Geology topics

Joshua T. Ackerman

Publications and source records attributed to Joshua T. Ackerman.

At least 73 records · Page 4Linked to original sources

USGS2020

Good prospects: High-resolution telemetry data suggests novel brood-site selection behavior in waterfowl

Breeding success should increase with prior knowledge of the surrounding environment, which is dependent upon an animal’s ability to evaluate habitat. Prospecting for nesting locations and migratory stop-over sites are well-established behaviors among bird species. We assessed whether ducks in Suisun Marsh, California, USA, a brackish marsh, prospect for suitable wetlands in the week prior to brooding. K-means cluster analyses grouped 29 mallard and gadwall hens into 3 groups. One group (n=13) demonstrated evidence of brood site prospecting with fewest and latest pre-brooding wetland visits. Of these hens, seven visited their future brood pond an average of 1.14 times and only shortly before brooding (1.29 days), obtaining current information on habitat suitability. For the remaining 6 hens, we did not detect a brooding wetland visit which may be due to data limitations or the need to prospect the specific brood pond was precluded by having acquired sufficient familiarity with the wetland habitat during nest breaks in adjacent wetlands. The second identified group of hens (n=11) visited the brooding wetland most frequently (on 4.55 days), farther in advance (5.27 days), with the fewest unique wetland visits and the earliest brooding date (May 26). The final group of hens (n=5) were the latest to brood (Jun 21) and visited the most wetlands, possibly due to less water or more broods present across the landscape. Brood ponds were always farther from the nest than the nearest ponds indicating that habitat suitability or presence of conspecifics is more important to brood-site selection. Prospecting provides hens with knowledge about current habitat conditions and allows them to ‘crowdsource’ public information regarding use of that habitat by other brooding hens. Prospecting may therefore, benefit ducks inhabiting ephemeral habitats like those within Suisun Marsh, where brood habitat is limited, and water cover changes rapidly during the breeding season.

California↗

USGS2020

Social attraction used to establish Caspian tern nesting colonies in San Francisco Bay

Conservation of colonial waterbird breeding populations often includes restoring historic nesting habitat or establishing new nesting habitat in protected areas. However, colonization of new or restored nesting habitat may be hindered by the lack of social cues from nesting conspecifics to attract prospecting birds. Social attraction, whereby decoys and colony sound recordings are used to mimic active nesting colonies, has been used successfully to establish waterbird nesting colonies throughout the world. We constructed islands, modified the substrate so that it was attractive to nesting Caspian terns (Hydroprogne caspia), and then used social attraction to establish nesting colonies within two managed ponds in San Francisco Bay, California where Caspian terns had not previously nested. During the 2015–2017 breeding seasons, we deployed decoys of adult Caspian terns, broadcasted colony sound recordings, and monitored Caspian tern response. Caspian terns formed nesting colonies within weeks of social attraction deployment at each of the two ponds in 2015, and the size of these colonies increased in each subsequent year of the study. In 2017, the final year of the study, we estimated a minimum of 501 breeding pairs between the two colonies, making them two of the three largest Caspian tern colonies in the San Francisco Bay estuary. In total, these two colonies produced 1343 nests and 531 fledglings over the three-year study period. Nest densities were low (mean: 0.29 nests/m2 of active colony area) compared to other studies, and greater than 80% of the modified island habitat remained unused by nesting Caspian terns in 2017, suggesting that there is additional space for future colony growth. The successful establishment of two of the largest Caspian tern nesting colonies in the San Francisco Bay estuary in just three years demonstrates the potential of using island construction and habitat modifications, combined with social attraction measures to establish waterbird nesting colonies.

California↗

USGS2020

Methylmercury exposure in wildlife: A review of the ecological and physiological processes affecting contaminant concentrations and their interpretation

Exposure to methylmercury (MeHg) can result in detrimental health effects in wildlife. With advances in ecological indicators and analytical techniques for measurement of MeHg in a variety of tissues, numerous processes have been identified that can influence MeHg concentrations in wildlife. This review presents a synthesis of theoretical principals and applied information for measuring MeHg exposure and interpreting MeHg concentrations in wildlife. Mercury concentrations in wildlife are the net result of ecological processes influencing dietary exposure combined with physiological processes that regulate assimilation, transformation, and elimination. Therefore, consideration of both physiological and ecological processes should be integrated when formulating biomonitoring strategies. Ecological indicators, particularly stable isotopes of carbon, nitrogen, and sulfur, compound-specific stable isotopes, and fatty acids, can be effective tools to evaluate dietary MeHg exposure. Animal species differ in their physiological capacity for MeHg elimination, and animal tissues can be inert or physiologically active, act as sites of storage, transformation, or excretion of MeHg, and vary in the timing of MeHg exposure they represent. Biological influences such as age, sex, maternal transfer, and growth or fasting are also relevant for interpretation of tissue MeHg concentrations. Wildlife tissues that represent current or near-term bioaccumulation and in which MeHg is the predominant mercury species (such as blood and eggs) are most effective for biomonitoring ecosystems and understanding landscape drivers of MeHg exposure. Further research is suggested to critically evaluate the use of keratinized external tissues to measure MeHg bioaccumulation, particularly for less-well studied wildlife such as reptiles and terrestrial mammals. Suggested methods are provided to effectively use wildlife for quantifying patterns and drivers of MeHg bioaccumulation over time and space, as well as for assessing the potential risk and toxicological effects of MeHg on wildlife.

Science of the Total Environment↗

USGS2020

Ecological insights from three decades of animal movement tracking across a changing Arctic

The Arctic is entering a new ecological state, with alarming consequences for humanity. Animal-borne sensors offer a window into these changes. Although substantial animal tracking data from the Arctic and subarctic exist, most are difficult to discover and access. Here, we present the new Arctic Animal Movement Archive (AAMA), a growing collection of more than 200 standardized terrestrial and marine animal tracking studies from 1991 to the present. The AAMA supports public data discovery, preserves fundamental baseline data for the future, and facilitates efficient, collaborative data analysis. With AAMA-based case studies, we document climatic influences on the migration phenology of eagles, geographic differences in the adaptive response of caribou reproductive phenology to climate change, and species-specific changes in terrestrial mammal movement rates in response to increasing temperature.

Science↗

USGS2020

Nesting ecology of White-faced Ibis (Plegadis chihi) in Great Salt Lake, Utah

We studied the nesting ecology of White-faced Ibis ( Plegadis chihi ) at 3 sites within the Bear River Migratory Bird Refuge, Great Salt Lake, Utah, USA. Ibises built nests in small mounds (mean height = 14.4 ± 4.3 cm) above shallow water (mean depth = 12.0 ± 6.6 cm) located within patchy vegetation (mean percent vegetative cover = 17.2 ± 17.8% vegetative cover) with mean vegetation height of 31.7 ± 9.8 cm. White-faced Ibis typically laid a clutch of 3 or 4 eggs (mean clutch size = 3.08 ± 0.76) and initiated nests over a 50 d period between 24 April 2012 and 12 June 2012. Mean nest success was 38% (95% CI: 31–45%) and hatching success of eggs from successful nests was 76 ± 26%. Although most of the breeding parameters estimated for White-faced Ibis nesting in Utah were comparable to other populations in Oregon and Idaho (USA), nest success may now be lower than has been historically documented.

Utah↗

USGS2019

Synthesis of maternal transfer of mercury in birds: Implications for altered toxicity risk

Maternal transfer is the predominant route of methylmercury (MeHg) exposure to offspring. We reviewed and synthesized published and unpublished data on maternal transfer of MeHg in birds. Using paired samples of females’ blood (n=564) and their eggs (n=1814) from 26 bird species in 6 taxonomic orders, we conducted a meta-analysis to evaluate whether maternal transfer of MeHg to eggs differed among species and caused differential toxicity risk to embryos. Total mercury (THg) concentrations in eggs increased with maternal blood THg concentrations; however, the proportion of THg transferred from females to their eggs differed among bird taxa and with maternal THg exposure. Specifically, a smaller proportion of maternal THg was transferred to eggs with increasing female THg concentrations. Additionally, the proportion of THg that was transferred to eggs at the same maternal blood THg concentration differed among taxonomic orders, with waterfowl (Anseriformes) transferring up to 382% more THg into their eggs than songbirds (Passeriformes). We provide equations to predict THg concentrations in eggs using female blood THg concentrations, and vice versa, which may help translate toxicity benchmarks across tissues and life stages. Our results indicate that toxicity risk of MeHg can vary among bird taxa due to differences in the maternal transfer of MeHg to offspring.

Environmental Science & Technology↗

USGS2019

Wintering in the western subarctic pacific increases mercury contamination of Red-legged Kittiwakes

Marine methylmercury concentrations vary geographically and with depth, exposing organisms to different mercury levels in unique habitats. Red-legged kittiwakes (Rissa brevirostris), a specialist predator, forage on fish and invertebrates from the mesopelagic zone, a part of the ocean with elevated methylmercury concentrations. We used kittiwakes as bioindicators of MeHg concentrations in remote mesopelagic systems by examining how wintering distribution and habitat affected kittiwakes’ mercury exposure. In 2011-2017, we sampled winter-grown feathers on St. George Island, Alaska, from birds equipped with geolocation loggers. We measured total mercury (THg) and nitrogen stable in nape and head feathers grown during winter, respectively. THg concentration of kittiwake nape feathers averaged 4.61 ± 0.97 µg/g dry weight. Hierarchical cluster analysis was used to classify winter habitats with remotely sensed environmental variables along each bird’s track. Five habitat clusters were identified. Birds that spent more time in the Western Subarctic Gyre and those that wintered further south had elevated THg concentrations. In contrast to THg, trophic level varied annually but did not show strong spatial patterns. Our results documented spatial variability in THg exposure based on the oceanic wintering locations of red-legged kittiwakes and highlight their use as a bioindicator of MeHg across ocean basins.

Alaska↗

USGS2019

Wetland management strategy to reduce mercury export in water and bioaccumulation in fish

Wetland environments provide numerous ecosystem services but also facilitate methylmercury (MeHg) production and bioaccumulation. We developed a wetland‐management technique to reduce MeHg concentrations in wetland fish and water. We physically modified seasonal wetlands by constructing open‐ and deep‐water treatment cells at the downstream end of seasonal wetlands to promote naturally occurring MeHg‐removal processes. We assessed the effectiveness of reducing mercury (Hg) concentrations in surface water and western mosquitofish that were caged at specific locations within 4 control and 4 treatment wetlands. Methylmercury concentrations in wetland water were successfully decreased within treatment cells during only the third year of study; however, treatment cells were not effective for reducing total Hg concentrations. Furthermore, treatment cells were not effective for reducing total Hg concentrations in wetland fish. Mercury concentrations in fish were not correlated with total Hg concentrations in filtered, particulate, or whole water; and the slope of the correlation with water MeHg concentrations differed between months. Fish total Hg concentrations were weakly correlated with water MeHg concentrations in April when fish were introduced into cages but were not correlated in May when fish were retrieved from cages. Fish total Hg concentrations were greater in treatment wetlands than in control wetlands the year after the treatment wetlands’ construction but declined by the second year. During the third year, fish total Hg concentrations increased in both control and treatment wetlands after an unexpected regional flooding event. Overall, we found limited support for the use of open‐ and deep‐water treatment cells at the downstream end of wetlands to reduce MeHg concentrations in water but not fish. We suggest that additional evaluation over a longer period of time is necessary.

Environmental Toxicology and Chemistry↗

USGS2019

San Francisco Bay triennial bird egg monitoring program for contaminants, California—2018

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP), administered by the San Francisco Estuary Institute, is a large-scale effort to monitor contaminant trends in water, sediment, fish, and birds throughout San Francisco Bay (San Francisco Estuary Institute, 2016). As part of the RMP and the U.S. Geological Survey (USGS) long-term Wildlife Contaminants Program, the USGS samples doublecrested cormorant ( Phalacrocorax auritus ) and Forster’s tern ( Sterna forsteri ) eggs throughout the San Francisco Bay approximately every 3 years to assess temporal trends in contaminant concentrations. This sampling has previously been carried out by USGS in 2009, 2012, and 2016. This document summarizes egg collections for 2018, as well as mercury concentrations in Forster’s tern eggs on an individual egg basis. These data are available in a USGS data release (Ackerman and others, 2019).

California↗

USGS2019

Sitting ducklings: Timing of hatch, nest departure, and predation risk for dabbling duck broods

For ground‐nesting waterfowl, the timing of egg hatch and duckling departure from the nest may be influenced by the risk of predation at the nest and en route to wetlands and constrained by the time required for ducklings to imprint on the hen and be physically able to leave the nest. We determined the timing of hatch, nest departure, and predation on dabbling duck broods using small video cameras placed at the nests of mallard ( Anas platyrhynchos ; n = 26), gadwall ( Mareca strepera ; n = 24), and cinnamon teal ( Anas cyanoptera ; n = 5). Mallard eggs began to hatch throughout the day and night, whereas gadwall eggs generally started to hatch during daylight hours (mean 7.5 hr after dawn). Among all species, duckling departure from the nest occurred during daylight (98%), and 53% of hens typically left the nest with their broods 1–4 hr after dawn. For mallard and gadwall, we identified three strategies for the timing of nest departure: (a) 9% of broods left the nest the same day that eggs began to hatch (6–12 hr later), (b) 81% of broods left the nest the day after eggs began to hatch, and (c) 10% of broods waited 2 days to depart the nest after eggs began to hatch, leaving the nest just after the second dawn (27–42 hr later). Overall, eggs were depredated at 10% of nests with cameras in the 2 days prior to hatch and ducklings were depredated at 15% of nests with cameras before leaving the nest. Our results suggest that broods prefer to depart the nest early in the morning, which may best balance developmental constraints with predation risk both at the nest and en route to wetlands.

Ecology and Evolution↗

USGS2019

Mercury concentrations vary within and among individual bird feathers: A critical evaluation and guidelines for feather use in mercury monitoring programs

Feathers are widely used to represent mercury contamination in birds. Yet, few recommendations exist that provide guidance for using bird feathers in mercury monitoring programs. We conducted a literature review and 5 experiments to show that mercury concentrations vary substantially within (vane >100% higher than calamus) and among (>1000%) individual feathers from the same bird. We developed a research tool and guidelines for using bird feathers for mercury studies based on three components: 1) variability of feather mercury concentrations within an individual bird (coefficient of variation [CV]), 2) desired accuracy of the measured mercury concentration, and 3) feather and bird mass. Our results suggest a general rule that if the goal is to limit analytical and processing costs by using whole feathers in only one sample boat, then to achieve an accuracy within 10% of a bird’s overall average feather mercury concentration a bird with a CV≤10% must be <190 g (size of large shorebird). To achieve an accuracy within 20%, a bird with a CV≤10% must be <920 g (size of large duck). When >1 sample boat is needed to fit the required number of feathers to achieve the desired accuracy, results suggest homogenizing feathers and analyzing an aliquot of ≥20 mg for mercury. This study indicates increasing the number of feathers typically used per bird to assess mercury concentrations.

Environmental Toxicology and Chemistry↗

USGS2019

Mercury exposure and altered parental nesting behavior in a wild songbird

Methylmercury is a neurotoxin and endocrine disruptor and may impair avian reproduction directly through embryotoxicity or by altering parental care behaviors. We studied mercury exposure and incubation behavior of free-living tree swallows (Tachycineta bicolor) nesting in artificial nest boxes. Using small temperature dataloggers, we measured incubation constancy (the proportion of each day the female spent incubating eggs), the number of incubation recesses taken per day, and the duration of incubation recesses. We also assessed maternal mercury exposure by measuring mercury concentrations in both blood and eggs. Females with higher mercury concentrations exhibited lower incubation constancy, took more frequent and shorter incubation recesses, and were more likely to take incubation recesses that caused nest temperature decreases that were likely to slow embryonic development. Overall, females that laid eggs with the highest observed mercury concentration (0.53 μg/g fww) spent an average of 12% less time incubating their eggs over the 14-day incubation period than females that laid eggs with the lowest mercury concentration (0.07 μg/g fww). Because less time spent incubating can lower egg temperatures, slow embryonic development, and potentially lengthen the incubation period, these results suggest that environmentally relevant mercury concentrations may negatively influence reproduction by altering parental nesting behaviors of wild songbirds

Environmental Science & Technology↗

USGS2019

GPS tracking data reveals daily spatio-temporal movement patterns of waterfowl

Background Spatio-temporal patterns of movement can characterize relationships between organisms and their surroundings, and address gaps in our understanding of species ecology, activity budgets, bioenergetics, and habitat resource management. Highly mobile waterfowl, which can exploit resources over large spatial extents, are excellent models to understand relationships between movements and resource usage, landscape interactions and specific habitat needs. Methods We tracked 3 species of dabbling ducks with GPS-GSM transmitters in 2015–17 to examine fine-scale movement patterns over 24 h periods (30 min interval), dividing movement pathways into temporally continuous segments and spatially contiguous patches. We quantified distances moved, area used and time allocated across the day, using linear and generalized linear mixed models. We investigated behavior through relationships between these variables. Results Movements and space-use were small, and varied by species, sex and season. Gadwall ( Mareca strepera ) generally moved least (FFDs: 0.5–0.7 km), but their larger foraging patches resulted from longer within-area movements. Pintails ( Anas acuta ) moved most, were more likely to conduct flights > 300 m, had FFDs of 0.8–1.1 km, used more segments and patches per day that they revisited more frequently, resulting in the longest daily total movements. Females and males differed only during the post-hunt season when females moved more. 23.6% of track segments were short duration (1–2 locations), approximately 1/3 more than would be expected if they occurred randomly, and were more dispersed in the landscape than longer segments. Distance moved in 30 min shortened as segment duration increased, likely reflecting phases of non-movement captured within segments. Conclusions Pacific Flyway ducks spend the majority of time using smaller foraging and resting areas than expected or previously reported, implying that foraging areas may be highly localized, and nutrients obtainable from smaller areas. Additionally, movement reductions over time demonstrates behavioral adjustments that represent divergent energetic demands, the detection of which is a key advantage of higher frequency data. Ducks likely use less energy for movement than currently predicted and management, including distribution and configuration of essential habitat, may require reconsideration. Our study illustrates how fine-scale movement data from tracking help understand and inform various other fields of research.

California↗

USGS2019

Feather mercury concentrations in North American raptors sampled at migration monitoring stations

We assessed total mercury (THg) concentrations in breast feathers of diurnal North American raptors collected at migration monitoring stations. For 9 species in the Pacific Flyway, we found species and age influenced feather THg concentrations whereas sex did not. Feather THg concentrations µg/g dry weight (dw) averaged (least-squared mean±standard error) higher for raptors that generally consume >75% avian prey (sharp-shinned hawk Accipiter striatus: n=113; 4.35±0.45 µg/g dw, peregrine falcon Falco peregrinus: n=12; 3.93±1.11 µg/g dw, Cooper’s hawk Accipiter cooperii: n=20; 2.35±0.50 µg/g dw, and merlin Falco columbarius: n=59; 1.75±0.28 µg/g dw) than for raptors that generally consume <75% avian prey (northern harrier Circus hudsonius: n=112; 0.75±0.10 µg/g dw, red-tailed hawk Buteo jamaicensis: n=109; 0.56±0.06 µg/g dw, American kestrel Falco sparverius: n=16; 0.57±0.14 µg/g dw, prairie falcon Falco mexicanus: n=10; 0.41±0.13 µg/g dw) except for red-shouldered hawks Buteo lineatus: n=10; 1.94±0.61 µg/g dw. Feather THg concentrations spanning 13-years (2002-2014) in the Pacific Flyway differed among 3 species, where THg increased for juvenile northern harrier, decreased for adult red-tailed hawk, and showed no trend for adult sharp-shinned hawk. Mean feather THg concentrations in juvenile merlin were greater in the Mississippi Flyway (n=56; 2.14±0.18 µg/g dw) than those in the Pacific Flyway (n=49; 1.15±0.11 µg/g dw) and Intermountain Flyway (n=23; 1.14±0.16 µg/g dw), and Atlantic Flyway (n=38; 1.75±0.19 µg/g dw) averaged greater than the Pacific Flyway. Our results indicate that raptor migration monitoring stations provide a cost-effective sampling opportunity for biomonitoring environmental contaminants within and between distinct migration corridors and across time.

Ecotoxicology↗

USGS2019

Surveillance for highly pathogenic influenza A viruses in California during 2014–2015 provides insights into viral evolutionary pathways and the spatiotemporal extent of viruses in the Pacific Americas Flyway

We used surveillance data collected in California before, concurrent with, and subsequent to an outbreak of highly pathogenic (HP) clade 2.3.4.4 influenza A viruses (IAVs) in 2014–2015 to (i) evaluate IAV prevalence in waterfowl, (ii) assess the evidence for spill-over infections in marine mammals and (iii) genetically characterize low-pathogenic (LP) and HP IAVs to refine inference on the spatiotemporal extent of HP genome constellations and to evaluate possible evolutionary pathways. We screened samples from 1496 waterfowl and 1142 marine mammals collected from April 2014 to August 2015 and detected IAV RNA in 159 samples collected from birds ( n = 157) and pinnipeds ( n = 2). HP IAV RNA was identified in three samples originating from American wigeon ( Anas americana ). Genetic sequence data were generated for a clade 2.3.4.4 HP IAV-positive diagnostic sample and 57 LP IAV isolates. Phylogenetic analyses revealed that the HP IAV was a reassortant H5N8 virus with gene segments closely related to LP IAVs detected in mallards ( Anas platyrhynchos ) sampled in California and other IAVs detected in wild birds sampled within the Pacific Americas Flyway. In addition, our analysis provided support for common ancestry between LP IAVs recovered from waterfowl sampled in California and gene segments of reassortant HP H5N1 IAVs detected in British Columbia, Canada and Washington, USA. Our investigation provides evidence that waterfowl are likely to have played a role in the evolution of reassortant HP IAVs in the Pacific Americas Flyway during 2014–2015, whereas we did not find support for spill-over infections in potential pinniped hosts.

Emerging Microbes & Infections↗

USGS2019

Mercury contamination in resident and migrant songbirds and potential effects on body condition

Methlymercury is a significant risk to environmental health globally. We examined the ecological drivers of methylmercury bioaccumulation in songbirds and its effect on body condition while experimentally removing the potentially confounding and predominant effects of site and habitat. We measured blood and feather mercury concentrations and body condition in nearly 1200 individuals representing resident or migrant songbirds of 52 species and 5 foraging guilds. Songbird mercury concentrations differed among species, foraging guilds, residency status, dates, and ages, but not sexes. Blood mercury concentrations 1) ranged from 0.003 in house finch to 0.85 μg/g ww in American robin, 2) were 125 times greater in insectivores than granivores and 3.6 times greater in insectivores than omnivores, 3) were 3.3 times greater in summer residents than in migrating songbirds, 4) increased by 25% throughout spring and summer, and 5) were 45% higher in adults than juveniles. Songbird mercury concentrations were negatively correlated with body condition, with blood mercury concentrations decreasing by 44% and 34% over the range of standardized body masses and fat scores, respectively. Our results highlight the importance of foraging and migration ecology in determining methylmercury contamination in birds, and the potential for reduced body condition with methylmercury exposure in songbirds.

Environmental Pollution↗

USGS2019

Current state of knowledge on biological effects from contaminants on arctic wildlife and fish

Since the last Arctic Monitoring and Assessment Programme (AMAP) effort to review biological effects of the exposure to organohalogen compounds (OHCs) in Arctic biota, there has been a considerable number of new Arctic effect studies. Here, we provide an update on the state of the knowledge of OHC, and also include mercury, exposure and/or associated effects in key Arctic marine and terrestrial mammal and bird species as well as in fish by reviewing the literature published since the last AMAP assessment in 2010. We aimed at updating the knowledge of how single but also combined health effects are or can be associated to the exposure to single compounds or mixtures of OHCs. We also focussed on assessing both potential individual as well as population health impacts using population-specific exposure data post 2000. We have identified quantifiable effects on vitamin metabolism, immune functioning, thyroid and steroid hormone balances, oxidative stress, tissue pathology, and reproduction. As with the previous assessment, a wealth of documentation is available for biological effects in marine mammals and seabirds, and sentinel species such as the sledge dog and Arctic fox, but information for terrestrial vertebrates and fish remain scarce. While hormones and vitamins are thoroughly studied, oxidative stress, immunotoxic and reproductive effects need further investigation. Depending on the species and population, some OHCs and mercury tissue contaminant burdens post 2000 were observed to be high enough to exceed putative risk threshold levels that have been previously estimated for non-target species or populations outside the Arctic. In this assessment, we made use of risk quotient calculations to summarize the cumulative effects of different OHC classes and mercury for which critical body burdens can be estimated for wildlife across the Arctic. As our ultimate goal is to better predict or estimate the effects of OHCs and mercury in Arctic wildlife at the individual, population and ecosystem level, there remain numerous knowledge gaps on the biological effects of exposure in Arctic biota. These knowledge gaps include the establishment of concentration thresholds for individual compounds as well as for realistic cocktail mixtures that in fact indicate biologically relevant, and not statistically determined, health effects for specific species and subpopulations. Finally, we provide future perspectives on understanding Arctic wildlife health using new in vivo, in vitro, and in silico techniques, and provide case studies on multiple stressors to show that future assessments would benefit from significant efforts to integrate human health, wildlife ecology and retrospective and forecasting aspects into assessing the biological effects of OHC and mercury exposure in Arctic wildlife and fish.

Science of the Total Environment↗

USGS2019

Moving at the speed of flight: Dabbling duck-movement rates and the relationship with electronic tracking interval

Context. Effective wildlife management requires information on habitat and resource needs, which can be estimated with movement information and modelling energetics. One necessary component of avian models is flight speeds at multiple temporal scales. Technology has limited the ability to accurately assess flight speeds, leading to estimates of questionable accuracy, many of which have not been updated in almost a century. Aims. We aimed to update flight speeds of ducks, and differentiate between migratory and non-migratory flight speeds, a detail that was unclear in previous estimates. We also analysed the difference in speeds of migratory and non-migratory flights, and quantified how data collected at different temporal intervals affected estimates of flight speed. Methods. We tracked six California dabbling duck species with high spatio-temporal resolution GPS–GSM transmitters, calculated speeds of different flight types, and modelled how estimates varied by flight and data interval (30 min to 6 h). Key results. Median migratory speeds were faster (but non-significant) for the larger mallard (Anas platyrhynchos; 82.5 km h–1), northern pintail (Anas acuta; 79.0 km h–1) and gadwall (Mareca strepera; 70.6 km h–1), than the smaller-bodied northern shoveler (Spatula clypeata; 65.7 km h–1), cinnamon teal (Spatula cyanoptera; 63.5 km h–1) and American wigeon (Mareca Americana; 52 km h–1). Migratory flights were faster than non-migratory flights for all species and speeds were consistently slower with an increasing data interval. Implications. The need to balance time and energy requirements may drive different speeds for migratory and non-migratory flights. Lower speeds at longer intervals are likely to be due to a greater proportion of ‘loafing’ time included in flighted segments, demonstrating that data acquired at different intervals provide a means to evaluate and estimate behaviours that influence speed estimation. Shorter-interval data should be the most accurate, but longer-interval data may be easier to collect over lengthier timeframes, so it may be expedient to trade-off a degree of accuracy in broad-scale studies for the larger dataset. Our updated flight speeds for dabbling duck species can be used to parameterise and validate energetics models, guide management decisions regarding optimal habitat distribution, and, ultimately, improve conservation management of wetlands for waterfowl.

Wildlife Research↗