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At least 775 records · Page 43Linked to original sources
USGS2014

Occurrence, habitat, and movements of the endangered northern madtom ( Noturus stigmosus ) in the Detroit River, 2003-2011

The northern madtom ( Noturus stigmosus or NOM) is a small catfish, native to North America. It is globally vulnerable and endangered in Canada, Ontario, and Michigan. In 1994 and 1996, it was found in the St. Clair River and in Lake St. Clair, respectively. However, it had not been found downstream in the Detroit River since 1978. We report catches of 304 NOM from 2003 to 2011 and describe their mud and sand habitats in the deep (10 m), dark, Detroit River. We found adult NOM, including 3 ripe males (90–107 mm SL) in head waters of the river near Belle Isle in Michigan waters, and both adult and 4 juvenile NOM (21–30 mm SL) near Peche Island in Ontario waters. From 2009 to 2011, in the river's middle reach, we caught 7 adult NOM for the first time near Fighting Island in Ontario waters, but no NOM in the river's lower reach. Our mark–recapture results showed that within 6 weeks, 2 adult NOM moved east 2.0 km from Michigan waters near Belle Isle across the deep (10 m) Fleming Channel of the Detroit River to Canadian waters near Peche Island. Analysis of annuli from pectoral spines of 7 dead NOM revealed that they live to at least 6 years of age in the Detroit River. This is the first age data that we could find for a NOM population. Our findings extended our knowledge of habitat, reproductive ecology, age, and distribution of NOM in the Detroit River corridor.

Michigan, Ontario↗
USGS2016

Vegetation of semi-stable rangeland dunes of the Navajo Nation, Southwestern USA

Dune destabilization and increased mobility is a worldwide issue causing ecological, economic, and health problems for the inhabitants of areas with extensive dune fields. Dunes cover nearly a third of the Navajo Nation within the Colorado Plateau of southwestern USA. There, higher temperatures and prolonged drought beginning in 1996 have produced significant increases in dune mobility. Vegetation plays an important role in dune stabilization, but there are few studies of the plants of the aeolian surfaces of this region. We examined plant species and their attributes within a moderately vegetated dune field of the Navajo Nation to understand the types and characteristics of plants that stabilize rangeland dunes. These dunes supported a low cover of mixed grass-scrubland with fifty-two perennial and annual species including extensive occurrence of non-native annual Salsola spp. Perennial grass richness and shrub cover were positively associated with increased soil sand composition. Taprooted shrubs were more common on sandier substrates. Most dominant grasses had C4 photosynthesis, suggestive of higher water-use efficiencies and growth advantage in warm arid environments. Plant cover was commonly below the threshold of dune stabilization. Increasing sand movement with continued aridity will select for plants adapted to burial, deflation, and abrasion. The study indicates plants tolerant of increased sand mobility and burial but more investigation is needed to identify the plants adapted to establish and regenerate under these conditions. In addition, the role of Salsola spp. in promoting decline of perennial grasses and shrubs needs clarification.

Arizona, Colorado, New Mexico, Utah↗
USGS2006

Simulation of proposed increases in ground-water withdrawals on the Atlantic City 800-foot sand, New Jersey Coastal Plain

The confined Atlantic City 800-foot sand and the unconfined Kirkwood-Cohansey aquifer system (surficial aquifer) are major sources of water for southeastern New Jersey. Because of recent concerns about streamflow depletion resulting from ground-water withdrawals and the potential ecological effects on stream habitat in the area, the focus on future withdrawals has been shifted away from the surficial aquifer to the confined Atlantic City 800-foot sand until the effects of increased withdrawals from the surficial aquifer can be investigated. A study was conducted to evaluate the effects of seven proposed increases in ground-water withdrawals from the Atlantic City 800-foot sand and the Kirkwood-Cohansey aquifer system on the Atlantic City 800-foot sand. The proposed withdrawals are increases above the 2004 allocated rates (full allocation). The effects of full-allocation ground-water withdrawals and the cumulative effect of withdrawals for each of seven proposed increases in withdrawals were simulated using three previously published ground-water flow models: the New Jersey Coastal Plain Regional Aquifer System Analysis model, the Coastal Plain Optimization model, and a model of the Atlantic City 800-foot sand in Atlantic County, New Jersey. These models were used to simulate changes in water levels, the source supplying the increased ground-water flow, and the effects on saltwater movement towards production wells in Cape May County as a result of the proposed increased withdrawals at proposed or existing wells. The results of the simulations represent the effects of the proposed increase from full-allocation withdrawals to an additional 1,825 Mgal/yr (million gallons per year) from the Atlantic City 800-foot sand and an additional 1,045 Mgal/yr from the deep part of the Kirkwood-Cohansey aquifer system near the updip limit of the Atlantic City 800-foot sand. Most of the simulated decline in water levels in Atlantic County occurred as the result of the proposed increased withdrawals simulated for the New Jersey American Water Company wells. Simulated declines in water levels in Cape May were caused mainly by the simulated increased withdrawals for the Cape May City Desalination Plant wells. The additional water to supply the proposed increases in the scenarios was primarily horizontal flow from the unconfined updip part of the Kirkwood-Cohansey aquifer system, which accounted for 63 percent of the inflow, and flow from the overlying Kirkwood-Cohansey aquifer system into the Atlantic City 800-foot sand, which supplied 27 percent of the additional water. Because the withdrawals were made from the confined aquifer and the deeper part of the unconfined aquifer, the effect on streamflow was substantially less than would have occurred had the withdrawals been made directly from the shallower parts of the unconfined aquifer. The travel times from the 250-mg/L isochlor to production wells in Stone Harbor were longer as a result of all the additional withdrawals. For some scenarios, withdrawals in Atlantic County caused the saltwater to move slightly faster towards the production wells. These effects were offset by the increase in travel time caused by the potential increased withdrawals simulated for the Cape May City desalination wells, which either diverted water towards the desalination wells or increased the travel time towards production wells.

New Jersey↗
USGS2026

Who needs closure? Estimating abundance with a Markovian availability model for geographically open removal sampling

Removal sampling is an important method for estimating abundance, but nearly all removal models assume closure during sampling. Yet, closure may be difficult to assume, evaluate, or enforce in many settings. To address situations where populations are geographically open between each removal sample, we incorporated a Markovian availability process into an N-mixture model framework. This model relates local abundance available for sampling to a superpopulation through recruitment of new individuals to the sampling area. To test the model, we (1) conducted parameter identifiability analysis, (2) fit the model to removal data generated from a random walk movement model, and (3) analyzed a case study of empirical removal data. Parameters were increasingly identifiable as capture probability exceeded 0.25 and removal samples increased from 3 to 6. Abundance estimates were unbiased when parameters were identifiable, except for scenarios that simulated a behavioral response to sampling. For our case study, the model estimated negligible recruitment for benthic-oriented fishes, indicating closure, but we found evidence against closure for juvenile Chinook salmon, a highly mobile species. Our removal model allows researchers to formally test closure assumptions, to estimate the degree of closure, and to estimate abundance without bias when closure is violated.

California↗
USGS2019

Resource concentration mechanisms facilitate foraging success in simulations of a pulsed oligotrophic wetland

Context Movement of prey on hydrologically pulsed, spatially heterogeneous wetlands can result in transient, high prey concentrations, when changes in landscape features such as connectivity between flooded areas alternately facilitate and impede prey movement. Predators track and exploit these concentrations, depleting them as they arise. Objectives We sought to describe how prey pulses of fish rapidly form and persist on wetland landscapes, while enduring constant consumption by wading birds, without being fully depleted. Specifically, we questioned how is the predator–prey relationship mediated by interactions between animal movement and dynamic landscape connectivity? Methods Two models were developed of the predator–prey-landscape system with qualitatively different representations of space, to identify and quantify prey pulsing dynamics that were robust across modeled assumptions. The first included a homogeneous landscape described by simple geometry, and implicit fish movement as wetland volume contracts. The second modeled transverse movement across a heterogeneous landscape, with isolated drying patches. Results Both models produced rapid fish prey concentrations as the wetland dried to shallow water depths. These conditions are critical for making prey available to wading birds. Fish were also rapidly depleted by birds, representing daily caloric intake supporting birds. Model 1 provided average estimates across the modeled domain. Model 2 mapped locations of emerging prey hotspots on the landscape through time. Conclusions Our models tracked predator, prey, and landscape dynamics in parallel, inducing systems dynamics from empirical observations. Explicit inclusion of dynamic wetland hydrologic connectivity, a key landscape mechanism, allowed for a comprehensive picture of links between landscape dynamics and the adapted predator–prey system.

Landscape Ecology↗
USGS2008

Preliminary classification of water areas within the Atchafalaya Basin Floodway System by using landsat imagery

The southern portion of the Atchafalaya Basin Floodway System (ABFS) is a large area (2,571 km 2 ) in south central Louisiana bounded on the east and west sides by a levee system. The ABFS is a sparsely populated area that includes some of the Nation's most significant extents of bottomland hardwoods, swamps, bayous, and backwater lakes, holding a rich abundance and diversity of terrestrial and aquatic species. The seasonal flow of water through the ABFS is critical to maintaining its ecological integrity. Because of strong interdependencies among species, habitat quality, and water flow in the ABFS, there is a need to better define the paths by which water moves at various stages of the hydrocycle. Although river level gages have collected a long historical record of water level variation, very little synoptic information has been available regarding the distribution and character of water at more remote locations in the basin. Most water management plans for the ABFS strive to improve water quality by increasing water flow and circulation from the main stem of the Atchafalaya River into isolated areas. To describe the distribution of land and water on a basin-wide scale, we chose to use Landsat 5 and Landsat 7 imagery to determine the extent of water distribution from 1985 to 2006 and at a variety of river stages. Because the visual signature of river water is high turbidity, we also used Landsat imagery to describe the distribution of turbid water in the ABFS. The ability to track water flow patterns by tracking turbid waters will enhance the characterization of water movement and aid in planning.

Louisiana↗
USGS2020

Predicting multi-species foraging hotspots for marine turtles in the Gulf of Mexico

Quantifying the distribution of animals and identifying underlying characteristics that define suitable habitat are essential for effective conservation of free-ranging species. Prioritizing areas for conservation is important in managing a geographic extent that has a high level of disturbance and limited conservation resources. We examined the potential use of a species distribution model ensemble for multi-species conservation in marine habitats. Using satellite telemetry locations during foraging as input data, and ensemble ecological niche models, we predicted foraging areas for 2 nesting marine turtle species within the Gulf of Mexico (GoM): Kemp’s ridley Lepidochelys kempii (n = 63) and loggerhead Caretta caretta (n = 63). We considered 7 geophysical, biological, and climatic variables and compared contributing factors for each species’ foraging habitat selection. For both species, predicted suitable foraging habitats encompassed large areas along the GoM coast, but only intersected with each other in relatively small areas. Highly parameterized models resulted in overall greater fits, suggesting that multiple factors influence habitat selection by these species. Model validation results were mixed: cross-validation resulted in high prediction accuracy for both species, but an evaluation against independent data resulted in a low omission rate (5%) for Kemp’s ridleys and a high omission rate (72%) for loggerheads. The relatively small intersection of model-predicted foraging areas for these 2 species within the study area may indicate possible niche differentiations. The high omission rate for loggerheads indicates our samples likely underrepresent the population and illustrates the challenges in predicting suitable foraging extents for species that make dynamic movements and have greater individual variability.

Gulf of Mexico↗
USGS2025

Home range, seasonality, and the importance of canopy cover for Texas Tortoises (Gopherus berlandieri)

Texas Tortoises ( Gopherus berlandieri ) are understudied compared to federally protected congeners. Despite important early studies on the basic ecology of G. berlandieri , quantitative identification of habitat associations with specific environmental conditions has been limited. Gopherus berlandieri inhabits Tamaulipan thornscrub across its range, and coastal populations are historically associated with low-relief clay ridges with thick mesquital scrub surrounded by salt prairie grasslands. Our study examined tortoise home range size and association with canopy cover and potential ground moisture at a protected natural area in Cameron County, TX, USA. Twelve tortoises were outfitted with GPS loggers that recorded location once an hour from March 2020 to March 2022. To delineate home ranges, we estimated utilization distributions (UDs) for tortoises as autocorrelated kernel density estimates (AKDEs) at low-use (95%) and core-use (50%) levels for each tortoise. UDs were estimated for the entire study period and during seasons of sustained heat or cold to determine if tortoises used space differently across these seasons over the study period. Applying a use-availability study design, we compared canopy cover and potential mesic ground condition (i.e., precipitation flow accumulation) within each tortoise's UD (“use”) to the area within 1 day's movement around the boundary of the UD (“available”). Tortoise UD sizes were significantly different across seasons for low-use (95%) but not for core-use (50%) AKDE levels. Tortoise UDs had greater canopy cover compared to available-but-unused areas at both AKDE levels. Potential mesic ground condition did not significantly differ between available and used areas. Our study revealed that tortoises vary the size of their home ranges throughout the year, whereas areas of intensive use or occupation tended to remain remarkably stable throughout the year. In seasons of extreme weather (hot or cold), tortoises seem to seek out areas of denser canopy cover that likely serve as thermal refugia. Based on our results, effective habitat identification may best be served by ensuring that canopy cover is at least equivalent to the values reported here to ensure sufficient refugia during extreme seasonal temperatures.

Texas↗
USGS2015

A genetic discontinuity in moose ( Alces alces ) in Alaska corresponds with fenced transportation infrastructure

The strength and arrangement of movement barriers can impact the connectivity among habitat patches. Anthropogenic barriers (e.g. roads) are a source of habitat fragmentation that can disrupt these resource networks and can have an influence on the spatial genetic structure of populations. Using microsatellite data, we evaluated whether observed genetic structure of moose ( Alces alces ) populations were associated with human activities (e.g. roads) in the urban habitat of Anchorage and rural habitat on the Kenai Peninsula, Alaska. We found evidence of a recent genetic subdivision among moose in Anchorage that corresponds to a major highway and associated infrastructure. This subdivision is most likely due to restrictions in gene flow due to alterations to the highway (e.g. moose-resistant fencing with one-way gates) and a significant increase in traffic volume over the past 30 years; genetic subdivision was not detected on the Kenai Peninsula in an area not bisected by a major highway. This study illustrates that anthropogenic barriers can substructure wildlife populations within a few generations and highlights the value of genetic assessments to determine the effects on connectivity among habitat patches in conjunction with behavioral and ecological data. .

Alaska↗
USGS2020

Estimation of vital population rates to assess the relative health of mussel assemblages in the Upper Mississippi River

Native freshwater mussels are a guild of benthic, filter feeding invertebrates that perform important ecological functions in rivers. Because of their long lifespans (30–50 years or longer), mussels are slow to respond to human‐induced alterations. Thus, development of sensitive indicators of mussel population responses to river conditions and management would be beneficial. Compared to marine species, estimation of vital rates (e.g. survival, growth) in freshwater mussels has received little attention. We placed passively integrated transponder tags on 578 mussels of four species ( Amblema plicata , Cyclonaias pustulosa , Obliquaria reflexa , and Pleurobema sintoxia ) in a well‐studied mussel assemblage in a side channel of the upper Mississippi River. Growth and survival of tagged mussels were assessed annually for 4 years across core (high density) and peripheral (low density) areas of the assemblage. Overall survival was highly variable, ranging from c . 15 to 90%, and was related to life history, habitat quality, and hydrologic events. Survival, which varied significantly among species and over time, was consistently higher in the dense and species‐rich core of the mussel assemblage, relative to the periphery because substrates were consistently more stable in the core of the mussel bed relative to the periphery. Substrate movement during low flows was an order of magnitude lower in the core relative to the periphery, and survival was inversely related to stability of river substrates. Patterns in habitat‐specific survival indicate source–sink population dynamics such that mussels in the core habitat provide recruitment to the periphery, but mussels in the periphery are subject to unsustainably low survival; additional studies to track the source of recruitment in the periphery are needed to test this hypothesis. Growth rate did not vary significantly between core and peripheral areas but did vary by species. Growth rate (proportional change per year) declined with age, and was similar at mean age for A. plicata (0.016 per year), P. sintoxia (0.015 per year), and C. pustulosa (0.013 per year), but much lower for O. reflexa (0.008 per year). Effective management decisions for mussels requires a better understanding of how vital rates govern populations and how they vary across a suite of physical and biological factors. Information on how population vital rates vary among species and over time gives managers another tool to understand how mussels may respond to management actions such as habitat restoration projects. Given the importance of substrate stability inferred from this study, management actions that maintain or increase substrate stability are likely to result in high quality mussel assemblages and may restore a valuable component of ecosystem function in this region.

Minnesota, Wisconsin↗
USGS2025

Site-level connectivity identified from multiple sources of movement data to inform conservation of a migratory bird

Migratory birds depend on a suite of sites across their annual cycles, making them vulnerable to a wide variety of anthropogenic pressures. Current area-based conservation measures have been found inadequate to safeguard migratory birds, in part due to a lack of consideration for the connectivity between sites mediated by the movements of individuals. To address this issue, we develop a network analysis integrating different types of individual movement data for a migratory shorebird, the Black-tailed Godwit ( Limosa limosa ), across the East Atlantic Flyway. Leveraging metal-ring recoveries, colour-ring re-sightings and satellite tracking from over 10,000 individual godwits, we quantify variation in connectivity between sites across the migratory range, using two weighted metrics to address sampling biases. Colour-ring re-sightings provided the largest number of sites (70%) and links (60% and 43% per season) overall, followed by tracking data (50% of sites, 49% and 63% of links per season) and ring recoveries (25% of sites, <1% of links per season), with clear regional variation in datatype contributions. Sampling completeness of the network structure varied with longitude, with information particularly lacking in central and eastern countries of both Europe and Africa. We identified 49 sites playing a disproportionate role in the site network, each with direct connections to 48 (interquartile range 32–84) other sites, on average. Just 23 (47%) top sites are formally recognized for their international importance for Black-tailed Godwits, and 33 (67%) were robust to sampling incompleteness. Across all 1058 sites, 20% lacked protected area coverage, and per site, 44% (44% ± SD) of bird relocations fell within protected areas. Integrating multiple sources of data improved geographical coverage and completeness of the site network, allowing us to quantify the importance of sites in terms of connectivity across the flyway. Our results highlight shortcomings of existing area-based conservation measures and add value to ongoing efforts to identify important sites for migratory birds. Policy implications . The increasing availability of individual movement data provides valuable opportunities to reveal the inter-dependence of sites used by migratory species, which can help identify priority areas and facilitate flyway-scale management.

Journal of Applied Ecology↗
USGS2007

The roles of physical habitat in reproduction and survival of pallid sturgeon and shovelnose sturgeon in the Lower Missouri River, progress 2005–06: Chapter D in Factors affecting the reproduction, recruitment, habitat, and population dynamics of pallid sturgeon and shovelnose sturgeon in the Missouri River

This report documents progress on three related components of habitat assessments in the Lower Missouri River during 2005–06. The habitat-use component links this research directly to sturgeon ecology research described in other chapters. The habitat availability and habitat dynamics assessments provide physical context for the ecological research. Results from 2005 to 2006 indicate that the methods developed to assess habitat use, quality, quantity, and dynamics are appropriate and sufficiently accurate to address critical questions about sturgeon habitat on the Lower Missouri River. Preliminary analysis of habitats occupied by adult female shovelnose sturgeon indicates that migrating sturgeon do not select for depth but seem to select for lower than reach-averaged velocities and higher than reach-averaged velocity gradients. Data collected to compile, calibrate, and validate multidimensional hydraulic models in probable spawning reaches appear to be sufficient to support the modeling objectives. Monitoring of selected channel cross sections and long profiles multiple times during the year showed little change at the upstreammost reach over the range of flows measured during 2006, likely because of channel stability associated with an armored bed. Geomorphic changes documented at monitoring cross sections increased with distance downstream. Hydroacoustic substrate-class parameters documented systematic changes with discharge and with hydraulic environment across the channel. Similarly, bed velocity varied predictably with discharge and hydraulic environment, indicating its potential as an indicator of bedload sediment transport. Longitudinal profiles showed substantial downstream movement of dunes over the monitored discharges, as well as substantial within-year variability in dune size. Observations of geomorphic change during the moderate flow range of 2006 support the hypothesis that the magnitude of flow modifications under consideration on the Lower Missouri River will be sufficient to transport sediment and potentially modify spawning habitats.

Lower Missouri River↗
USGS2021

Integrating observations and models to determine the effect of seasonally frozen ground on hydrologic partitioning in alpine hillslopes in the Colorado Rocky Mountains, USA

This study integrated spatially distributed field observations and soil thermal models to constrain the impact of frozen ground on snowmelt partitioning and streamflow generation in an alpine catchment within the Niwot Ridge Long-Term Ecological Research site, Colorado, USA. The study area was comprised of two contrasting hillslopes with notable differences in topography, snow depth and plant community composition. Time-lapse electrical resistivity surveys and soil thermal models enabled extension of discrete soil moisture and temperature measurements to incorporate landscape variability at scales and depths not possible with point measurements alone. Specifically, heterogenous snowpack thickness (~0–4 m) and soil volumetric water content between hillslopes (~0.1–0.45) strongly influenced the depths of seasonal frost, and the antecedent soil moisture available to form pore ice prior to freezing. Variable frost depths and antecedent soil moisture conditions were expected to create a patchwork of differing snowmelt infiltration rates and flowpaths. However, spikes in soil temperature and volumetric water content, as well as decreases in subsurface electrical resistivity revealed snowmelt infiltration across both hillslopes that coincided with initial decreases in snow water equivalent and early increases in streamflow. Soil temperature, soil moisture and electrical resistivity data from both wet and dry hillslopes showed that initial increases in streamflow occurred prior to deep soil water flux. Temporal lags between snowmelt infiltration and deeper percolation suggested that the lateral movement of water through the unsaturated zone was an important driver of early streamflow generation. These findings provide the type of process-based information needed to bridge gaps in scale and populate physically based cryohydrologic models to investigate subsurface hydrology and biogeochemical transport in soils that freeze seasonally.

Colorado↗
USGS2016

Do intracoelomic telemetry transmitters alter the post-release behaviour of migratory fish?

Electronic tags have become a common tool in fish research, enhancing our understanding of how fish interact with their environment and move among different habitats, for estimating mortality and recording internal physiological states. An often-untested assumption of electronic tagging studies is that tagged fish are representative of untagged conspecifics and thus show &lsquo;normal&rsquo; behaviour (e.g. movement rates, swimming activity, feeding). Here, we use a unique data set for potamadromous walleye (Sander vitreus) in Lake Huron and Lake Erie tributaries to assess whether the lack of appropriate controls in electronic tagging could seriously affect behavioural data. We used fish tagged in previous years and compared their migratory behaviour during the spawning season to fish tagged in a current year at the same location. The objective of the study was to determine whether intracoelomic acoustic tag implantation altered downstream movement of walleye after spawning. Fish tagged in a given season travelled slower downstream from two river spawning sites than fish tagged in previous years. Fish tagged one or two years earlier showed no differences between each other in downstream travel time, in contrast to fish tagged in a given year. Our results support notions that standard collection and intracoelomic tagging procedures can alter short-term behaviour (i.e. days, weeks, months), and as such, researchers should use caution when interpreting data collected over such time periods. Further, whenever possible, researchers should also explicitly evaluate post-tagging effects on behaviour as part of their experimental objectives.

Maumee Bay, Saginaw Bay↗
USGS2022

Seasonal variability in macroinvertebrate assemblages in paired perennial and intermittent streams in Costa Rica

Ecological effects of flooding and drying events are relatively understudied in the Neotropics and less is known about these hydrological extremes in intermittent streams. Neotropical headwater streams in Costa Rica provide opportunities to evaluate the response of macroinvertebrate communities to seasonal changes in flow regime in relatively human undisturbed systems. We quantified the effects of seasonal flow variation on aquatic macroinvertebrate assemblages (i.e., density, richness, and functional traits) within two headwater streams with differing hydrological regimes (i.e., intermittent versus perennial), in the Pacific North of Costa Rica. We sampled macroinvertebrates monthly over a year in riffle and pool habitats. Non-metric multidimensional scaling (NMDS) analyses indicated differences in macroinvertebrate taxonomic richness and density between the two streams and riffle and pool habitats. We found that macroinvertebrates in the intermittent stream riffles had significantly higher richness during the dry season. We also found higher macroinvertebrate functional trait richness in the intermittent stream riffle habitats during the dry season. Our results may be explained by life history traits related to stream velocity preference or tolerance, short life cycles that limit exposure to disturbances, and dispersal capacities and feeding mechanisms that are dependent on water movement.

Hydrobiologia↗
USGS2023

Factors influencing autumn–winter movements of midcontinent Mallards and consequences for harvest and habitat management

Annual phenology and distributions of migratory wildlife have been noticeably influenced by climate change, leading to concerns about sustainable populations. Recent studies exploring conditions influencing autumn migration departure have provided conflicting insights regarding factors influencing the movements of Mallards ( Anas platyrhynchos ), a popular game species. We determined factors affecting timing and magnitude of long-distance movements of 97 juvenile Mallards during autumn-winter across the midcontinent of North America marked with implanted transmitters in North and South Dakota, 2018–2019. Factors influencing variation in movement timing, along with direction and magnitudes, depended on type of movement (i.e., regional [25–310 km], initial migration, or subsequent migration movements [>310 km]). Photoperiod influenced probability of initiating all movements, although the effect was most influential for regional movements. Minimum temperature most influenced initial migration events (probability of movement increased 29% for each 1°C decrease); favorable winds also increased likelihood of initial migration events. Probability of subsequent migration events increased 80% for each 1 cm increase in depth of snow. Subsequent migration movements also were 2.0 times more likely to occur on weekend days, indicating disturbance from humans may influence movements. Migration distances increased 166 km for each 1°C reduction in minimum temperature. We also observed markedly different autumn-winter distributions of marked birds between years. Median locations during autumn-winter 2018–2019 were ~250 km farther north and ~300 km farther west during mid-December–January compared to the same time in 2019–2020. Concurrently, harvest rates for marked females and males were 10% and 26% during autumn-winter 2018–2019 and 26% and 31% during autumn-winter 2019–2020. Climate-related changes may result in increasingly variable autumn-winter distributions, with implications for wildlife recreationalists, conservation planners, and harvest managers.

Ecology and Evolution↗
USGS2009

Sampling design considerations for demographic studies: a case of colonial seabirds

For the purposes of making many informed conservation decisions, the main goal for data collection is to assess population status and allow prediction of the consequences of candidate management actions. Reducing the bias and variance of estimates of population parameters reduces uncertainty in population status and projections, thereby reducing the overall uncertainty under which a population manager must make a decision. In capture-recapture studies, imperfect detection of individuals, unobservable life-history states, local movement outside study areas, and tag loss can cause bias or precision problems with estimates of population parameters. Furthermore, excessive disturbance to individuals during capture?recapture sampling may be of concern because disturbance may have demographic consequences. We address these problems using as an example a monitoring program for Black-footed Albatross (Phoebastria nigripes) and Laysan Albatross (Phoebastria immutabilis) nesting populations in the northwestern Hawaiian Islands. To mitigate these estimation problems, we describe a synergistic combination of sampling design and modeling approaches. Solutions include multiple capture periods per season and multistate, robust design statistical models, dead recoveries and incidental observations, telemetry and data loggers, buffer areas around study plots to neutralize the effect of local movements outside study plots, and double banding and statistical models that account for band loss. We also present a variation on the robust capture?recapture design and a corresponding statistical model that minimizes disturbance to individuals. For the albatross case study, this less invasive robust design was more time efficient and, when used in combination with a traditional robust design, reduced the standard error of detection probability by 14% with only two hours of additional effort in the field. These field techniques and associated modeling approaches are applicable to studies of most taxa being marked and in some cases have individually been applied to studies of birds, fish, herpetofauna, and mammals.

Ecological Applications↗