Mottled Ducks Research Articles

Human-Induced Range Expansions Result in a Recent Hybrid Zone between Sister Species of Ducks.

Landscapes are consistently under pressure from human-induced ecological change, often resulting in shifting species distributions. For some species, changing the geographical breadth of their niche space results in matching range shifts to regions other than those in which they are formally found. In this study, we employ a population genomics approach to assess potential conservation issues arising from purported range expansions into the south Texas Brush Country of two sister species of ducks: mottled (Anas fulvigula) and Mexican (Anas diazi) ducks. Specifically, despite being non-migratory, both species are increasingly being recorded outside their formal ranges, with the northeastward and westward expansions of Mexican and mottled ducks, respectively, perhaps resulting in secondary contact today. We assessed genetic ancestry using thousands of autosomal loci across the ranges of both species, as well as sampled Mexican- and mottled-like ducks from across overlapping regions of south Texas. First, we confirm that both species are indeed expanding their ranges, with genetically pure Western Gulf Coast mottled ducks confirmed as far west as La Salle county, Texas, while Mexican ducks recorded across Texas counties near the USA-Mexico border. Importantly, the first confirmed Mexican × mottled duck hybrids were found in between these regions, which likely represents a recently established contact zone that is, on average, ~100 km wide. We posit that climate- and land use-associated changes, including coastal habitat degradation coupled with increases in artificial habitats in the interior regions of Texas, are facilitating these range expansions. Consequently, continued monitoring of this recent contact event can serve to understand species' responses in the Anthropocene, but it can also be used to revise operational survey areas for mottled ducks.

Mottled ducks, feral mallards, and their hybrids in Florida

AbstractThe nonmigratory and endemic Florida mottled duck (Anas fulvigula fulvigula) is facing conservation threats from the combined effects of urbanization and introgressive hybridization with feral mallards (Anas platyrhynchos) and mallard x mottled duck hybrids. In the past, the status of the Florida mottled duck population was assessed during annual aerial surveys and most brown ducks (mottled ducks, mallards, and hybrids of them) detected during the survey would have been mottled ducks. But the release of domesticated mallards for aesthetic purposes has led to increases in the prevalence of mallards‐hybrids (mallards or mallard x mottled duck hybrids) throughout peninsular Florida, USA, and because it is impossible to differentiate among mottled ducks, female mallards, and hybrids during aerial surveys, helicopter surveys were halted in 2009 until state researchers could conduct a range‐wide study to determine what proportion of brown ducks are mottled ducks versus mallards‐hybrids. We used plumage keys and high‐resolution photography to categorize brown ducks from 557 wetland grid points as either mottled ducks or mallards‐hybrids. Of the 5,179 brown ducks categorized, 40.1% were mottled ducks and 59.9% were mallards‐hybrids. We used logistic regression analysis to model the interactive effect of a site's latitude and level of urbanization (urban gradient value within a 2‐km buffer) to generate a predictive raster surface (1‐km resolution) of the study area with values corresponding to the probability that a brown duck observed within a cell is a pure mottled duck. Predicted values will be used as correction factors when estimating final mottled duck population abundance from brown‐duck survey data. Additionally, the predictive raster surface will be used to identify wetlands where mottled ducks remain predominant so that these sites can be targeted for preservation. Overall, mallards‐hybrids outnumbered mottled ducks throughout most of peninsular Florida, especially in more urbanized regions, and their current prevalence rate presents a serious conservation threat, via hybridization, to extant mottled duck populations.

Impacts of Drone Flight Altitude on Behaviors and Species Identification of Marsh Birds in Florida

Unmanned aerial vehicles (hereafter drones) are rapidly replacing manned aircraft as the preferred tool used for aerial wildlife surveys, but questions remain about which survey protocols are most effective and least impactful on wildlife behaviors. We evaluated the effects of drone overflights on nontarget species to inform the development of a Florida mottled duck (MODU; Anas fulvigula fulvigula) survey. Our objectives were to (1) evaluate the effect of flight altitude on the behavior of marsh birds, (2) evaluate the effect of altitude on a surveyor’s ability to identify the species of detected birds, and (3) test protocols for upcoming MODU surveys. We flew 120 continuously moving transects at altitudes ranging from 12 to 91 m and modeled variables that influenced detection, species identification, and behavior of nontarget species. Few marsh birds were disturbed during drone flights, but we were unable to confidently detect birds at the two highest altitudes, and we experienced difficulties identifying the species of birds detected in video collected at 30 m. Our findings indicate that MODUs could be surveyed at altitudes as low as 12–30 m with minimal impact to adjacent marsh birds and that larger-bodied nontarget marsh species can be identified from videos collected during MODU drone surveys.

Qualitative value of information provides a transparent and repeatable method for identifying critical uncertainty.

Conservation decisions are often made in the face of uncertainty because the urgency to act can preclude delaying management while uncertainty is resolved. In this context, adaptive management is attractive, allowing simultaneous management and learning. An adaptive program design requires the identification of critical uncertainties that impede the choice of management action. Quantitative evaluation of critical uncertainty, using the expected value of information, may require more resources than are available in the early stages of conservation planning. Here, we demonstrate the use of a qualitative index to the value of information (QVoI) to prioritize which sources of uncertainty to reduce regarding the use of prescribed fire to benefit Eastern Black Rails (Laterallus jamaicensis jamaicensis), Yellow Rails (Coterminous noveboracensis), and Mottled Ducks (Anas fulvigula; hereafter, focal species) in high marshes of the U.S. Gulf of Mexico. Prescribed fire has been used as a management tool in Gulf of Mexico high marshes throughout the last 30+ years; however, effects of periodic burning on the focal species and the optimal conditions for burning marshes to improve habitat remain unknown. We followed a structured decision-making framework to develop conceptual models, which we then used to identify sources of uncertainty and articulate alternative hypotheses about prescribed fire in high marshes. We used QVoI to evaluate the sources of uncertainty based on their Magnitude, Relevance for decision-making, and Reducibility. We found that hypotheses related to the optimal fire return interval and season were the highest priorities for study, whereas hypotheses related to predation rates and interactions among management techniques were lowest. These results suggest that learning about the optimal fire frequency and season to benefit the focal species might produce the greatest management benefit. In this case study, we demonstrate that QVoI can help managers decide where to apply limited resources to learn which specific actions will result in a higher likelihood of achieving the desired management objectives. Further, we summarize the strengths and limitations of QVoI and outline recommendations for its future use for prioritizing research to reduce uncertainty about system dynamics and the effects of management actions.

Temporal variation and landcover influence survival in adult female mottled ducks

AbstractAdult survival is a key driver of waterfowl population growth and is subject to temporal and spatial variation. Mottled ducks (Anas fulvigula) are native to the Gulf Coast and peninsular Florida, USA, and have suffered population declines over the past decade, especially in Texas and Louisiana, USA. Although the cause of this decline is not well understood, previous research concluded variation in survival contributed to nearly a third of variation in the species' population growth rate. We used global positioning system‐groupe spécial mobile (GPS‐GSM) transmitters to study temporal and spatial variation in survival of adult female western Gulf Coast mottled ducks in southwestern Louisiana, 2017–2020. We evaluated weekly survival models parameterized with combinations of hunted and non‐hunted periods, biological seasons, and landcover types that were used by mottled ducks. There were 3 competitive survival models, and all contained 4 parameters that parsed the annual cycle into the non‐hunted period, first part of the general waterfowl season, and second part of the waterfowl season, and included the proportion of GPS locations in agricultural lands. Weekly survival was 0.979 during the first part of the general waterfowl hunting season, and 0.996 during the second part of the general waterfowl season. Daily survival rate increased with an increasing proportion of locations logged in agricultural lands. Annual survival rates were similar to other waterfowl that are not experiencing population declines, which suggests survival is not limiting population growth of mottled ducks along the western Gulf Coast. Managers should ensure the availability of refuge areas where hunting is prohibited during the first part of the general waterfowl season, when mottled ducks are at an increased risk of mortality, in addition to the targeted conservation of agricultural lands that provide cover and forage.

Evaluation of Light-Logging Geolocators to Study Mottled Duck Nesting Ecology

Abstract Geolocators are small devices that record and store time-stamped light levels that researchers typically use to approximate the latitude and longitude of small birds across the annual cycle. However, when geolocators are affixed to leg bands of larger-bodied birds, nest incubation by females interrupts the daily pattern of light and darkness. Thus, geolocators can provide information on nesting propensity, nest success, and renesting intensity; these demographic parameters are both difficult to measure unobtrusively and are critically important in determining population dynamics of birds, especially ducks. Here, we deployed 240 geolocators on mottled ducks Anas fulvigula in Louisiana and Texas in 2018–2019 to evaluate their utility in providing nesting data. During July 2018–January 2022, we recovered 16 geolocators from hunter-harvested birds, and learned of 6 other unreported recoveries, yielding a realized recovery rate of 7.1% (9.1% unrealized). Three of the recovered units provided breeding-season data. Two of these clearly indicated a single nest initiation in the early spring of 2019, and one of the units also logged an attempt in spring of 2020. Ducks incubated all three nests for approximately a month, suggesting that they all successfully hatched. The final geolocator logged five putative nest attempts over the course of 2 y. In 2019, both attempts were unsuccessful (incubated ≤ 10 d). In 2020, we documented three attempts spanning 20 February–10 June, all of which appeared to have failed. For all failed attempts, the hen left the nest at dusk or overnight and did not return, which is suggestive of mammalian predation. Geolocators successfully provided information on breeding-season activities of mottled ducks, and we documented renesting rates following nest depredation. However, we achieved a smaller sample size than anticipated (three usable returns), resulting in an effective cost of $11,800 per usable return. Where possible in other species, capturing birds immediately prior to the breeding season, and improvements to geolocator attachment have the potential to improve recovery rates and increase cost effectiveness of the technique.

Mottled Duck introductions to South Carolina: The ugly, the bad, and the good?

Translocations or other movements of wildlife sometimes accomplish their intended objectives, but unforeseen consequences may arise and disrupt locally adapted ecological communities, restructure or dilute genetic integrity of populations or subspecies of the moved organism, and otherwise negatively influences a species’ long‐term fitness. Two historical populations of Mottled Ducks (Anas fulvigula) exist and are endemic to (1) Mexico and the West‐Gulf Coast (A. f. maculosa) regions of the United States and (2) Florida (A. f. fulvigula). From 1975 to 1983, 1285 Mottled Ducks from Florida, Louisiana, and Texas were released to coastal South Carolina, primarily to ultimately establish a legally harvestable population. This movement stirred mixed reactions amid the conservation community. Contemporary information suggests an increasing Mottled Duck population in South Carolina and possibly dispersing into Georgia. Herein, I objectively discuss the potential consequences of this new population per the birds’ evolution, ecology, and management. Ultimately, I suggest that this translocation is a long‐term benefit to the species.

Leveraging community science data for population assessments during a pandemic.

The COVID-19 pandemic has disrupted field research programs, making conservation and management decision-making more challenging. However, it may be possible to conduct population assessments using integrated models that combine community science data with existing data from structured surveys. We developed a space-time integrated model to characterize spatial and temporal variability in population distribution. We fit our integrated model to 10 years of eBird (2010-2020) and 9 years of aerial survey (2010-2019) Mottled Duck count data to forecast 2020 population size along the western Gulf Coast of Texas and Louisiana. Estimates of Mottled Duck abundance were similar in magnitude to estimates calculated using previous methods but were more precise and showed evidence of a declining population. The spatial distribution for Mottled Ducks each year was characterized by several concentrations of relatively high abundance, although the location of these abundance "hotspots" varied over time. Expected abundance was higher for areas with a higher proportion of area covered by marsh habitat. By leveraging large-scale community science data, we were able to conduct a population assessment despite the disruption in structured surveys caused by the pandemic. As participation in community science platforms continues to increase, we anticipate modeling frameworks, like the integrated model we developed here, will become increasingly useful for informing conservation and management decision-making.

Survival of western Gulf Coast Mottled Ducks (Anas fulvigula) in the path of a Category 4 hurricane.

Tropical cyclones are the most powerful storms on earth, causing catastrophic damage to human lives and infrastructure. Hurricanes also cause wildlife mortality when they make landfall, but the severity of these effects is difficult to quantify because data collection is either logistically impossible or deprioritized in the wake of human tragedy. On August 27, 2020, Hurricane Laura made landfall in southwestern Louisiana with maximum sustained winds of 241 kph (150 mph), making it one of the most powerful storms to strike the mainland United States. Hurricane Laura passed directly over the core breeding range of the western Gulf Coast population of Mottled Duck (Anas fulvigula), during a time when many adult birds were undergoing a simultaneous wing feather molt and were flightless. We used GPS‐GSM telemetry data to evaluate survival rates of adult female Mottled Ducks in late summer 2020 (bracketing August 27 by one month on either side) relative to the same period in 2018 and 2019. Mortality was lower in 2018 (12 out of 29; 41%) and 2019 (8 out of 28; 29%) than in 2020 (12 out of 18; 67%), and 7 out of 12 mortalities documented in 2020 occurred when Hurricane Laura made landfall. Survival analyses in program MARK confirmed lower survival probability in 2020, but there was overlap in 85% confidence intervals in all years. This single storm resulted in the death of ~40% of all marked birds in our sample, suggesting that hurricanes have the potential to influence population demographics. In addition, Hurricane Laura resulted in widespread habitat loss and degradation that has reduced available nesting habitat in 2021, and possibly for years to come. The acute and chronic effects of hurricanes may exacerbate Mottled Duck population declines, which may worsen in the face of increasingly frequent and more severe tropical storms.

Atmospheric circulation regimes for prescribed burns along the U.S. Gulf of Mexico coast

The regional-to-synoptic-scale steering atmospheric circulation is important for advecting energy, mass, and momentum across space, with the near-surface wind being the local manifestation of this circulation. The local winds can affect phenomena of economic, ecological, and/or aesthetic values, such as bird migrations and prescribed burns to restore bird habitats. The purpose of this research is to classify the days from 1979 to 2018 based on circulation patterns near the surface (i.e., 1000-hPa) and at the highest level of airflow affecting bird migration (i.e., 700-hPa), across the Gulf Coast region of the United States. The resulting patterns, derived from Ward's clustering method on rotated principal component scores, are used as input in a fire management plan to restore niches for bird species such as black and yellow rails and mottled ducks. Results suggest that for the (near-surface) 1000-hPa level, a classification system consisting of eight circulation types maximizes the between-group variability while minimizing the within-group variability, with a total of 95.8 percent of the dataset variance explained, and reasonable correspondence with existing manual, subjective and semi-automated techniques. At the 700-hPa level, a system of eight circulation types was derived, explaining 95.05 percent of the dataset variance. In general, the western U.S. Gulf of Mexico arc is more likely than the eastern to respond to synoptic control in the form of weather types, while the eastern region may have more influence from local-to-meso-scale land and sea breezes. These results will assist in optimizing the success of controlled burn conditions while enhancing efforts to minimize advection to populated areas.

Projected impact of sea-level rise and urbanization on mottled duck (Anas fulvigula) habitat along the Gulf Coast of Louisiana and Texas through 2100

Coastal wetlands along the Gulf of Mexico support a wide diversity of wildlife, are important nurseries for sport and commercial fisheries, provide erosion and flood control, and serve many other ecological functions and services. These marshes have been declining in area and degrading at alarming rates since the 1930s. Effective conservation planning is vital to protect these ecosystems, but decision makers often lack knowledge of expected future conditions to strategically target conservation actions. To address this issue, we focus on a species of conservation concern, the mottled duck (Anas fulvigula), that resides year-round in the coastal marshes of the Gulf of Mexico. We used location data collected from radiomarked hen mottled ducks from 2006 to 2011 to create an ensemble model of habitat selection for 2010. We then projected future habitat states using models of sea-level rise and human development. By combining future predictions with our ensemble model, we predict future habitat for mottled ducks through 2100, in 20-year time steps beginning with 2020. Sea-level rise models predicted reductions in coastal marsh habitats and our ensemble model predict corresponding declines in overall habitat quantity and quality for mottled ducks, with the largest rate of habitat loss predicted within the Chenier Plain of Louisiana, USA at 71%. In some areas, particularly the Texas Mid-Coast, USA, future urbanization and human development is expected to reduce the ability of wetland habitat to migrate inland with rising sea-levels. Our results also highlight areas of coastal marsh particularly vulnerable to sea-level rise; and conversely, identify areas most likely to persist into the future that could be targeted for habitat conservation to help mottled ducks persist on the landscape.

Population Genetics of a Translocated Population of Mottled Ducks and Allies

ABSTRACTTranslocating species is an important management tool to establish or expand the range of species. Success of translocations requires an understanding of potential consequences, including whether a sufficient number of individuals were used to minimize founder effects and if interspecific hybridization poses a threat. We provide an updated and comprehensive genetic assessment of a 1970s–1980s translocation and now established mottled duck (Anas fulvigula) population in South Carolina, USA. In addition to examining the population genetics of these mottled ducks, we simulated expected genetic assignments for generational hybrids (F1–F10), permitting formal purity assignment across samples to identify true hybrids and establish hybridization rates. In addition to wild mallards (A. platyrhynchos), we tested for presence of hybrids with migrant American black ducks (A. rubripes) and released domestic game‐farm mallards (A. p. domesticus). We used wild reference populations of North American mallard‐like ducks and sampled game‐farm mallards from 2 sites in South Carolina that could potentially interbreed with mottled ducks. Despite 2 different subspecies of mottled duck (Florida [A. f. fulvigula] and the Western Gulf Coast [A. f. maculatlus]) used in original translocations, we determined the gene pool of the Western Gulf Coast mottled duck was overwhelmingly represented in South Carolina's current population. We found no evidence of founder effects or inbreeding and concluded the original translocation of 1,285 mottled ducks was sufficient to maintain current genetic diversity. We identified 7 hybrids, including an F1 and 3 late‐staged (i.e., F2–F3 backcrosses) mottled duck × black duck hybrids, 1 F2‐mottled duck backcrossed with a wild mallard, and 2 F3‐mottled ducks introgressed with game‐farm mallard. We estimated a 15% hybridization rate in our mottled duck dataset; however, the general lack of F1 and intermediate hybrids were inconsistent with scenarios of high hybridization rates or presence of a hybrid swarm. Instead, our results suggested a scenario of infrequent interspecific hybridization between South Carolina's mottled ducks and congeners. We concluded that South Carolina's mottled duck population is sufficiently large now to absorb current hybridization rates because 85% of sampled mottled ducks were pure. These results demonstrate the importance in managing and maintaining large parental populations to counter hybridization. As such, future population management of mottled ducks in South Carolina will benefit from increased geographical and continued sampling to monitor hybridization rates with closely related congeners. We also suggest that any future translocations of mottled ducks to coastal South Carolina should originate from the Western Gulf Coast. © 2021 The Wildlife Society.

Breeding Ecology of Mottled Ducks: A Review

ABSTRACTMottled ducks (Anas fulvigula) are endemic to the Gulf Coast of North America, and their range stretches from Alabama to the Laguna Madre of Mexico, with a distinct population in peninsular Florida and an introduced population in South Carolina. As one of the few non‐migratory ducks in North America, mottled ducks depend on a variety of locally available habitat throughout the annual cycle, and threats to these landscapes may affect mottled ducks more acutely than migratory species. Annual population monitoring has revealed declines in mottled duck populations in Texas and Louisiana since 2008, and the genetic integrity of the Florida population has been muddled by the presence of large numbers of feral mallards (Anas platyrhynchos) resulting in hybridization. Similar to other closely related dabbling ducks, mottled duck populations are influenced by recruitment and breeding season survival, so changes in these factors may contribute to population decline. Accordingly, researchers have attempted to address various aspects of mottled duck breeding season ecology and population dynamics since the 1950s. We conducted a literature review on this topic by searching a combination of key terms using Google Scholar, including mottled duck, nesting ecology, habitat use, breeding incidence, nest success, brood, and breeding season survival, and followed citation trees to eventually aggregate information from nearly 50 publications on mottled duck breeding ecology. Our review concluded that mottled ducks use brackish and intermediate coastal marsh, including managed impoundments, and agricultural land during the breeding season. Their nests can be found in pastures, levees, dry cordgrass marsh, cutgrass marsh, spoil banks, and small islands. Nesting propensity and nest success estimates are often lower than other waterfowl species that are characterized by stable or increasing populations. Broods use wetlands composed of a mix of open water with submerged and emergent vegetation. Breeding season survival is higher for the Florida population than the western Gulf Coast population, but adult survival in both geographies is comparable to (or higher than) that of other dabbling duck species. Breeding habitat use, breeding season survival, and nest‐site selection and success have been studied extensively in mottled ducks, whereas information on nesting propensity, renesting intensity, and post‐hatch ecology is lacking. © 2021 The Wildlife Society.

Variation in Survival and Harvest Rates in Florida Mottled Duck

ABSTRACTThe Florida mottled duck (Anas fulvigula fulvigula) inhabits a relatively small range of approximately 90,000 km2 within peninsular Florida, USA, and is threatened by habitat loss and genetic introgression with feral mallards (Anas platyrhynchos). Moreover, the Florida mottled duck population status has not been assessed for more than a decade. We used band‐recovery and recapture data from 2000–2013 to examine geographic and demographic factors that influence the survival of Florida mottled ducks and to determine whether survival and harvest probabilities have changed over time. Mean survival probabilities were higher for birds banded in the southern portion of their Florida range than for those banded in the northern portion and higher for adult males than for adult females in both areas. Harvest probabilities increased in the northern extent of its range in Florida for adults and juveniles and remained relatively constant in the southern portion of its range during the study period. Mean harvest probabilities for adult males in both areas were higher than for adult females. Mean harvest probability for juvenile females was higher than that for juvenile males in the north but was similar between the sexes in the south. Our results suggest that mortality rates are generally greater in the northern portion of the Florida mottled duck range because of regional differences in habitat distribution and permanence and in how mottled ducks and humans use wetlands in these areas. We suggest increasing conservation efforts in the north portion of the Florida mottled duck range and improving inferences from leg banding by incorporating live recapture data. © 2020 The Wildlife Society.

Distribution of contaminants in the environment and wildlife habitat use: a case study with lead and waterfowl on the Upper Texas Coast.

The magnitude and distribution of lead contamination remain unknown in wetland systems. Anthropogenic deposition of lead may be contributing to negative population-level effects in waterfowl and other organisms that depend on dynamic wetland habitats, particularly if they are unable to detect and differentiate levels of environmental contamination by lead. Detection of lead and behavioral response to elevated lead levels by waterfowl is poorly understood, but necessary to characterize the risk of lead-contaminated habitats. We measured the relationship between lead contamination of wetland soils and habitat use by mottled ducks (Anas fulvigula) on the Upper Texas Coast, USA. Mottled ducks have historically experienced disproportionate negative effects from lead exposure, and exhibit a unique nonmigratory life history that increases risk of exposure when inhabiting contaminated areas. We used spatial interpolation to estimate lead in wetland soils of the Texas Chenier Plain National Wildlife Refuge Complex. Soil lead levels varied across the refuge complex (0.01-1085.51 ppm), but greater lead concentrations frequently corresponded to areas with high densities of transmittered mottled ducks. We used soil lead concentration data and MaxENT species distribution models to quantify relationships among various habitat factors and locations of mottled ducks. Use of habitats with greater lead concentration increased during years of a major disturbance. Because mottled ducks use habitats with high concentrations of lead during periods of stress, have greater risk of exposure following major disturbance to the coastal marsh system, and no innate mechanism for avoiding the threat of lead exposure, we suggest the potential presence of an ecological trap of quality habitat that warrants further quantification at a population scale for mottled ducks.

First documented case of overwater nesting by Mottled Ducks (Anas fulvigula)

ABSTRACT The Mottled Duck (Anas fulvigula) is a range-restricted species endemic to the western Gulf Coast states and peninsular Florida. As a year-round resident, it relies on coastal marsh and ne...

Survival, Recovery, and Reproductive Success of Mottled Ducks on the Upper Texas Coast

Anas fulvigula (Mottled Duck) has experienced long-term population declines due to habitat loss and other anthropogenic factors. Our objectives were to (1) generate annual survival and recovery estimates, while examining the influence of age and sex, and (2) examine the influence of rainfall and drought on reproductive success. We followed the Brownie approach using the RMark package in R to analyze 4967 bandings and 705 recoveries from 2004–2015. We examined linear and curvilinear relationships between precipitation variables and a reproductive index. Hatch-year (HY) males had the highest annual recovery probability, while after-hatch-year (AHY) females had the lowest. Annual survival varied predominately by sex but also with age. Hatch-year females had the lowest estimate of survival, while after-hatch-year males had the highest. Total rainfall during peak nesting season showed a weak negative relationship with our reproductive success index (β = -0.0085, 95% CI: -0.0240, 0.0070), and was our only competitive model besides the null. Annual survival and recovery estimates were similar to other studies on Mottled Ducks. Our reproductive success analysis was inconclusive in that either there is no effect of precipitation or the measures we used for the reproduction index or the predictor variables were inadequate.

Seasonal habitat selection and movements by mottled ducks

ABSTRACTMottled ducks (Anas fulvigula) were released by the South Carolina Department of Natural Resources (SCDNR) in South Carolina, USA, during 1975–1983 and expanded into Georgia, USA, in the 1990s. Banding data suggest that birds marked in Georgia are often harvested in other states. Because the South Carolina reintroduced population was able to expand into Georgia via long‐distance dispersal, a more thorough understanding of mottled duck spatial ecology in Georgia and South Carolina is needed to direct future management decisions to accommodate expanding duck populations. We used global positioning system (GPS) telemetry to investigate movements and habitat selection by 47 mottled ducks (17 males, 30 females) during 4 seasons from 2013–2016. Mean seasonal home ranges varied from 2,002–4,598 ha across sexes and seasons. We found mean distances moved within seasonal ranges varied from 3.5–11.3 km/day for birds captured in Georgia, and 1.3–5.6 km/day for those captured in South Carolina. We observed 23 excursions, in which individuals left established seasonal ranges for >6 hours and moved ≥5 km; these excursions ranged from 5 km to 139.5 km. We documented 5 dispersals ranging from 52.6 km to 245.8 km. We also documented several long‐distance movements, with 7 birds captured in Georgia moving to South Carolina and 2 moving to Florida, USA. These movements suggest mottled ducks in South Carolina and Georgia may constitute a single population. Notably, we observed dispersal and long‐distance movements only from birds marked in Georgia, suggesting that habitat may be a limiting factor along the Georgia coast. We quantified third‐order selection for mottled ducks and found seasonal selection for managed impoundments and avoidance of palustrine emergent marsh during breeding and teal seasons. Managed impoundments were limited to 4 river systems along coastal Georgia and South Carolina, resulting in much of the coastal wetlands in both states being unused by mottled ducks. We suggest the Georgia Department of Natural Resources (GADNR) and SCDNR work cooperatively to manage mottled ducks and their habitats by focusing efforts to create and manage impoundments throughout the Santee, Savannah, Altamaha, and Ashepoo‐Combahe‐Edisto (ACE) river basins in coastal Georgia and South Carolina where we documented use. © 2018 The Wildlife Society.

Foraging by Mottled Ducks (Anas fulvigula) in a dry agriculture field during winter: a novel observation

ABSTRACT On 9 December 2016, we observed 10 Mottled Ducks (Anas fulvigula) foraging in a harvested, dry cornfield in south Texas. Several North American waterfowl species in the genus Anas commonly feed in dry agricultural fields; however, this foraging strategy has not been documented in Mottled Ducks during winter prior to this observational account. As corn acreage increases in coastal Texas in conjunction with declining acreage of wetland habitats, Mottled Ducks may opportunistically forage in dry agricultural fields more frequently.

Decision support tool: Mottled duck habitat management and conservation in the Western Gulf Coast

The Western Gulf Coast provides important habitat for migratory and resident waterfowl. The mottled duck (Anas fulvigula) relies on this region for all of its life-cycle events. Its relatively small population, limited worldwide range, and generally declining population trajectory has earned it a “Red” status on the Audubon WatchList and is a species of concern among state and federal agencies. The Western Gulf Coast (WGC) mottled duck population decline is believed to be primarily caused by the historical conversion and degradation of coastal wetlands and native prairie, and recent declines in cultivated rice. There is general agreement among experts that negative impacts to nesting and brood-rearing habitat are the most important threats to the WGC mottled duck population and increasing recruitment is essential to the growth and sustainability of the population.Our goal was to use available knowledge of mottled duck nesting and brood-rearing requirements to develop a model to aid managers in targeting areas for conservation and management. We developed four spatially explicit models that: 1) identify and prioritize existing mottled duck nesting habitat for conservation (e.g., protection or maintenance); 2) identify and prioritize existing mottled duck brood-rearing habitat for conservation; 3) identify and prioritize areas for grassland establishment; and 4) identify and prioritize wetland basins for freshwater enhancement. Spatial models revealed that only 6 km2 and 9 km2 of nesting and brood-rearing habitat, respectively, were identified as highest priority (top 10%) for conservation in the WGC. Brood habitat was identified as potentially limiting recruitment in the Texas Mid Coast and the Laguna Madre subregions of our study area, whereas grassland habitat was potentially limiting recruitment in Chenier Plain and Mississippi River Coastal Wetlands subregions. Spatial models also revealed that there is a high density of areas of high priority for grassland establishment inland in Texas and Louisiana. Likewise, there is a high density of wetland basins of high priority for freshwater enhancement throughout coastal Louisiana and the upper Texas coast.We used two separate measures to assess the performance of our Mottled Duck Decision Support Tool (hereafter MODU-DST) and found that it adequately identified patch suitability, as defined by our model, with ≥79% accuracy. Using data from the Cooperative Breeding Mottled Duck Survey, we also found that breeding mottled ducks were using landscapes with optimal spatial arrangement of nesting and brood-rearing habitat, which is reflected by higher mean priority rankings of nesting and brood-rearing habitat in the landscape.