High population prevalence of neonicotinoids in sharp-tailed grouse and greater prairie-chickens across an agricultural gradient during spring and fall

Neonicotinoids have been detected in many species of wild birds; however, few studies have quantified population-level exposure. We examined population-level exposure to 7 neonicotinoids in 2 species that use agricultural areas, sharp-tailed grouse (Tympanuchus phasianellus) and greater prairie-chickens (T. cupido). We sampled fecal pellets at leks in spring and collected livers from hunter-harvested birds in fall along an agricultural gradient throughout their respective ranges in Minnesota, USA. Most sharp-tailed grouse (93 %) and prairie-chicken (80 %) fecal pellets and livers (90 % and 76 %, respectively) had detectable concentrations of ≥1 neonicotinoid, with imidacloprid (IMI) and clothianidin (CLO) most commonly detected. Spring detections of IMI in both species increased with the proportion of a 2-km buffer in cultivation surrounding sampling locations and varied by year. A similar relationship with cultivation was not supported for CLO, which may reflect differences in the availability of seed types treated with IMI and CLO on the soil surface after planting. However, we also detected IMI and CLO from birds sampled in areas of low cultivation. Sharp-tailed grouse and prairie-chickens may select crop fields preferentially to forage, and thus have a higher risk of exposure than would be expected based only on the amount of cultivation. Year was important in models of IMI and CLO in both species and seasons, which likely reflects differences in planting and in the availability of natural foods among years. In contrast, the proportion of surrounding area in cultivation was not supported in models of fall neonicotinoid detections. Fewer crops are planted in the fall in Minnesota and grouse may be exposed through routes other than treated seeds. High detections, even in areas with little cultivation and during seasons with little planting, likely reflect prairie grouse selection of cultivated fields for food, but may also indicate that exposure risk extends beyond sites of application.

Wildlife consumption of neonicotinoid-treated seeds at simulated seed spills

The most likely route of exposure to high concentrations of neonicotinoids capable of producing lethal or sublethal effects in birds and mammals is consumption of treated seeds. We placed trail cameras at simulated seed spills to document wildlife consuming treated seeds during the spring planting season. We simulated 4 types of spills, corn treated with 2 concentrations of clothiandin (0.50 or 0.25 mg/seed), corn treated with thiamethoxam (0.25 mg/seed), and soybean treated with imidacloprid (0.15 mg/seed). We documented 16 species of birds and 14 species of mammals eating neonicotinoid-treated seeds at spills. Of these, we quantified consumption of treated seeds by 12 species of birds and 13 species of mammals. Birds and mammals did not consume enough seeds to exceed published LD50s in related taxa, but most species did consume enough seeds to reach or exceed thresholds for sublethal effects based on currently available studies. Birds and mammals did not increase the amount of seeds consumed over time, as would be expected if responsive to the concentration of neonicotinoids on seeds, but more birds and mammals consumed seeds over time, as a proportion of the number at spills each day. More birds also consumed seeds after a soaking rain event, which likely reduced the amount of treatment on the seeds. Importantly, wildlife are consuming seeds while neonicotinoids are still concentrated on seeds. Our findings indicate that previously held assumptions about the safety of neonicotinoid seed treatments for vertebrate wildlife need to be revisited.

Sublethal and Lethal Methods to Detect Recent Imidacloprid Exposure in Birds with Application to Field Studies

We used domestic chickens (Gallus gallus domesticus) as a model for granivorous birds to identify methods to detect recent imidacloprid exposure in wild birds. We conducted dosing experiments of 1, 5, 10, and 20% of a reported median lethal dose for domestic chickens using repeated daily exposures over 7 d, at dosages equating to 1.04, 5.2, 10.4, and 20.8 mg/kg/d. We examined the parent compound and metabolites in serial collections of feces and blood during exposures and for 15 d after exposures. We also collected liver, kidney, brain, muscle, and spleen at the experiment end. Mean concentrations of parent compound at 15 d postexposure were highest in the feces and brain, followed by the liver, muscle, spleen, and kidney; but mean concentrations of metabolites 5-OH-imidacloprid and imidacloprid-olefin were highest in feces; then liver, spleen, muscle, and kidney; and then brain. Imidacloprid was rapidly cleared from blood, with only one individual in any dose group having detectable concentrations after 48 h. In contrast, fecal pellets had the highest frequency of imidacloprid detection after 15 d. Concentrations of metabolites were higher than those of the parent compound at all sampling times examined but provided no information about time since exposure. Feces may provide a reliable nonlethal method for detection of recent imidacloprid exposure in wild birds. Additional work is needed to disentangle exposure dose concentration and time since exposure in field-collected samples. Environ Toxicol Chem 2020;39:1355-1366. © 2020 SETAC.

Evaluation of neurobehavioral abnormalities and immunotoxicity in response to oral imidacloprid exposure in domestic chickens (Gallus gallus domesticus)

Domestic chickens (Gallus gallus domesticus) were exposed to imidacloprid by gavage once daily for 7 consecutive days at 0, 0.03, 0.34, 3.42, 10.25, and 15.5 mg/kg/day (n = 20 per group; 5 6-week-old males, 5 6-week-old females, 5 9-week-old males, and 5 9-week-old females). The severity and duration of neurobehavioral abnormalities were recorded. Components of the innate and adaptive immune system were assessed with 7 standard functional assays. Temporary neurobehavioral abnormalities were observed in a dose-dependent manner, including muscle tremors, ataxia, and depressed mentation. Based upon mean clinical severity scores, the no observed adverse effect level (NOAEL) was 3.42 mg/kg/day, and the lowest observed adverse effect level (LOAEL) was 10.25 mg/kg/day. The effective dose value for the presence of any neurobehavioral abnormalities in 50% of the test group (ED₅₀) was 4.62 ± 0.98 mg/kg/day. The ED₅₀ for an adjusted score that included both severity and duration of neurobehavioral abnormalities was 11.24 ± 9.33 mg/kg/day. These ED₅₀ values are equivalent to a 1 kg bird ingesting 29 or 70 imidacloprid treated soybean seeds respectively. Immunotoxicity was not documented, possible causes include the assays were insensitive, relevant immune functions were not examined, or imidacloprid is not immunotoxic at this dosing schedule in this species. Neurobehavioral abnormalities were a more sensitive indicator of the sublethal effects of imidacloprid than immunotoxicity.

Multi-scale availability of neonicotinoid-treated seed for wildlife in an agricultural landscape during spring planting

Neonicotinoid pesticides are applied to seeds and are known to cause lethal and sub-lethal effects in birds and mammals. Neonicotinoid-treated seeds could be available to wildlife through spillage or exposed seeds near or at the soil surface due to incomplete or shallow drilling. We quantified seed spills that may occur during loading or refilling the hopper at a landscape-scale using road-based surveys. We also quantified undrilled seeds in 1-m2 frames on the soil in the center and corner of fields to obtain estimates at the field scale. We broadcast seeds on the soil surface of a tilled field and left them for 0, 1, 2, 4, 8, 16, and 30 days to quantify the decrease of neonicotinoids under field conditions. Lastly, we documented wildlife at neonicotinoid-treated seed spills with trail cameras. We estimated the number of spills during planting to be 3496 (95% CI: 1855-5138) and 2609 (95% CI: 862-4357) for corn, 11,009 (95% CI: 6950-15,067) and 21,105 (95% CI: 6162-36,048) for soybean, and 830 (95% CI: 160-1500) and 791 (95% CI: 0-1781) for wheat in 2016 and 2017, respectively. Exposed seeds were present at the soil surface in 35% of 71 fields. The probability that seeds were present on the soil surface was higher for soybeans (18.8 and 49.4% in the center and corners, respectively) than for corn (1.6 and 2.7%, respectively), and seed densities were also higher (1.04 vs 0.07 seeds/m2, respectively). Neonicotinoids decreased rapidly on seeds on the soil surface but persisted as long as 30 days. Over a dozen species of birds and mammals consumed seeds at simulated spills, with an average time for birds to find spills of 1.3 ± 1.5 days and an average time to consumption of 4.1 ± 3.4 days. Seeds are abundant on the soil surface for wildlife to consume during the spring planting season and should be considered in pesticide risk assessments.

A landscape genetic analysis of swamp rabbits (Sylvilagus aquaticus) suggests forest canopy cover enhances gene flow in an agricultural matrix

Habitat loss and fragmentation pose a continued and immediate threat to wildlife and create a persistent need for ecological information at the landscape scale to guide conservation efforts. Landscape features influence population connectivity for many species and genetic analyses can be employed to determine which of these features are most important. Because population connectivity through dispersal is important to the persistence of swamp rabbits (Sylvilagus aquaticus (Bachman, 1837)) at the northern edge of their range, we used a landscape genetic approach to relate gene flow to landscape features that may impact dispersal success. We tested resistance values for attributes of land cover, watercourse corridors, canopy cover, and roads and used causal modeling and redundancy analysis to relate these representations of landscapes to genetic distance for swamp rabbits in southern Illinois, USA. Models that included canopy cover had the strongest correlations with genetic distance and were supported by our methods whereas other models were not. We concluded that high tree canopy cover enhances gene flow and landscape connectivity for swamp rabbits in southern Illinois. Our study provides important empirical evidence that landscape variables may impact the habitat connectivity of swamp rabbits. Preserving dispersal routes for swamp rabbits should focus on improving canopy cover, in both bottomland and upland, to connect suitable habitat.

Spatio-temporal variation in prevalence and intensity of trematodes responsible for waterfowl die-offs in faucet snail-infested waterbodies of Minnesota, USA

Several non-native trematodes hosted by the invasive Eurasian faucet snail, Bithynia tentaculata, have been causing die-offs of waterfowl in the Midwestern United States and Canada for several decades. Because of the potential implications of these die-offs on waterfowl in non-native settings, it is necessary to better understand the trematodes that cause the die-offs. Here, we studied the spatio-temporal dynamics of two trematodes, Cyathocotyle bushiensis and Sphaeridiotrema spp., known to infect waterfowl in northern Minnesota, USA, via their intermediate host, the faucet snail (Bithynia tentaculata). We studied prevalence (% of snails infected within a sample) and intensity (mean number of parasites per infected snail within a sample) of faucet snail infection with these two trematodes in small lakes, large lakes, ponds, and rivers in northern Minnesota in the spring, summer, and fall of 2011-2013. We tested whether parasite prevalence and infection intensity could be explained spatially (as a function of the abundance of faucet snails, average snail size, water depth, and proximity to known waterfowl groups) and temporally (across years and seasons) using generalized estimating equation models. The spatial and temporal patterns we observed varied within and among waterbodies. For both parasite species, parasite prevalence and intensity of infection were consistently higher in samples with larger snails and in deeper portions of the waterbodies. In Lake Winnibigoshish, prevalence was lower farther from the large waterfowl groups we observed, but the abundance of snails in a sample had no effect on prevalence or intensity of infection. Our findings help improve understanding of this multi-species system, but also illustrate the complexity of modeling the spatial and temporal dynamics of infections in waterbodies that are so variable in size, shape, waterfowl use, and function.

Thinking like a duck: fall lake use and movement patterns of juvenile ring-necked ducks before migration

The post-fledging period is one of the least studied portions of the annual cycle in waterfowl. Yet, recruitment into the breeding population requires that young birds have sufficient resources to survive this period. We used radio-telemetry and generalized estimating equations to examine support for four hypotheses regarding the drivers of landscape scale habitat use and movements made by juvenile ring-necked ducks between the pre-fledging period and departure for migration. Our response variables included the probability of movement, distances moved, and use of different lake types: brood-rearing lakes, staging lakes, and lakes with low potential for disturbance. Birds increased their use of staging areas and lakes with low potential for disturbance (i.e., without houses or boat accesses, >100 m from roads, or big lakes with areas where birds could sit undisturbed) throughout the fall, but these changes began before the start of the hunting season and their trajectory was not changed by the onset of hunting. Males and females moved similar distances and had similar probabilities of movements each week. However, females were more likely than males to use brood-rearing lakes later in the fall. Our findings suggest juvenile ring-necked ducks require different lake types throughout the fall, and managing solely for breeding habitat will be insufficient for meeting needs during the post-fledging period. Maintaining areas with low potential for disturbance and areas suitable for staging will ensure that ring-necked ducks have access to habitat throughout the fall.

Body size and sexual size dimorphism in primates: influence of climate and net primary productivity

Understanding the evolution of body size and sexual size dimorphism has been a longstanding goal in evolutionary biology. Previous work has shown that environmental stress can constrain male-biased sexual size dimorphism at the population level, but we know little about how this might translate to geographical patterns of body size and sexual size dimorphism at the species level. Environmental constraints due to a highly seasonal, resource-poor and/or variable environment have often been cited to explain the unusual lack of sexual size dimorphism among Madagascar's diverse and numerous primate taxa; however, empirical tests of this hypothesis are lacking. Using a phylogenetic approach and a geographical information system platform, we explored the role of seasonality, interannual variability and annual measures of temperature and rainfall, and net primary productivity on patterns of body size and sexual size dimorphism across 130 species of primates. Phylogenetically controlled comparisons showed no support for a role of environmental constraints in moderating sexual size dimorphism at the interspecific level, despite significant associations of environmental variables with body mass. Results suggest that the focus of discussions that have dominated in the last two decades regarding the role of environmental constraints in driving patterns of monomorphism of Madagascar's lemurs should be reconsidered; however, the conundrum remains.

Developing nursing knowledge: practice issues raised from four philosophical perspectives

Analysis and comparison of emerging perspectives in nursing on some of the key issues of practice theory can create an enhanced vision of the discipline. Four philosophy-of-science perspectives--realism, relativism, interpretivism, and humanism--are catalysts for fruitful insights about practice. However, together they generate more questions than they answer, both from each perspective and from the intersection of the assumptions of the four philosophies about the nature of knowledge. The nature of knowledge for practice emerges from examining how the philosophical basis and the derived practice theories address such issues as the phenomena of the discipline, environment, teleology, and nursing theoretical frameworks. This is the time for good debate and collaborative knowledge-building among scholars of various persuasions within a milieu of ethos, pathos, and logic.