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At least 631 records · Page 35Linked to original sources

USGS2017

Control of invasive weeds with prescribed burning

Prescribed burning has primarily been used as a tool for the control of invasive late-season annual broadleaf and grass species, particularly yellow starthistle, medusahead, barb goatgrass, and several bromes. However, timely burning of a few invasive biennial broadleaves (e.g., sweetclover and garlic mustard), perennial grasses (e.g., bluegrasses and smooth brome), and woody species (e.g., brooms and Chinese tallow tree) also has been successful. In many cases, the effectiveness of prescribed burning can be enhanced when incorporated into an integrated vegetation management program. Although there are some excellent examples of successful use of prescribed burning for the control of invasive species, a limited number of species have been evaluated. In addition, few studies have measured the impact of prescribed burning on the long-term changes in plant communities, impacts to endangered plant species, effects on wildlife and insect populations, and alterations in soil biology, including nutrition, mycorrhizae, and hydrology. In this review, we evaluate the current state of knowledge on prescribed burning as a tool for invasive weed management.

Weed Technology↗

USGS2005

Habitat and sex differences in physiological condition of breeding Southwestern Willow Flycatchers ( Empidonax traillii extimus )

The Southwestern Willow Flycatcher ( Empidonax traillii extimus ; here- after “flycatcher”) is a federally listed endangered species that breeds in densely vegetated riparian habitats dominated by native and exotic plants, including introduced monotypic saltcedar (Tamarix ramosissima) . Some workers have theorized that saltcedar is unsuitable habitat for the flycatcher, primarily because it generally supports a smaller and less diverse invertebrate community (the flycatcher's food base) than native habitats (e.g. Salix spp.). However, differences in insect communities between native and saltcedar habitats are not proof that saltcedar habitats are inferior. The only way to evaluate whether the habitats differ in dietary or energetic quality is to document actual food limitation or its manifestations. Measurements of an individual's body condition and metabolic state can serve as indicators of environmental stressors, such as food limitation and environmental extremes. We captured 130 flycatchers breeding in native and saltcedar habitats in Arizona and New Mexico and measured 12 variables of physiological condition. These variables included body mass, fat level, body condition index, hematocrit, plasma triglycerides, plasma free fatty acids and glycerol, plasma glucose and beta-hydroxybutyrate, plasma uric acid, total leukocyte count, and heterophil-to-lymphocyte ratio. We found substantial sex-based differences in the condition of male and female flycatchers. Ten of the 12 measures of physiological condition differed significantly between the sexes. In all cases where male and female condition differed (except mass), the differences suggest that males were in poorer condition than females. We found few habitat-based differences in flycatcher condition. Only 3 of the 12 physiological condition indices differed significantly between habitats. Our data show that, at least in some parts of the flycatcher's range, there is no evidence that flycatchers breeding in saltcedar habitats exhibit poorer nutritional condition or are suffering negative physiological affects.

The Auk↗

USGS2013

Roost selection by western long-eared myotis (Myotis evotis) in burned and unburned piñon–juniper woodlands of southwestern Colorado

All 16 species of bats known to occur in western Colorado are found at Mesa Verde National Park (MVNP) in the southwestern United States. Since 1996, wildfires have burned more than 70% of MVNP (> 15,000 ha), potentially altering food and roosting resources for bats. During the summers of 2006–2007, we investigated roost use by reproductive female western long-eared myotis ( Myotis evotis ). We located 33 bat roosts in rock crevices and 1 in a juniper snag. All but 2 of the roosts were in unburned habitat. Bats roosted alone or in small groups (≤3 individuals) and switched roosts frequently (1–7 roosts per bat, median = 1.5 roosts per bat, SE = 0.5 roosts per bat). We compared occupied roosts with randomly selected unoccupied crevices and used an information theoretic approach to determine which variables were most important in determining roost use at microhabitat and landscape scales. At the microhabitat scale, maternity roosts were higher above the ground and deeper than random, unoccupied rock crevices. At the landscape scale, roosts were closer to water and farther from burned habitat than random crevices, providing reproductive female M. evotis with the best opportunities to drink and forage for insects. Tree roosts are apparently not a vital resource for reproductive female M. evotis during the summer months at our study site, presumably because of the extensive availability of rock crevices. Understanding site-specific roosting behavior is important for proper management of bat populations because differences can exist between geographic regions, even among areas with similar plant communities.

Colorado↗

USGS2004

Diets of insectivorous birds along the Colorado River in Grand Canyon, Arizona

We examined diets of six insectivorous bird species ( n = 202 individuals) from two vegetation zones along the Colorado River in Grand Canyon National Park, Arizona, 1994. All bird species consumed similar quantities of caterpillars and beetles, but use of other prey taxa varied. Non-native leafhoppers ( Opsius stactagolus ) specific to non-native tamarisk ( Tamarix chinensis ) substantially augmented Lucy's Warbler ( Vermivora luciae ) diets (49%), while ants comprised 82% of Yellow-breasted Chat ( Icteria virens ) diets. Yellow Warbler ( Dendroica petechia ) diets were composed of 45% aquatic midges. All bird species consumed the non-native leafhopper specific to tamarisk. Comparison of bird diets with availability of arthropod prey from aquatic and terrestrial origins showed terrestrial insects comprised 91% of all avian diets compared to 9% of prey from aquatic origin. Seasonal shifts in arthropod prey occurred in diets of three bird species, although no seasonal shifts were detected in arthropods sampled in vegetation indicating that at least three bird species were not selecting prey in proportion to its abundance. All bird species had higher prey overlap with arthropods collected in the native, mesquite-acacia vegetation zone which contained higher arthropod diversity and better prey items (i.e., Lepidoptera). Lucy's Warbler and Yellow Warbler consumed high proportions of prey items found in greatest abundance in the tamarisk-dominated vegetation zone that has been established since the construction of Glen Canyon Dam. These species appeared to exhibit ecological plasticity in response to an anthropogenic increase in prey resources.

Arizona↗

USGS2010

Judging a brook by its cover: The relation between ecological condition of a stream and urban land cover in new England

The US Geological Survey conducted an urban land-use study in the New England Coastal Basins (NECB) area during 2001 to determine how urbanization relates to changes in the ecological condition of streams. Thirty sites were selected that differed in their level of watershed development (low to high). An urban intensity value was calculated for each site from 24 landscape variables. Together, these 30 values reppresented a gradient of urban intensity. Among various biological, chemical, and physical factors surveyed at each site, benthic invertebrate assemblages were sampled from stream riffles and also from multiple habitats along the length of the sampling reach. We use some of the NECB data to derive a four-variable urbanintensity index (NECB-UII), where each variable represents a distinct component of urbanization: increasing human presence, expanding infrastructure, landscape development, and riparian vegetation loss. Using the NECB-UII as a characterization of urbanization, we describe how landscape fragmentation occurs with urbanization and how changes in the invertebrate assemblages, represented by metrics of ecological condition, are related to urbanization. Metrics with a strong linear response included EPT taxa richness, percentage richness of non-insect taxa, and pollution-tolerance values. Additionally, we describe how these relations can help in estimating the expected condition of a stream for its level of urbanization, thereby establishing a baseline for evaluating possible affects from specific point-source stressors.

Northeastern Naturalist↗

USGS2013

Diet of the eastern mudminnow (Umbra pygmaea DeKay) from two geographically distinct populations within the North American native range

Umbra pygmaea (Eastern Mudminnow) is a freshwater species common in Atlantic slope coastal lowlands from southern New York to northern Florida and is typical of slow-moving, mud-bottomed, and highly vegetated streams, swamps, and small ponds. We examined its seasonal food habits at the Great Swamp National Wildlife Refuge (NWR), NJ and at the Croatan National Forest, NC. A total of 147 Eastern Mudminnow from 35–112 mm TL and 190 Eastern Mudminnow from 22–89 mm TL were examined from these sites, respectively. At both locations, we found it to be a bottom-feeding generalist that consumes cladocerans, ostracods, chironomid larvae, coleopteran larvae, and other insects and crustaceans. Ostracods were most common in the diet at the Great Swamp NWR and occurred in 62% ± 2.5% of the stomachs with food. At Croatan National Forest, chironomid larvae were most common and occurred in 66.7% ± 15.8% of the stomachs. There were no statistically significant differences in diet composition between the sites during the winter, summer, and fall. However, when compared on an annual basis, Jaccard’s Index (θ J = 0.636, P = 0.05) suggested that the diet at the two study sites was significantly different. While we identified the same major food groups at both locations, the utilization of these food groups varied seasonally. Detritus was a major stomach content at both locations throughout the year. We also documented cannibalism during the summer season at both locations. The seasonal diet of the Eastern Mudminnow was similar to that of Umbra limi (Central Mudminnow) and Umbra krameri (European Mudminnow). Our findings here are the first quantitative examinations of seasonal differences in the diet of the Eastern Mudminnow within its native North American range.

Northeastern Naturalist↗

USGS2023

DNA metabarcoding-based evaluation of the diet of Big Brown Bats (Eptesicus fuscus) in the Mid-Atlantic region

High-throughput DNA sequencing can generate large genetic datasets in a cost-effective manner. Although the diet of Eptesicus fuscus (Big Brown Bat) has been studied widely in natural and rural systems using visual identification of prey items in feces, our aim was to more completely assess diet using a metabarcoding approach across a wide urban–natural landscape gradient in the mid-Atlantic region. Concordant with our expectations and previous Big Brown Bat diet studies from visual identification, we observed a high abundance of Coleoptera (beetles) relative to other insect orders. Although a possible improvement over visual techniques for studying food habits, we suggest caution in interpreting metabarcoding results in diet studies. We noted observations of environmental or contaminant taxa within these data, and designed a stringent filtering method that we used to eliminate these taxa, but that also removed previously documented prey taxa from our dataset.

Maryland, Pennsylvania, Virginia, West Virginia↗

USGS2025

Video evidence of a Red-eared Slider (Trachemys scripta elegans) preying upon a live Mallard (Anas platyrhynchos) duckling in Louisiana

Most animal matter in the diet of the omnivorous Trachemys scripta (Pond Slider) consists of invertebrate prey items such as insects, crustaceans, and mollusks, but often also includes fish and amphibians. Reptiles, birds, and mammals are less commonly reported, and even when found, it is usually unknown if they were captured alive, as Pond Sliders will certainly scavenge dead animals. Though it is well known that Chelydra serpentina (Snapping Turtle) will prey upon waterfowl from the water surface, reports of such encounters are seemingly rare in Pond Sliders. Here, we document with video evidence an adult female T. s. elegans (Red-eared Slider) emerging from the water to successfully take and drown an Anas platyrhynchos (Mallard) duckling.

Louisiana↗

USGS2005

Critical literature review of the evidence for unpalatability of amphibian eggs and larvae

We examined 142 papers, which contained 603 separate predator-prey trials, to investigate whether unpalatability is an important defense against predation for amphibian eggs and larvae. Although unpalatability is often cited as an antipredator defense, it was rarely demonstrated that 89% of the trials that we reviewed found prey to be palatable. The most extensively studied taxa, the genera Bufo and Rana , were diagnosed unpalatable at rates comparable to all other taxa. Diagnoses of unpalatability were not always consistent for a prey species across different predators and were influenced by experimental method. Despite these limitations and our conservative definition of unpalatability, several patterns emerged. First, across all taxonomic groups, eggs and hatchlings were unpalatable more often than mobile larval stages. Second, species that breed in temporary ponds were more likely to be palatable to fish predators than those that breed in permanent habitats. Third, fish and caudates were more likely to find amphibian prey unpalatable than insect predators. We conclude that unpalatability is rare, but when it occurs, it is a property of an ensemble (predator, prey, and alternative prey) and a life-history stage in a particular circumstance but is not a species-specific attribute. We suggest methods of experimentation that could strengthen future research on the palatability of amphibian eggs and larvae.

Journal of Herpetology↗

USGS2010

Red imported fire ant impacts on upland arthropods in Southern Mississippi

Red imported fire ants (Solenopsis invicta) have negative impacts on a broad array of invertebrate species. We investigated the impacts of fire ants on the upland arthropod community on 20???40 ha study sites in southern Mississippi. Study sites were sampled from 19972000 before, during, and after fire ant bait treatments to reduce fire ant populations. Fire ant abundance was assessed with bait transects on all sites, and fire ant population indices were estimated on a subset of study sites. Species richness and diversity of other ant species was also assessed from bait transects. Insect biomass and diversity was determined from light trap samples. Following treatments, fire ant abundance and population indices were significantly reduced, and ant species diversity and richness were greater on treated sites. Arthropod biomass, species diversity and species richness estimated from light trap samples were negatively correlated with fire ant abundance, but there were no observable treatment effects. Solenopsis invicta has the potential to negatively impact native arthropod communities resulting in a potential loss of both species and function.

American Midland Naturalist↗

USGS2014

Resource partitioning in two stream salamanders, Dicamptodon tenebrosus and Rhyacotriton cascadae, from the Oregon Cascade Mountains

We investigated the potential for resource partitioning between the Coastal giant salamander ( Dicamptodon tenebrosus ) and the Cascade torrent salamander ( Rhyacotriton cascadae ) by examining their diet and microhabitats in forest streams. Larval D. tenebrosus and R. cascadae fed primarily upon aquatic insect larvae. We found similar foods in larval and adult R. cascadae and combined these results. Dicamptodon larvae consumed ephemeropteran, plecopteran, and trichopteran larvae in about equal amounts whereas R. cascadae ate more trichopteran and less ephemeropteran larvae than D. tenebrosus . Diet of all R. cascadae overlapped more with smaller than larger sized D. tenebrosus larvae. Comparisons of diets with available foods indicated R. cascadae is more selective or more gape-limited in its feeding habits than D. tenebrosus larvae. The two salamanders differed in use of microhabitats in creeks, which may contribute to their diet differences.

Oregon↗

USGS2014

Habitat and food preferences of the endangered Palila (Loxioides bailleui) on Mauna Kea, Hawai'i

Seeds and flowers of the leguminous māmane ( Sophora chrysophylla ) tree are the primary food resource of the federally endangered Palila ( Loxioides bailleui ; Fringillidae: Drepanidinae), which is now restricted to dry subalpine woodland on Mauna Kea Volcano on the island of Hawai'i because of centuries of habitat degradation by non-native ungulates. Palila are morphologically and behaviorally adapted to consume mÄmane seeds by grasping seed pods with their feet and opening pods with stout bills and demonstrate limited ability to exploit alternative food resources. This degree of single species dependency is rare among birds and illustrates unique adaptations that also occurred in other Hawaiian species that are now extinct. In mixed-woodland with co-dominant naio ( Myoporum sandwicense ), Palila spent 1.7-3.9 times longer in māmane than in naio during foraging observations where naio was 1.3-4.6 times as dense as māmane. Naio fruit was readily available, but it comprised proportionally <11% of food items taken by Palila. Although māmane flowers were more abundant than māmane pods throughout this study except at one lower-elevation mixed-woodland site, Palila spent more time foraging on pods than flowers in both māmane woodland and mixed-woodland, but consumed more flowers than pods in mixed-woodland. Insects, which have been reported as an important component of the diet of Palila, were apparently taken rarely in this study. Protecting and restoring māmane in woodlands adjacent to the current range of Palila will benefit their recovery, allowing them to exploit increased food availability in areas of their former range.

Hawai'i↗

USGS2026

Post-hatch ecology, diet, and first migration of juvenile Alaskan Bar-tailed Godwits

Life stages between hatching and adult recruitment are poorly described for most migratory shorebird species and represent a critical knowledge gap in understanding long-term population dynamics. We conducted a pilot study on the Seward Peninsula, Alaska, to assess the feasibility of following juvenile Bar-tailed Godwits Limosa lapponica baueri from their breeding grounds to their non-breeding grounds in New Zealand and Australia. Radio-tracked broods were highly mobile and moved hundreds to thousands of meters per day. They used low-elevation wetlands with dense shrub cover when younger, and more open, tundra-dominated ridgetops when older. Using DNA metabarcoding analysis of fecal samples, we found that chick diet consisted largely of flying insects (e.g. Tenthredinidae and Ichneumonidae) and small gastropods and appeared to increase in diversity with chick age. We followed one brood to near-fledging (ca. 26 days old) and deployed 5-g satellite transmitters on three chicks. One of these subsequently moved to the Yukon-Kuskokwim Delta, from where it flew 11 days and an estimated 13,391 km to Tasmania, which is the longest non-stop flight recorded for landbirds. These results provide the first information on the ecology of pre- and post-fledging young Bar-tailed Godwits in Alaska, and will inform future efforts to study this important life stage.

Alaska↗

USGS2008

Spatial elements of mortality risk in old-growth forests

For many species of long-lived organisms, such as trees, survival appears to be the most critical vital rate affecting population persistence. However, methods commonly used to quantify tree death, such as relating tree mortality risk solely to diameter growth, almost certainly do not account for important spatial processes. Our goal in this study was to detect and, if present, to quantify the relevance of such processes. For this purpose, we examined purely spatial aspects of mortality for four species, Abies concolor , Abies magnifica , Calocedrus decurrens , and Pinus lambertiana , in an old-growth conifer forest in the Sierra Nevada of California, USA. The analysis was performed using data from nine fully mapped long-term monitoring plots. In three cases, the results unequivocally supported the inclusion of spatial information in models used to predict mortality. For Abies concolor , our results suggested that growth rate may not always adequately capture increased mortality risk due to competition. We also found evidence of a facilitative effect for this species, with mortality risk decreasing with proximity to conspecific neighbors. For Pinus lambertiana , mortality risk increased with density of conspecific neighbors, in keeping with a mechanism of increased pathogen or insect pressure (i.e., a Janzen-Connell type effect). Finally, we found that models estimating risk of being crushed were strongly improved by the inclusion of a simple index of spatial proximity. Not only did spatial indices improve models, those improvements were relevant for mortality prediction. For P. lambertiana , spatial factors were important for estimation of mortality risk regardless of growth rate. For A. concolor , although most of the population fell within spatial conditions in which mortality risk was well described by growth, trees that died occurred outside those conditions in a disproportionate fashion. Furthermore, as stands of A. concolor become increasingly dense, such spatial factors are likely to become increasingly important. In general, models that fail to account for spatial pattern are at risk of failure as conditions change.

Ecology↗

USGS2009

Delayed conifer mortality after fuel reduction treatments: Interactive effects of fuel, fire intensity, and bark beetles

Many low‐elevation dry forests of the western United States contain more small trees and fewer large trees, more down woody debris, and less diverse and vigorous understory plant communities compared to conditions under historical fire regimes. These altered structural conditions may contribute to increased probability of unnaturally severe wildfires, susceptibility to uncharacteristic insect outbreaks, and drought‐related mortality. Broad‐scale fuel reduction and restoration treatments are proposed to promote stand development on trajectories toward more sustainable structures. Little research to date, however, has quantified the effects of these treatments on the ecosystem, especially delayed and latent tree mortality resulting directly or indirectly from treatments. In this paper, we explore complex hypotheses relating to the cascade of effects that influence ponderosa pine (Pinus ponderosa) and Douglas‐fir (Pseudotsuga menziesii) mortality using structural equation modeling (SEM). We used annual census and plot data through six growing seasons after thinning and four growing seasons after burning from a replicated, operational‐scale, completely randomized experiment conducted in northeastern Oregon, USA, as part of the national Fire and Fire Surrogate study. Treatments included thin, burn, thin followed by burn (thin + burn), and control. Burn and thin + burn treatments increased the proportion of dead trees while the proportion of dead trees declined or remained constant in thin and control units, although the density of dead trees was essentially unchanged with treatment. Most of the new mortality (96%) occurred within two years of treatment and was attributed to bark beetles. Bark beetle‐caused tree mortality, while low overall, was greatest in thin + burn treatments. SEM results indicate that the probability of mortality of large‐diameter ponderosa pine from bark beetles and wood borers was directly related to surface fire severity and bole charring, which in turn depended on fire intensity, which was greater in units where thinning increased large woody fuels. These results have implications when deciding among management options for restoring ecosystem health in similar ponderosa pine and Douglas‐fir forests.

Ecological Applications↗

USGS2009

Species richness and occupancy estimation in communities subject to temporary emigration

Species richness is the most common biodiversity metric, although typically some species remain unobserved. Therefore, estimates of species richness and related quantities should account for imperfect detectability. Community dynamics can often be represented as superposition of species-specific phenologies (e. g., in taxa with well-defined flight [insects], activity [rodents], or vegetation periods [plants]). We develop a model for such predictably open communities wherein species richness is expressed as the sum over observed and unobserved species of estimated species-specific and site-specific occurrence indicators and where seasonal occurrence is modeled as a species-specific function of time. Our model is a multispecies extension of a multistate model with one unobservable state and represents a parsimonious way of dealing with a widespread form of 'temporary emigration.'' For illustration we use Swiss butterfly monitoring data collected under a robust design (RD); species were recorded on 13 transects during two secondary periods within <= 7 primary sampling periods. We compare estimates with those under a variation of the model applied to standard data, where secondary samples are pooled. The latter model yielded unrealistically high estimates of total community size of 274 species. In contrast, estimates were similar under models applied to RD data with constant (122) or seasonally varying (126) detectability for each species, but the former was more parsimonious and therefore used for inference. Per transect, 6 44 (mean 21.1) species were detected. Species richness estimates averaged 29.3; therefore only 71% (range 32-92%) of all species present were ever detected. In any primary period, 0.4-5.6 species present were overlooked. Detectability varied by species and averaged 0.88 per primary sampling period. Our modeling framework is extremely flexible; extensions such as covariates for the occurrence or detectability of individual species are easy. It should be useful for communities with a predictable form of temporary emigration where rigorous estimation of community metrics has proved challenging so far.

Ecology↗

USGS2009

When can efforts to control nuisance and invasive species backfire?

Population control through harvest has the potential to reduce the abundance of nuisance and invasive species. However, demographic structure and density-dependent processes can confound removal efforts and lead to undesirable consequences, such as overcompensation (an increase in abundance in response to harvest) and instability (population cycling or chaos). Recent empirical studies have demonstrated the potential for increased mortality (such as that caused by harvest) to lead to overcompensation and instability in plant, insect, and fish populations. We developed a general population model with juvenile and adult stages to help determine the conditions under which control harvest efforts can produce unintended outcomes. Analytical and simulation analyses of the model demonstrated that the potential for overcompensation as a result of harvest was significant for species with high fecundity, even when annual stage-specific survivorship values were fairly low. Population instability as a result of harvest occurred less frequently and was only possible with harvest strategies that targeted adults when both fecundity and adult survivorship were high. We considered these results in conjunction with current literature on nuisance and invasive species to propose general guidelines for assessing the risks associated with control harvest based on life history characteristics of target populations. Our results suggest that species with high per capita fecundity (over discrete breeding periods), short juvenile stages, and fairly constant survivorship rates are most likely to respond undesirably to harvest. It is difficult to determine the extent to which overcompensation and instability could occur during real-world removal efforts, and more empirical removal studies should be undertaken to evaluate population-level responses to control harvests. Nevertheless, our results identify key issues that have been seldom acknowledged and are potentially generic across taxa. ?? 2009 by the Ecological Society ot America.

Ecological Applications↗

USGS2009

Tamarisk biocontrol in the western United States: Ecological and societal implications

Tamarisk species (genus Tamarix), also commonly known as saltcedar, are among the most successful plant invaders in the western United States. At the same time, tamarisk has been cited as having enormous economic costs. Accordingly, local, state, and federal agencies have undertaken considerable efforts to eradicate this invasive plant and restore riparian habitats to pre-invasion status. Traditional eradication methods, including herbicide treatments, are now considered undesirable, because they are costly and often have unintended negative impacts on native species. A new biological control agent, the saltcedar leaf beetle (Diorhabda elongata), has been released along many watersheds in the western US, to reduce the extent of tamarisk cover in riparian areas. However, the use of this insect as a biological control agent may have unintended ecological, hydrological, and socioeconomic consequences that need to be anticipated by land managers and stakeholders undertaking restoration efforts. Here, we examine the possible ramifications of tamarisk control and offer recommendations to reduce potential negative impacts on valued riparian systems in the western US.

Frontiers in Ecology and the Environment↗