Geology topics

Todd W. Arnold

Publications and source records attributed to Todd W. Arnold.

15 recordsLinked to original sources

USGS2024

Sampling for disease surveillance: Assessing effects on blue-winged teal survival and recovery

Outbreaks of highly pathogenic avian influenza virus in wild animals highlight the need for disease surveillance in wild birds to improve our understanding of their role as reservoirs and dispersers, and potential threats to domestic poultry and wild bird populations. Surveillance for avian influenza varies in its approach, objectives, and coordination with other monitoring efforts. For waterfowl, a common host to avian influenza viruses, banding represents a concerted effort of capturing and marking thousands of individuals annually to estimate survival and harvest rates, but users of these data have generally taken a conservative approach to remove any banded birds from analyses that had a sample taken for disease surveillance during capture. We tested for differences in survival and encounter probabilities of blue-winged teal ( Spatula discors ) marked ( n = 21,702 teal) and sampled for disease surveillance ( n = 4,216) during the nonbreeding season in Louisiana, USA, from 2016 to 2023. Although we found no consistent effect of collecting biological samples on survival probability, including an additional test showing no detectable effects of sampling for disease surveillance with oropharyngeal and cloacal swabs versus sampling with swabs and a syringe-drawn blood sample, wide 95% credible intervals on the posterior survival estimates (mean 0.36 difference between upper and lower values across all year-sex-sampling groups; 0.44 for sampling type groups) indicated low statistical power to detect an effect. Seber recovery probability during the first interval following sampling was lower among birds sampled using swabs only, but we assume this stems from low sample sizes rather than an effect of collecting biological samples. Because recovery probabilities can vary as a function of individual covariates, we also examined direct recovery probabilities and observed no meaningful effect of disease surveillance sampling type but strong effects of capture date, suggesting the effect on Seber recovery probability may have been due to heterogeneity in exposure to natural and harvest mortality risks. Although we suggest that aligning disease surveillance sample collection efforts with landscape-scale waterfowl banding efforts may have little effect on observed demographic rates, additional studies with larger sample sizes are likely needed to provide the statistical power necessary to formally conclude no effect of biological sampling on survival probabilities.

Louisiana↗

USGS2023

Evaluation of fall-seeded cover crops for grassland nesting waterfowl in eastern South Dakota

The Prairie Pothole Region (PPR) is the primary breeding ground for many species of North American waterfowl. The PPR was historically dominated by mixed and tallgrass prairies interspersed with wetlands, but >70% of the native grassland area has been lost due to widespread conversion to croplands. Cover cropping is a reemerging farming technique that may provide suitable nesting cover for grassland nesting waterfowl in active croplands, but waterfowl nest survival in fall cover-cropped fields has not been evaluated. We studied use (nest abundance and density) and nest survival of breeding waterfowl in fall-seeded cover crops and perennial cover during 2018 and 2019. We searched 2,094 ha of cover crops and 1,604 ha of perennial cover and found 123 and 304 duck nests, respectively, in each cover type. Estimated nest success (34-day interval) was 3.7% and 16.6% in cover crops during 2018 and 2019, respectively, versus 22.1% in 2018 and 24.9% in 2019 in perennial cover, with increased success of cover-crop fields in 2019 resulting from precipitation that prevented most fields from being planted to row crops. In a model that included effects of planting, daily nest survival in perennial cover was 0.944 (SD = 0.026) in 2018 and 0.960 (SD = 0.019) in 2019. Estimated daily nest survival was 0.912 (SD = 0.040) in 2018 and 0.960 (SD = 0.019) in 2019 during intervals when planting did not occur, but was only 0.417 (SD = 0.124) in 2018 and 0.612 (SD = 0.117) in 2019 on the day that planting occurred. Estimated nest densities in 2018 and 2019, adjusted for nests that failed prior to discovery, were 5.1 (SE = 1.1) and 11.0 (SE = 3.1) nests 100-ha −1 in perennial cover, but only 2.1 (SE = 0.8) and 2.6 (SE = 0.7) in cover crops, respectively. Based on observed nest initiation and planting dates, about 70% of duck nests in cover crops would experience planting events in a typical growing season. Our results suggest that under current management techniques, fall-seeded cover crops offer poor nesting habitat for waterfowl; however, the important benefits cover crops provide to soil health, water quality, and other ecosystem services remain.

South Dakota↗

USGS2020

Modeling water quality in watersheds: From here to the next generation

In this synthesis, we assess present research and anticipate future development needs in modeling water quality in watersheds. We first discuss areas of potential improvement in the representation of freshwater systems pertaining to water quality, including representation of environmental interfaces, in‐stream water quality and process interactions, soil health and land management, and (peri‐)urban areas. In addition, we provide insights into the contemporary challenges in the practices of watershed water quality modeling, including quality control of monitoring data, model parameterization and calibration, uncertainty management, scale mismatches, and provisioning of modeling tools. Finally, we make three recommendations to provide a path forward for improving watershed water quality modeling science, infrastructure, and practices. These include building stronger collaborations between experimentalists and modelers, bridging gaps between modelers and stakeholders, and cultivating and applying procedural knowledge to better govern and support water quality modeling processes within organizations.

Water Resources Research↗

USGS2020

Habitat use by tiger prey in Thailand’s Western Forest Complex: What will it take to fill a half-full tiger landscape?

Tiger populations are declining globally, and depletion of major ungulate prey is an important contributing factor. To better understand factors affecting prey distribution in Thailand’s Western Forest Complex (WEFCOM), we conducted sign surveys for gaur (Bos gaurus ), banteng ( Bos javanicus ), and sambar ( Rusa unicolor ) along 3517 1-km transects and used occupancy models to identify important covariates associated with habitat use by each species. Habitat use by both gaur and sambar was lowest in areas closest to human settlements, although sambar preferred lower slopes near streams whereas gaur preferred steeper slopes at higher elevations. Banteng were found in only one of 17 protected areas (Huai Kha Khaeng [HKK] Wildlife Sanctuary), where they used low elevations and low slopes. We used these modeled relationships to predict occurrence of gaur, sambar, and banteng across each square km of the 19,000 km 2 WEFCOM landscape, using > 60 % occupancy probability to define suitable habitat use for each species. Based on this criterion, gaur and sambar occupied 28 and 50 % of suitable habitat in WEFCOM, and banteng occupied 57 % of suitable habitat in HKK. We used our models to assess the effectiveness of two hypothetical conservation initiatives. First, we modeled the impact of decreasing human activities around nine villages in the core of WEFCOM, which increased predicted suitable habitat in WEFCOM to 68 and 75 % for guar and sambar. We also modeled the extent of potential banteng habitat that still remains in the other 16 protected areas. This could result in a 4-fold increase in banteng suitable habitat in WEFCOM. This is the first study to use occupancy surveys to determine where large prey species can be restored to support management to increase the distribution of tigers, and potentially fill a half-full tiger landscape.

Journal for Nature Conservation↗

USGS2019

Impact of prey occupancy and other ecological and anthropogenic factors on Tiger distribution in Thailand’s Western Forest Complex

Despite conservation efforts, large mammals such as tigers (Panthera tigris) and their main prey, gaur (Bos gaurus), banteng (Bos javanicus), and sambar (Rusa unicolor), are highly threatened and declining across their entire range. The only large viable source population of tigers in mainland Southeast Asia occurs in Thailand's Western Forest Complex (WEFCOM), an approximately 19,000 km 2 landscape of 17 contiguous protected areas. We used an occupancy modeling framework, which accounts for imperfect detection, to identify the factors that affect tiger distribution at the approximate scale of a female tiger's home range, 64 km 2 , and site use at a scale of 1-km 2 . At the larger scale, we estimated the proportion of sites at WEFCOM that were occupied by tigers; at the finer scale, we identified the key variables that influence site-use and developed a predictive distribution map. At both scales, we examined key anthropogenic and ecological factors that help explain tiger distribution and habitat use, including probabilities of gaur, banteng, and sambar occurrence from a companion study. Occupancy estimated at the 64-km 2 scale was primarily influenced by the combined presence of all three large prey species, and 37% or 5,858 km 2 of the landscape was predicted to be occupied by tigers. In contrast, site use estimated at the scale of 1 km 2 was most strongly influenced by the presence of sambar. By modeling occupancy while accounting for imperfect probability of detection, we established reliable benchmark data on the distribution of tigers in WEFCOM. This study also identified factors that limit tiger distributions; which managers can then target to expand tiger distribution and guide recovery elsewhere in Southeast Asia.

Ecology and Evolution↗

USGS2018

Nesting ecology of a naturalized population of Mallards Anas platyrhynchos in New Zealand

Investigating the reproductive ecology of naturalized species provides insights into the role of the source population's characteristics vs. post‐release adaptation that influence the success of introduction programmes. Introduced and naturalized Mallards Anas platyrhynchos are widely established in New Zealand (NZ), but little is known regarding their reproductive ecology. We evaluated the nesting ecology of female Mallards at two study sites in NZ (Southland and Waikato) in 2014–15. We radiotagged 241 pre‐breeding females with abdominal‐implant transmitters and measured breeding incidence, nesting chronology and re‐nesting propensity. We monitored 271 nests to evaluate nest survival, clutch and egg size, egg hatchability and partial clutch depredation. Breeding incidence averaged (mean ± se) 0.91 ± 0.03, clutch size averaged 9.9 ± 0.1 eggs, 94 ± 2% of eggs hatched in successful nests, partial depredation affected 6 ± 1% of eggs in clutches that were not fully destroyed by predators, and re‐nesting propensity following failure of nests or broods was 0.50 ± 0.003. Nesting season (first nest initiated to last nest hatched) lasted 4.5 months and mean initiation date of first detected nest attempts was 28 August ± 3.3 days. Smaller females were less likely to nest, but older, larger or better condition females nested earlier, re‐nested more often and laid larger clutches than did younger, smaller or poorer condition females. Younger females in Southland had higher nest survival; cumulative nest survival ranged from 0.25 ± 0.007 for adult females in Waikato to 0.50 ± 0.007 for yearling females in Southland. Compared with Mallards in their native range, the nesting season in NZ was longer, clutches and eggs were larger, and nest survival was generally greater. Different predators and climate, introgression with native heterospecifics and/or the sedentary nature of Mallards in NZ may have contributed to these differences.

Ibis↗

USGS2017

Effects of surgically implanted transmitters on reproduction and survival in mallards

Abdominally implanted radiotransmitters have been widely used in studies of waterbird ecology; however, the longer handling times and invasiveness of surgical implantation raise important concerns about animal welfare and potential effects on data quality. Although it is difficult to assess effects of handling and marking wild animals by comparing them with unmarked controls, insights can often be obtained by evaluating variation in handling or marking techniques. Here, we used data from 243 female mallards ( Anas platyrhynchos ) and mallard–grey duck hybrids ( A. platyrhynchos × A. superciliosa ) equipped with fully encapsulated abdominally implanted radiotransmitters from 2 study sites in New Zealand during 2014–2015 to assess potential marking effects. We evaluated survival, dispersal, and reproductive effort (e.g., breeding propensity, nest initiation date, clutch size) in response to 3 different attributes of handling duration and procedures: 1) processing time, including presurgery banding, measurements, and blood sampling of unanaesthetized birds; 2) surgery time from initiation to cessation of anesthetic; and 3) total holding time from first capture until release. We found no evidence that female survival, dispersal probability, or reproductive effort were negatively affected by holding, processing, or surgery time and concluded that we collected reliable data without compromising animal welfare. Our results support previous research that techniques using fully encapsulated abdominal-implant radiotransmitters are suitable to enable researchers to obtain reliable estimates of reproductive performance and survival.

Wildlife Society Bulletin↗

USGS2017

Temporal variation in survival and recovery rates of lesser scaup: A response

We recently analyzed long-term (1951–2011) continental band-recovery data from lesser scaup ( Aythya affinis ) and demonstrated that harvest rates declined through time, but annual survival rates exhibited no such trends; moreover, annual harvest and survival rates were uncorrelated for all age-sex classes. We therefore concluded that declining fecundity was most likely responsible for recent population declines, rather than changes in harvest or survival. Lindberg et al. ( 2017 ) critiqued our conclusions, arguing that we did little more than fail to reject a null hypothesis of compensatory mortality, postulated ecologically unrealistic changes in fecundity, and failed to give sufficient consideration to additive harvest mortality. Herein, we re-summarize our original evidence indicating that harvest has been compensatory, or at most weakly additive, and demonstrate that our analysis had sufficient power to detect strongly additive mortality if it occurred. We further demonstrate that our conclusions were not confounded by population size, band loss, or individual heterogeneity, as suggested by Lindberg et al. ( 2017 ), and we provide additional support for our conjecture that low fecundity played a major role in declining scaup populations during 1983–2006. We therefore reiterate our original management recommendations: given low harvest rates and lack of demonstrable effect on scaup survival, harvest regulations could return to more liberal frameworks, and waterfowl biologists should work together to continue banding lesser scaup and use these data to explore alternative hypotheses to identify the true ecological causes of population change, given that it is unlikely to be excessive harvest.

Journal of Wildlife Management↗

USGS2016

Detection, prevalence, and transmission of avian hematozoa in waterfowl at the Arctic/sub-Arctic interface: co-infections, viral interactions, and sources of variation.

Background: The epidemiology of avian hematozoa at high latitudes is still not well understood, particularly in sub-Arctic and Arctic habitats, where information is limited regarding seasonality and range of transmission, co-infection dynamics with parasitic and viral agents, and possible fitness consequences of infection. Such information is important as climate warming may lead to northward expansion of hematozoa with unknown consequences to northern-breeding avian taxa, particularly populations that may be previously unexposed to blood parasites. Methods: We used molecular methods to screen blood samples and cloacal/oropharyngeal swabs collected from 1347 ducks of five species during May-August 2010, in interior Alaska, for the presence of hematozoa, Influenza A Virus (IAV), and IAV antibodies. Using models to account for imperfect detection of parasites, we estimated seasonal variation in prevalence of three parasite genera (Haemoproteus, Plasmodium, Leucocytozoon) and investigated how co-infection with parasites and viruses were related to the probability of infection. Results: We detected parasites from each hematozoan genus in adult and juvenile ducks of all species sampled. Seasonal patterns in detection and prevalence varied by parasite genus and species, age, and sex of duck hosts. The probabilities of infection for Haemoproteus and Leucocytozoon parasites were strongly positively correlated, but hematozoa infection was not correlated with IAV infection or serostatus. The probability of Haemoproteus infection was negatively related to body condition in juvenile ducks; relationships between Leucocytozoon infection and body condition varied among host species. Conclusions: We present prevalence estimates for Haemoproteus, Leucocytozoon, and Plasmodium infections in waterfowl at the interface of the sub-Arctic and Arctic and provide evidence for local transmission of all three parasite genera. Variation in prevalence and molecular detection of hematozoa parasites in wild ducks is influenced by seasonal timing and a number of host traits. A positive correlation in co-infection of Leucocytozoon and Haemoproteus suggests that infection probability by parasites in one or both genera is enhanced by infection with the other, or that encounter rates of hosts and genus-specific vectors are correlated. Using size-adjusted mass as an index of host condition, we did not find evidence for strong deleterious consequences of hematozoa infection in wild ducks.

Parasites & Vectors↗

USGS2016

Temporal variation in survival and recovery rates of lesser scaup

Management of lesser scaup (Aythya affinis) has been hindered by access to reliable data on population trajectories and vital rates. We conducted a Bayesian analysis of historical (1951–2011) band-recovery data throughout North America to estimate annual survival and recovery rates for juvenile and adult male and female lesser scaup to determine if increasing harvest or declining survival rates have contributed to population changes and to determine if harvest has been primarily additive or compensatory. Annual recovery rates were low, ranging from 1% to 4% for adults and 2% to 10% for juveniles during most years, with trend models indicating that recovery rates have declined through time for all age–sex classes. Annual survival (mid-Aug to mid-Aug) averaged 0.402 (σ ̂ 0.043) for juvenile males, 0.416 (σ ̂ 0.067) for juvenile females, 0.689 (σ ̂ 0.109) for adult males, and 0.602 (σ ̂ 0.115) for adult females, where σ ̂ represents an estimate of annual process variation in each survival rate. Annual survival rates exhibited no evidence of long-term declines or negative correlations with annual recovery rates (i.e., an index of harvest intensity) for any age–sex class, suggesting that declining fecundity was the most likely explanation for population declines during 1975–2005. We conclude that hunting mortality played a minor role in affecting population dynamics of lesser scaup and waterfowl managers could take a less cautious approach in managing harvest, especially if recruiting or maintaining waterfowl hunters are viewed as important management objectives.

Journal of Wildlife Management↗

USGS2015

Evaluation of autonomous recording units for detecting 3 species of secretive marsh birds

Population status and habitat use of yellow rails ( Coturnicops noveboracensis ), Nelson's sparrows ( Ammodramus nelsoni ), and Le Conte's sparrows ( A. leconteii ) are poorly known, so standardized surveys of these species are needed to inform conservation planning and management. A protocol for monitoring secretive marsh birds exists; however, these species regularly call at night and may be missed during early morning surveys. We tested the effectiveness of autonomous recording units (hereafter, recording units) to survey these species by analyzing recorded vocalizations using bioacoustics software. We deployed 22 recording units at 54 sites in northern Minnesota and eastern North Dakota, USA, and conducted traditional broadcast surveys during May–June, 2010 and 2011. We compared detection probabilities between recording units and standard monitoring protocols using robust-design occupancy models. On average, recording units detected 0.59 (SE = 0.11) fewer Le Conte's sparrows, 0.76 (SE = 0.15) fewer Nelson's sparrows, and 1.01 (SE = 0.14) fewer yellow rails per survey than were detected using the standard protocol. Detection probabilities using the standard protocol averaged 0.95 (yellow rail; 95% CI = 0.86–0.98), 0.93 (Le Conte's sparrow; 95% CI = 0.78–0.98), and 0.89 (Nelson's sparrow; 95% CI = 0.56–0.98), but averaged 0.71 (yellow rail; 95% CI = 0.56–0.83), 0.61 (Le Conte's sparrow; 95% CI = 0.42–0.78), and 0.51 (Nelson's sparrow; 95% CI = 0.19–0.82) using recording units. Reduced detection by recording units was likely due to the ability of human listeners to identify birds calling at greater distances. Recording units may be effective for surveying nocturnal secretive marsh birds if investigators correct for differential detectability. Reduced detectability may be outweighed by the increased spatial and temporal coverage feasible with recording units.

Minnesota, North Dakota↗

USGS2014

Field‐readable alphanumeric flags are valuable markers for shorebirds: use of double‐marking to identify cases of misidentification

Implicit assumptions for most mark-recapture studies are that individuals do not lose their markers and all observed markers are correctly recorded. If these assumptions are violated, e.g., due to loss or extreme wear of markers, estimates of population size and vital rates will be biased. Double-marking experiments have been widely used to estimate rates of marker loss and adjust for associated bias, and we extended this approach to estimate rates of recording errors. We double-marked 309 Piping Plovers ( Charadrius melodus ) with unique combinations of color bands and alphanumeric flags and used multi-state mark recapture models to estimate the frequency with which plovers were misidentified. Observers were twice as likely to read and report an invalid color-band combination (2.4% of the time) as an invalid alphanumeric code (1.0%). Observers failed to read matching band combinations or alphanumeric flag codes 4.5% of the time. Unlike previous band resighting studies, use of two resightable markers allowed us to identify when resighting errors resulted in reports of combinations or codes that were valid, but still incorrect; our results suggest this may be a largely unappreciated problem in mark-resight studies. Field-readable alphanumeric flags offer a promising auxiliary marker for identifying and potentially adjusting for false-positive resighting errors that may otherwise bias demographic estimates.

North Dakota, South Dakota↗

USGS2014

A multiscale assessment of tree avoidance by prairie birds

In North America, grassland bird abundances have declined, likely as a result of loss and degradation of prairie habitat. Given the expense and limited opportunity to procure new grasslands, managers are increasingly focusing on ways to improve existing habitat for grassland birds, using techniques such as tree removal. To examine the potential for tree removal to benefit grassland birds, we conducted 446 point counts on 35 grassland habitat patches in the highly fragmented landscape of west-central Minnesota during 2009–2011. We modeled density of four grassland bird species in relation to habitat composition at multiple scales, focusing on covariates that described grass, woody vegetation (trees and large shrubs), or combinations of grass and woody vegetation. The best-supported models for all four grassland bird species incorporated variables measured at multiple scales, including local features such as grass height, litter depth, and local tree abundance, as well as landscape-level measures of grass and tree cover. Savannah Sparrows ( Passerculus sandwichensis ), Sedge Wrens ( Cistothorus platensis ), and Bobolinks ( Dolichonyx oryzivorus ) responded consistently and negatively to woody vegetation, but response to litter depth, grass height, and grassland extent were mixed among species. Our results suggest that reducing shrub and tree cover is more likely to increase the density of grassland birds than are attempts to improve grass quality or quantity. In particular, tree removal is more likely to increase density of Savannah Sparrows and Sedge Wrens than any reasonable changes in grass quality or quantity. Yet tree removal may not result in increased abundance of grassland birds if habitat composition is not considered at multiple scales. Managers will need to either manage at large scales (80–300 ha) or focus their efforts on removing trees in landscapes that contain some grasslands but few nearby wooded areas.

Minnesota↗

USGS2014

Using sightability-adjusted brood-pair ratios to estimate waterfowl productivity

Historically, biologists used brood-pair ratios (BPRs) as an index to waterfowl productivity to help guide management decisions and evaluate conservation practices. However, BPRs are biased by imperfect detection probabilities, especially for broods. We conducted roadside surveys for breeding waterfowl pairs on 7–8 study sites in the springs of 2006–2008 in northeastern North Dakota, USA. Later each year, we conducted replicate counts of broods on the same wetlands and used mark–recapture methods to estimate sightability-adjusted BPRs (SA-BPRs). Traditional roadside brood surveys detected only 30–45% of the available broods, depending on species. We explored the potential for using SA-BPRs to measure hen success (i.e., the probability a female hatches ≥1 egg across all nesting attempts) for mallards (Anas platyrhynchos) and other upland-nesting dabbling ducks (Anas spp.). We found that SA-BPRs explained 40% of the variation in hen success over 5 species of dabbling ducks, and we were able to detect an effect of predator reduction on hen success in combined dabblers, but not in mallards alone. However, we found no relationship between SA-BPRs and mallard fledging rates (hen success × initial brood size × duckling survival). Our results suggest that SA-BPRs can provide a cost-effective alternative to traditional measures of productivity such as nesting success, but not to measures of duckling survival. Nevertheless, SA-BPRs may be useful in areas where traditional measures of waterfowl productivity are logistically or financially challenging.

Wildlife Society Bulletin↗

USGS2005

Incubation length of dabbling ducks

We collected unincubated eggs from wild Mallard ( Anas platyrhynchos ), Gadwall ( A. strepera ), Blue-winged Teal ( A. discors ), and Northern Shoveler ( A. clypeata ) nests and artificially incubated them at 37.5°C. Average incubation lengths of Mallard, Gadwall, and Northern Shoveler eggs did not differ from their wild-nesting counterparts, but artificially incubated Blue-winged Teal eggs required an additional 1.7 days to hatch, suggesting that wild-nesting teal incubated more effectively. A small sample of Mallard, Gadwall, and Northern Shoveler eggs artificially incubated at 38.3°C hatched 1 day sooner, indicating that incubation temperature affected incubation length. Mean incubation length of Blue-winged Teal declined by 1 day for each 11-day delay in nesting, but we found no such seasonal decline among Mallards, Gadwalls, or Northern Shovelers. There is no obvious explanation for the seasonal reduction in incubation length for Blue-winged Teal eggs incubated in a constant environment, and the phenomenon deserves further study.

Condor↗