth rates to untransmittered control juveniles (fledging success for transmittered juveniles = 0.766; control juveniles = 0.817). Transmittered juveniles exhibited slight differences in behavior from controls, with increased rates of preening, although these differences did not appear to be detrimental. Finally, monitoring efforts during the breeding season following transmitter deployment found no difference in the return rate, nesting attempt rate, or hatching success rate based on treatment (P > 0.05). However, despite evidence of an individual retaining its transmitter into fall migration, no individuals retained their transmitters when resighted the following breeding season. While our results show that leg-loop harnesses made of elastic cord present a potential option for transmitter attachment to both adult and juvenile Common Terns, additional testing could provide further insight into potential long-term impacts.

Journal of Field Ornithology↗

USGS2020

Using thermal infrared cameras to detect avian chicks at various distances and vegetative coverages

Population monitoring of nesting waterbirds often involves frequent entries into the colony, but alternative methods such as local remotely sensed thermal imaging may help reduce disturbance while providing a cost-effective way to survey breeding populations. Such an approach can have high initial costs, however, which may have reduced the number of studies investigating functionality of paired thermal infrared camera and small unmanned aerial systems. Here, we take the first step of exploring the ability of two thermal infrared cameras to detect an avian chick under varying vegetative cover and distances, preceding field-mounting applications on a small unmanned aerial system. We created seven “bioboxes” to simulate a range of natural vegetation types and densities for a globally important colonial ground-nesting waterbird species, the common tern Sterna hirundo . We placed a juvenile chicken Gallus gallus (surrogate for the locally endangered common tern) in each box, and we tested two market-accessible infrared cameras (produced by FLIR Systems and Infrared Cameras, Inc.) at five elevations using a stationary boom (maximum height = 12 m). We applied computer-based digital thresholding to collected images, identifying pixels meeting one of seven threshold values. The chick was visible from at least one threshold value in 19 and 31 of 35 processed by the FLIR Systems and Infrared Cameras, respectively. Percentage of the chick identified across thresholds was generally highest at lower threshold values and elevations and decreased as elevation and threshold increased; however, the relative importance of each variable changed dramatically across bioboxes and camera types. Ability to detect a chick from processed images generally decreased with increasing elevation, and although we made no quantitative comparisons among boxes, detectability appeared greatest in images from both cameras when little or no vegetation was present. Interestingly, no single threshold value was best for all bioboxes. We observed notable differences between cameras including visual resolution of detected temperature differentials and image processing speed. Results of this controlled study show promise for the use of thermal infrared systems for detecting cryptic species in vegetation. Future research should work to combine thermal infrared and visual sensors with small unmanned aerial systems to test applicability in a mobile field application.

Journal of Fish and Wildlife Management↗

USGS2019

Promoting change in common tern (Sterna hirundo) nest site selection to minimize construction related disturbance

With dramatic declines in waterbird populations around the globe, wildlife managers have taken great care to minimize disturbance to breeding waterbird colonies. However, sometimes disturbance cannot be avoided and other actions must be considered. During the 2017 breeding season, a colony of Sterna hirundo (Common terns) were deterred from a historic nesting site due to concerns that nearby restoration related construction activities would result in continued disturbances and eventual nest abandonment. Deterrence involved placing overhead lines with flagging 1.5m above the ground surface throughout the historic nesting site early in the nesting season. Concurrently, breeding pairs of S. hirundo from the historic nesting site were encouraged to relocate to a nearby location where construction disturbance was considered minimal via a mix of social attractants (digital calls and decoys). This paired approach of deterrence and attraction was considered successful at relocating the colony, with 240 active S. hirundo nests at the relocation site. While nine nests were established in the historic colony when only diagonal and perpendicular overhead lines were present, no additional nests constructed after overhead parallel lines were added. Eggs (n=13) from these early nests were transferred into similar aged nests in the relocation colony and allowed to incubate naturally with an existing clutch. Eleven of the 13 relocated eggs successfully hatched. The success of this project shows that it is possible, with careful planning and coordination, for construction activities at habitat restoration sites to continue uninterrupted and still allow for successful nesting.

Ecological Restoration↗

USGS2019

Eviction notice: Observation of a Common Tern (Sterna hirundo) usurping an active Least Tern (Sternula antillarum) Nest

Although nest usurpation is common in some species and orders of birds, usurpation has rarely been reported for Sterninae. We observed a Sterna hirundo (Common Tern) egg in an active Sternula antillarum (Least Tern) nest with a complete clutch in a mixed-species Sterninae colony in Chesapeake Bay, MD, in May 2018. Based on observations from a game camera following usurpation, Common Terns incubated the mixed-species clutch, with no further parental care provided by the usurped Least Tern. The clutch never hatched, as the Common Terns abandoned the nest prior to the hatching. While we suspect that Common Terns usurped the Least Tern nest, alternative scenarios may explain how the Common Tern egg was documented in a Least Tern nest.

Maryland↗

USGS2018

Examination of contaminant exposure and reproduction of ospreys (Pandion haliaetus) nesting in Delaware Bay and River in 2015

A study of ospreys ( Pandion haliaetus ) nesting in the coastal Inland Bays of Delaware, and the Delaware Bay and Delaware River in 2015 examined spatial and temporal trends in contaminant exposure, food web transfer and reproduction. Concentrations of organochlorine pesticides and metabolites, polychlorinated biphenyls (PCBs), coplanar PCB toxic equivalents, polybrominated diphenyl ethers (PBDEs) and other flame retardants in sample eggs were generally greatest in the Delaware River. Concentrations of legacy contaminants in 2015 Delaware Bay eggs were lower than values observed in the 1970s through early 2000s. Several alternative brominated flame retardants were rarely detected, with only TBPH [bis(2-ethylhexyl)-tetrabromophthalate)] present in 5 of 27 samples at <5 ng/g wet weight. No relation was found between p,p ′-DDE, total PCBs or total PBDEs in eggs with egg hatching, eggs lost from nests, nestling loss, fledging and nest success. Osprey eggshell thickness recovered to pre-DDT era values, and productivity was adequate to sustain a stable population. Prey fish contaminant concentrations were generally less than those in osprey eggs, with detection frequencies and concentrations greatest in white perch ( Morone americana ) from Delaware River compared to the Bay. Biomagnification factors from fish to eggs for p,p ′-DDE and total PCBs were generally similar to findings from several Chesapeake Bay tributaries. Overall, findings suggest that there have been improvements in Delaware Estuary waterbird habitat compared to the second half of the 20th century. This trend is in part associated with mitigation of some anthropogenic contaminant threats.

Delaware Bay and River↗

USGS2018

Use of Bank Swallow (Riparia riparia) burrows as shelter by Common Tern (Sterna hirundo) chicks

The availability of shelter to avoid predation and ameliorate physiologically stressful conditions is often important to the survival of avian hatchlings. However, as changes in habitat availability force birds to nest in nontraditional locations, young must quickly adapt to using novel sources of shelter. Two Common Tern (Sterna hirundo) colonies (one vegetated and one barren) were observed during the 2017 breeding season on a remote island habitat restoration project during data collection for a larger associated study. While chicks within the vegetated colony sought shade under vegetation, those in the barren colony were frequently found under anthropogenically constructed chick shelters. The first reported instance of Common Tern chicks using Bank Swallow (Riparia riparia) burrows for shelter was also observed in the barren colony. This behavior, when paired with other similar reports, suggests that this species is able to recognize beneficial shelters, both natural and anthropogenic, and use them at a young age, an important ability if they are to successfully reproduce in atypical habitats

Maryland↗

USGS2018

Preliminary evaluation of behavioral response of nesting waterbirds to small unmanned aircraft flight

Small unmanned aircraft systems present an emerging technology with the potential to survey colonial waterbird populations while reducing disturbance in comparison to traditional ground counts. Recent research with these systems has been performed on some colonially nesting avian species; however, none have focused on wading bird species. During 2015–2016, this study tested the behavioral response of a mixed-species rookery (Cattle Egret ( Bubulcus ibis ), Snowy Egret ( Egretta thula ), Glossy Ibis ( Plegadis falcinellus ) and a groundnesting colony of Common Terns ( Sterna hirundo )) in shrub habitat to small unmanned aircraft system flights at 12 m, 15 m, 30 m, and 50 m. Even at the lowest altitudes, the birds either showed no reaction or acclimated within 60 sec of the fly-over. Conversely, physically entering the colony to conduct ground surveys resulted in all Common Terns flushing from their nests beginning when the observer was 50 m away and required significantly more time in the colony overall: ~30–60 min vs. ~3–7 min with the small unmanned aircraft system. While this study focuses only on the behavioral response of nesting birds and not comparison of count estimates, these results provide preliminary evidence that small unmanned aircraft systems provide the potential to monitor colonial nesting bird populations while minimizing disturbance to the colony.

Waterbirds↗

USGS2016

Chesapeake Bay fish–osprey ( Pandion haliaetus ) food chain: Evaluation of contaminant exposure and genetic damage

From 2011 to 2013, a large-scale ecotoxicological study was conducted in several Chesapeake Bay (USA) tributaries (Susquehanna River and flats, the Back, Baltimore Harbor/Patapsco Rivers, Anacostia/ middle Potomac, Elizabeth and James Rivers) and Poplar Island as a mid-Bay reference site. Osprey ( Pandion haliaetus ) diet and the transfer of contaminants from fish to osprey eggs were evaluated. The most bioaccumulative compounds (biomagnification factor > 5) included p,p′ -dichlorodiphenyldichloroethylene (DDE), total polychlorinated biphenyls (PCBs), total polybrominated diphenyl ethers (PBDEs), and bromodiphenyl ether (BDE) congeners 47, 99, 100, and 154. This analysis suggested that alternative brominated flame retardants and other compounds (methoxytriclosan) are not appreciably biomagnifying. A multivariate analysis of similarity indicated that major differences in patterns among study sites were driven by PCB congeners 105, 128, 156, 170/190, and 189, and PBDE congeners 99 and 209. An integrative redundancy analysis showed that osprey eggs from Baltimore Harbor/Patapsco River and the Elizabeth River had high residues of PCBs and p,p ′-DDE, with PBDEs making a substantial contribution to overall halogenated contamination on the Susquehanna and Anacostia/middle Potomac Rivers. The redundancy analysis also suggested a potential relation between PBDE residues in osprey eggs and oxidative DNA damage in nestling blood samples. The results also indicate that there is no longer a discernible relation between halogenated contaminants in osprey eggs and their reproductive success in Chesapeake Bay. Osprey populations are thriving in much of the Chesapeake, with productivity rates exceeding those required to sustain a stable population.

Chesapeake Bay↗

USGS2015

Decadal re-evaluation of contaminant exposure and productivity of ospreys ( Pandion haliaetus ) nesting in Chesapeake Bay Regions of Concern

The last large-scale ecotoxicological study of ospreys ( Pandion haliaetus ) in Chesapeake Bay was conducted in 2000-2001 and focused on U.S. EPA-designated Regions of Concern (ROCs; Baltimore Harbor/Patapsco, Anacostia/middle Potomac, and Elizabeth Rivers). In 2011-2012, ROCs were re-evaluated to determine spatial and temporal trends in productivity and contaminants. Concentrations of p,p '-DDE were low in eggs and below the threshold associated with eggshell thinning. Eggs from the Anacostia/middle Potomac Rivers had lower total PCB concentrations in 2011 than in 2000; however, concentrations remained unchanged in Baltimore Harbor. Polybrominated diphenyl ether flame retardants declined by 40%, and five alternative brominated flame retardants were detected at low levels. Osprey productivity was adequate to sustain local populations, and there was no relation between productivity and halogenated contaminants. Our findings document continued recovery of the osprey population, declining levels of many persistent halogenated compounds, and modest evidence of genetic damage in nestlings from industrialized regions.

Virginia↗

USGS2014

Exposure and food web transfer of pharmaceuticals in ospreys (Pandion haliaetus): Predictive model and empirical data

The osprey ( Pandion haliaetus ) is a well-known sentinel of environmental contamination, yet no studies have traced pharmaceuticals through the water–fish–osprey food web. A screening-level exposure assessment was used to evaluate the bioaccumulation potential of 113 pharmaceuticals and metabolites, and an artificial sweetener in this food web. Hypothetical concentrations in water reflecting “wastewater effluent dominated” or “dilution dominated” scenarios were combined with pH-specific bioconcentration factors (BCFs) to predict uptake in fish. Residues in fish and osprey food intake rate were used to calculate the daily intake (DI) of compounds by an adult female osprey. Fourteen pharmaceuticals and a drug metabolite with a BCF greater than 100 and a DI greater than 20 µg/kg were identified as being most likely to exceed the adult human therapeutic dose (HTD). These 15 compounds were also evaluated in a 40 day cumulative dose exposure scenario using first-order kinetics to account for uptake and elimination. Assuming comparable absorption to humans, the half-lives (t 1/2 ) for an adult osprey to reach the HTD within 40 days were calculated. For 3 of these pharmaceuticals, the estimated t 1/2 in ospreys was less than that for humans, and thus an osprey might theoretically reach or exceed the HTD in 3 to 7 days. To complement the exposure model, 24 compounds were quantified in water, fish plasma, and osprey nestling plasma from 7 potentially impaired locations in Chesapeake Bay. Of the 18 analytes detected in water, 8 were found in fish plasma, but only 1 in osprey plasma (the antihypertensive diltiazem). Compared to diltiazem detection rate and concentrations in water (10/12 detects, <method detection limits [MDL]–173 ng/L), there was a lower detection frequency in fish (31/233 detects, <MDL–2400 ng/L); however when present in fish, all values exceeded the maximum diltiazem concentration found in water. Diltiazem was found in all 69 osprey plasma samples (540–8630 ng/L), with 41% of these samples exceeding maximum concentrations found in fish. Diltiazem levels in fish and osprey plasma were below the human therapeutic plasma concentration (30 000 ng/L). Effect thresholds for diltiazem are unknown in ospreys at this time, and there is no evidence to suggest adverse effects. This screening-level exposure model can help identify those compounds that warrant further investigation in high-trophic level species.

Integrated Environmental Assessment and Management↗