3899761
Wetland characteristics linked to broad-scale patterns in Culiseta melanura abundance and eastern equine encephalitis virus infection
BackgroundEastern equine encephalitis virus (EEEV) is an expanding mosquito-borne threat to humans and domestic animal populations in the northeastern United States. Outbreaks of EEEV are challenging to predict due to spatial and temporal uncertainty in the abundance and viral infection of Cs. melanura, the principal enzootic vector. EEEV activity may be closely linked to wetlands because they provide essential habitat for mosquito vectors and avian reservoir hosts. However, wetlands are not homogeneous and can vary by vegetation, connectivity, size, and inundation patterns. Wetlands may also have different effects on EEEV transmission depending on the assessed spatial scale. We investigated associations between wetland characteristics and Cs. melanura abundance and infection with EEEV at multiple spatial scales in Connecticut, USA.ResultsOur findings indicate that wetland vegetative characteristics have strong associations with Cs. melanura abundance. Deciduous and evergreen forested wetlands were associated with higher Cs. melanura abundance, likely because these wetlands provide suitable subterranean habitat for Cs. melanura development. In contrast, Cs. melanura abundance was negatively associated with emergent and scrub/shrub wetlands, and wetland connectivity to streams. These relationships were generally strongest at broad spatial scales. Additionally, the relationships between wetland characteristics and EEEV infection in Cs. melanura were generally weak. However, Cs. melanura abundance was strongly associated with EEEV infection, suggesting that wetland-associated changes in abundance may be indirectly linked to EEEV infection in Cs. melanura. Finally, we found that wet hydrological conditions during the transmission season and during the fall/winter preceding the transmission season were associated with higher Cs. melanura abundance and EEEV infection, indicating that wet conditions are favorable for EEEV transmission.ConclusionsThese results expand the broad-scale understanding of the effects of wetlands on EEEV transmission and help to reduce the spatial and temporal uncertainty associated with EEEV outbreaks.
39046841
Eastern equine encephalomyelitis virus: epidemiology and evolution of mosquito transmission.
Publisher Summary This chapter focuses on the role of mosquitoes in the enzootic transmission of eastern equine encephalomyelitis (EEE) virus and discusses the historic and epidemiologic knowledge, structure and replication, and transmission cycles of the virus. Studies on mosquito–virus interactions and speculation on the significance of these findings have been summarized in the chapter. Early studies of EEE virus described the disease caused by this virus, identified the virus as an etiological agent, and determined arthropod and vertebrate hosts for enzootic and epidemic transmission. Subsequent studies provided important details on mosquito bionomics, vector–virus interactions, and basic virology. Because EEE virus is easy to work with in the laboratory, the virus has also been used as a model for testing concepts in entomological aspects of arbovirology. Multiple blood-feeding by mosquitoes during a single gonotrophic cycle increases the probability of virus persistence during interepidemic periods and the explosive spread of diseases during epidemics. EEE virus transmission cycles can be used to test the importance of this prediction. Moreover, the techniques that are being developed—histological examination of engorged mosquitoes and alkali metal blood markers in sentinel hosts—have broad application to hematophagous arthropods that transmit a variety of diseases.
26012413
Emergence of Eastern Encephalitis in Massachusetts a
The 20th century emergence in Massachusetts of zoonotic eastern encephalitis was interpreted in terms of recorded environmental change. The main mosquito vector of the infection, Cs. melanura, appears to have been scarce in eastern North America before the 1930s. Its relative scarcity resulted from destruction of the swamps that had been lumbered or drained for farming in the 18th and 19th centuries. When swamps matured once again early in the 1900s, the formation of subsurface pools of water beneath mature trees would have increased the availability of breeding sites for this mosquito. Transmission would have further been enhanced by the simultaneous proliferation of wetland-roosting robins and the extinction of such vagile birds as the passenger pigeon. Although numerous horses were maintained in Massachusetts at the time, no outbreaks of "equine sleeping sickness" came to public notice between the 1830s and the 1930s, when mature trees were scarce and the fauna was most disturbed. The severity of the first major outbreak in 1938 may have been potentiated by the absence of herd-immunity in a rapidly proliferating population of reservoir birds. These considerations suggest that recent landscape and faunal changes caused zoonotic EE to emerge in Massachusetts after waning for a century.
205109173
Eastern equine encephalitis virus--old enemy, new threat.
Over the past decade, we have witnessed a sustained resurgence of eastern equine encephalitis virus activity within long-standing foci in the northeastern United States and northward expansion into regions where the virus was historically rare or previously unknown.
6754629
Eastern Equine Encephalitis Virus in Mosquitoes and Their Role as Bridge Vectors
TOC summary: Virus titers are useful for assessing which mosquito species may transmit virus.
29365525
Epizootiology of eastern equine encephalitis virus in upstate New York, USA. VII. Virus surveillance 1978-85, description of 1983 outbreak, and series conclusions.
Mosquito and arbovirus surveillance activities have been routinely conducted in upstate New York since 1971. This report details the surveillance results during 1978–85. Minimal virus activity was detected in the first 4 yr of concentrated surveillance at Toad Harbor Swamp, Oswego County. In 1983, an outbreak of eastern equine encephalitis (EEE) resulted in one human and nine equine cases. The outbreak was preceded by an epiornitic of Highlands J (HJ) virus in 1982; this was the first evidence of HJ virus activity in the region. Isolations of EEE virus from mosquitoes in 1983 incriminated Culiseta melanura (Coquillett) and Cs. morsitans (Dyar) as epiornitic vectors and Aedes canadensis (Theobald) as an epizootic vector. Mosquito collection data from two endemic foci indicated substantial and significant differences in EEE virus infection rates. The occurrence of HJ virus, the differences in mosquito infection rates, and widespread epizootic disease during a year of low mosquito densities are used to develop a hypothesis on the distribution of multiple endemic foci of EEE virus in upstate New York.
11630608
Field Observations on the Overwintering Ecology of Culiseta melanura in the Northeastern USA
Abstract The overwintering ecology of Culiseta melanura was studied in a seasonally flooded evergreen forest swamp in south central Connecticut in an effort to clarify which larval stages successfully overwinter in the northeastern USA, and to determine the degree to which larval development and/or mortality occur during the winter months. A total of 8,626 immature Cs. melanura were collected weekly for analysis from subterranean crypts and cavities located under the roots of trees from December 13, 2011 to May 31, 2012. Despite the formation of ice on the surface water at the entrance holes to the crypts, water temperatures within the cavities remained above freezing (average  =  1.8°C) throughout the coldest winter months of January and February. A heterogeneous population of 2nd, 3rd, and 4th instars were recovered throughout the winter and early spring in the same relative proportions (30%, 30%, 40%, respectively), with no significant change in their comparative abundance during this period, providing unequivocal evidence that all 3 instars successfully overwinter in the region. Findings further demonstrate that larvae undergo no development during the winter and do not appear to be impacted by any measurable mortality. The cessation of larval diapause and a resumption of development was observed in mid-April and was coincident with a gradual increase in water temperature within the crypts to 9°C, in agreement with a previously calculated developmental thermal minimum of 8.5°C for Cs. melanura. This resulted in a protracted period of pupation that encompassed a minimum of 5 wk, followed by a staggered emergence of adults and an overlap of the residual overwintering population with larvae of the 1st summer generation.
131645225
The Ecology of Atlantic White Cedar Wetlands: A Community Profile
This monograph on the ecology of Atlantic white cedar wetlands is one of a series of U.S. Fish and Wildlife 
Service profiles of important freshwater wetland ecosystems of the United States. The purpose of the profile is to describe the extent, components, functioning, history, and treatment of these wetlands. It is intended to provide a useful reference to relevant scientific information and a synthesis of the available literature. 
 
The world range of Atlantic white cedar (Chamaecyparis thyoides) is limited to a ribbon of freshwater wetlands 
within 200 km of the Atlantic and Gulf coasts of the United States, extending from mid-Maine to mid-Florida and Mississippi. Often in inaccessible sites and difficult to traverse, cedar wetlands contain distinctive suites of plant species. Highly valued as commercial timber since the early days of European colonization of the continent, the cedar and its habitat are rapidly disappearing. 
 
This profile describes the Atlantic white cedar and the bogs and swamps it dominates or codominates throughout its range, discussing interrelationships with other habitats, putative origins and migration patterns, substrate biogeochemistry, associated plant and animal species (with attention to those that are rare, endangered, or threatened regionally or nationally), and impacts of both natural and anthropogenic disturbance. Research needs for each area are outlined. Chapters are devoted to the practices and problems of harvest and management, and to an examination of a large preserve recently acquired by the USFWS, the 
Alligator River National Wildlife Refuge in North Carolina.
490427
CLIMATOLOGICAL CONDITIONS ASSOCIATED WITH OUTBREAKS OF EASTERN ENCEPHALITIS.
Summary
An analysis made of the weather conditions associated with human outbreaks of eastern encephalitis in the United States revealed that the major outbreaks occurred in Massachusetts and New Jersey, and that a weather pattern of excessive rainfall during the summer of the outbreaks and the preceding autumn was consistently associated with the disease outbreaks. The only other state which reported four or more human cases in a single year was Louisiana with ten reported cases in 1947, during which no specific weather pattern was apparent.
Equine outbreaks of eastern encephalitis in Massachusetts and New Jersey coincided with human outbreaks and were, therefore, associated with the same weather pattern. The relationship between the amount of precipitation and the number of equine cases was less consistent in Delaware and Maryland, and only occasional associations were noted between excessive amounts of rainfall and equine outbreaks in Florida, Louisiana, and Texas.
It seems reasonable that weather conditions might be used to predict human and equine outbreaks of eastern encephalitis in the northeastern United States. In the Taunton, Massachusetts, area there would appear to be danger of an eastern encephalitis outbreak during any year when 26 inches or more of rainfall had accumulated during the previous August through October and the current June and July.
In states south of New Jersey, the available data are not adequate to provide a basis for predicting epidemics or epizootics.
86232085
The ecology of climate change and infectious diseases
The projected global increase in the distribution and prevalence of infectious diseases with climate change suggests a pending societal crisis. The subject is increasingly attracting the attention of health professionals and climate-change scientists, particularly with respect to malaria and other vector-transmitted human diseases. The result has been the emergence of a crisis discipline, reminiscent of the early phases of conservation biology. Latitudinal, altitudinal, seasonal, and interannual associations between climate and disease along with historical and experimental evidence suggest that climate, along with many other factors, can affect infectious diseases in a nonlinear fashion. However, although the globe is significantly warmer than it was a century ago, there is little evidence that climate change has already favored infectious diseases. While initial projections suggested dramatic future increases in the geographic range of infectious diseases, recent models predict range shifts in disease distributions, with little net increase in area. Many factors can affect infectious disease, and some may overshadow the effects of climate.
205277378
Spatial scale modulates the strength of ecological processes driving disease distributions
Significance For four decades, ecologists have hypothesized that biotic interactions predominantly control species’ distributions at local scales, whereas abiotic factors operate more at regional scales. Here, we demonstrate that the drivers of three emerging diseases (amphibian chytridiomycosis, West Nile virus, and Lyme disease) in the United States support the predictions of this fundamental hypothesis. Humans are contributing to biodiversity loss, changes in dispersal patterns, and global climate change at an unprecedented rate. Our results highlight that common single-scale analyses can misestimate the impact that humans are having on biodiversity, disease, and the environment. Humans are altering the distribution of species by changing the climate and disrupting biotic interactions and dispersal. A fundamental hypothesis in spatial ecology suggests that these effects are scale dependent; biotic interactions should shape distributions at local scales, whereas climate should dominate at regional scales. If so, common single-scale analyses might misestimate the impacts of anthropogenic modifications on biodiversity and the environment. However, large-scale datasets necessary to test these hypotheses have not been available until recently. Here we conduct a cross-continental, cross-scale (almost five orders of magnitude) analysis of the influence of biotic and abiotic processes and human population density on the distribution of three emerging pathogens: the amphibian chytrid fungus implicated in worldwide amphibian declines and West Nile virus and the bacterium that causes Lyme disease (Borrelia burgdorferi), which are responsible for ongoing human health crises. In all three systems, we show that biotic factors were significant predictors of pathogen distributions in multiple regression models only at local scales (∼102–103 km2), whereas climate and human population density always were significant only at relatively larger, regional scales (usually >104 km2). Spatial autocorrelation analyses revealed that biotic factors were more variable at smaller scales, whereas climatic factors were more variable at larger scales, as is consistent with the prediction that factors should be important at the scales at which they vary the most. Finally, no single scale could detect the importance of all three categories of processes. These results highlight that common single-scale analyses can misrepresent the true impact of anthropogenic modifications on biodiversity and the environment.
87408979
The Bionomics of Culiseta melanura and Culiseta morsitans dyari in Central New York State (Diptera: Culicidae)
Culiseta melanura (Coquillett) were found to overwinter as 4th instars and were trivoltine at this latitude. Logs were preferred resting sites of blood engorged, parous, and gravid females and males. Nullipars were more common in artificial resting boxes. Culiseta morsitans dyari (Theobald) larvae were found mainly with spring Aedes and did not occur after June. Their habitat was less specific than C. melanura and adults preferred resting logs to boxes and did not disperse as rapidly as C. melanura. C. morsitans dyari were univoltine and ♀ were long-lived with the ability to complete at least 3 gonotrophic cycles. In central New York State over-wintering was probably in the egg stage and adults preferred birds as hosts. Adults of both species laid egg rafts and were nocturnal. Parous ♀ were more attracted to light traps and nullipars were more common in resting sites.
207746474
Landscape epidemiology of emerging infectious diseases in natural and human-altered ecosystems.
A central challenge to studying emerging infectious diseases (EIDs) is a landscape dilemma: Our best empirical understanding of disease dynamics occurs at local scales, whereas pathogen invasions and management occur over broad spatial extents. The burgeoning field of landscape epidemiology integrates concepts and approaches from disease ecology with the macroscale lens of landscape ecology, enabling examination of disease across spatiotemporal scales in complex environmental settings. We review the state of the field and describe analytical frontiers that show promise for advancement, focusing on natural and human-altered ecosystems. Concepts fundamental to practicing landscape epidemiology are discussed, including spatial scale, static versus dynamic modeling, spatially implicit versus explicit approaches, selection of ecologically meaningful variables, and inference versus prediction. We highlight studies that have advanced the field by incorporating multiscale analyses, landscape connectivity, and dynamic modeling. Future research directions include understanding disease as a component of interacting ecological disturbances, scaling up the ecological impacts of disease, and examining disease dynamics as a coupled human-natural system.
38818770
Comparative Analysis of Distribution and Abundance of West Nile and Eastern Equine Encephalomyelitis Virus Vectors in Suffolk County, New York, Using Human Population Density and Land Use/Cover Data
Abstract Five years of CDC light trap data from Suffolk County, NY, were analyzed to compare the applicability of human population density (HPD) and land use/cover (LUC) classification systems to describe mosquito abundance and to determine whether certain mosquito species of medical importance tend to be more common in urban (defined by HPD) or residential (defined by LUC) areas. Eleven study sites were categorized as urban or rural using U.S. Census Bureau data and by LUC types using geographic information systems (GISs). Abundance and percent composition of nine mosquito taxa, all known or potential vectors of arboviruses, were analyzed to determine spatial patterns. By HPD definitions, three mosquito species, Aedes canadensis (Theobald), Coquillettidia perturbans (Walker), and Culiseta melanura (Coquillett), differed significantly between habitat types, with higher abundance and percent composition in rural areas. Abundance and percent composition of these three species also increased with freshwater wetland, natural vegetation areas, or a combination when using LUC definitions. Additionally, two species, Ae. canadensis and Cs. melanura, were negatively affected by increased residential area. One species, Aedes vexans (Meigen), had higher percent composition in urban areas. Two medically important taxa, Culex spp. and Aedes triseriatus (Say), were proportionally more prevalent in residential areas by LUC classification, as was Aedes trivittatus (Coquillett). Although HPD classification was readily available and had some predictive value, LUC classification resulted in higher spatial resolution and better ability to develop location specific predictive models.
11109085
North American Wetlands and Mosquito Control
Wetlands are valuable habitats that provide important social, economic, and ecological services such as flood control, water quality improvement, carbon sequestration, pollutant removal, and primary/secondary production export to terrestrial and aquatic food chains. There is disagreement about the need for mosquito control in wetlands and about the techniques utilized for mosquito abatement and their impacts upon wetlands ecosystems. Mosquito control in wetlands is a complex issue influenced by numerous factors, including many hard to quantify elements such as human perceptions, cultural predispositions, and political climate. In spite of considerable progress during the last decades, habitat protection and environmentally sound habitat management still remain inextricably tied to politics and economics. Furthermore, the connections are often complex, and occur at several levels, ranging from local businesses and politicians, to national governments and multinational institutions. Education is the key to lasting wetlands conservation. Integrated mosquito abatement strategies incorporate many approaches and practicable options, as described herein, and need to be well-defined, effective, and ecologically and economically sound for the wetland type and for the mosquito species of concern. The approach will certainly differ in response to disease outbreaks caused by mosquito-vectored pathogens versus quality of life issues caused by nuisance-biting mosquitoes. In this contribution, we provide an overview of the ecological setting and context for mosquito control in wetlands, present pertinent information on wetlands mosquitoes, review the mosquito abatement options available for current wetlands managers and mosquito control professionals, and outline some necessary considerations when devising mosquito control strategies. Although the emphasis is on North American wetlands, most of the material is applicable to wetlands everywhere.
85886313
Drought‐induced mosquito outbreaks in wetlands
Mosquitoes are not only a nuisance, but also vector many important human and animal diseases. Here, in opposition with the dogma that increased precipitation predicts mosquito abundance, we hypothesize that mosquitoes should show population outbreaks after drought years. Specifically, we suggest that in wetlands that never dry (permanent), predators limit mosquito abundance, whereas in wetlands that dry yearly (temporary), competitors that are well adapted to predictable drying, limit mosquito abundance. However, in wetlands that dry only during drought years (semi-permanent), mosquito predators and competitors are eliminated and must recolonize following a drought, and the abundance of wetland mosquitoes can skyrocket. We present supportive evidence for this hypothesis from surveys of natural wetlands and from a controlled mesocosm experiment. We conclude that this framework may provide a reliable way to predict and prepare for year-to-year variation in mosquito abundances at large spatial scales.
84440389
Wetland isolation facilitates larval mosquito density through the reduction of predators
1 Wetlands harbour high biodiversity and offer important ecosystem services, but they are also a habitat for mosquito larvae (Diptera: Culicidae), which are important disease vectors. 2 Isolation among remnant, or newly created wetlands and ponds, and their consequent density in the landscape, is a key factor that can influence a variety of food web processes, including effects on mosquitoes which are important prey to many predators. 3 We assess the impact of habitat isolation on the density of pond‐breeding mosquitoes (several Anopheles and Culex species) both directly and indirectly through the food web. 4 Results from structural equation modelling of survey data shows that larval mosquitoes are denser in ponds that are more isolated from one another, and that this result was primarily driven indirectly by a reduction of larval mosquito predators (e.g. predaceous insects and amphibians). Furthermore, results from a long‐term mesocosm experiment factorially manipulating isolation and predator reduction show that the effect of isolation on mosquito density was eliminated when predators were experimentally reduced. 5 It is concluded that metacommunity processes, both directly and indirectly mediated through predators, can play an important role in the local abundance of wetland breeding mosquitoes and possibly the diseases they spread.
84214740
Increasing isolation reduces predator:prey species richness ratios in aquatic food webs
The number of species that live in a habitat typically declines as that habitat becomes more isolated. However, the influence of habitat isolation on patterns of food web structure, in particular the ratio of predator to prey species richness, is less well understood. We placed aquatic mesocosms at varying distances from ponds that acted as sources of potential colonists; then we examined how isolation affected the ratio of predator:prey species richness in the communities that assembled. In the final sampling, a total of 21 species (12 prey and 9 predators) of insects, crustaceans, and amphibians had colonized the mesocosms. We found that total species richness, as well as the richness of predators and prey, declined with increasing isolation. However, predator richness declined more rapidly than prey richness with increasing isolation, which lead to decreasing predator:prey ratios. This result conflicts with prior demonstrations of invariant predator:prey ratios in freshwater communities.
39721327
Macroinvertebrate patterns along environmental gradients and hydrological connectivity within a regulated river-floodplain
Abstract.Flood and flow pulses are primary factors that regulate macroinvertebrate community structure in river-floodplain ecosystems. In order to assess the impacts of these important hydrological events in a regulated Mediterranean river, bimonthly water and macroinvertebrate samples were collected in 2006 in the Middle Ebro River channel and six floodplain wetlands (NE Spain).We found significant differences among the river sites (permanently connected), two constructed wetlands (groundwater seepage) and three natural oxbow lakes (surface connected at 400, 800 and 1200 m3/s). River sites were dominated by aquatic worms (e.g., Naididae) and showed a high degree of eutrophication. Constructed wetlands provided new habitat for predatory insects (e.g.,Coenagrion scitulum and Trithemis annulata) that benefited from the absence of fish. Natural oxbow lakes were dominated by crustaceans (e.g., Atyaephyra desmarestii, Procambarus clarkii) and were highly overlapped in Correspondence Analysis. Canonical Correspondence Analysis, coupled with variance partitioning, showed that hydrological connectivity accounted for 28% of the variability in the invertebrate community, followed by physicochemical (10%) and trophic (7%) factors. Differences in frequency and duration of flood pulses in natural oxbow lakes were not enough to generate distinctive macroinvertebrate assemblages in the different wetlands. Analysis of variance showed that richness and total abundance increased with hydrological connectivity, while diversity showed a rather unimodal distribution. Generalized Additive Models indicated that among the measured environmental variables, nitrate concentration strongly affected the composition, abundance and diversity of aquatic communities. Our data indicate that increasing the diversity of water body types in degraded floodplains enhances biodiversity and aids in the functional and ecological recovery of the riverine landscape.
9028374
Host selection by Culex pipiens mosquitoes and West Nile virus amplification.
Recent field studies have suggested that the dynamics of West Nile virus (WNV) transmission are influenced strongly by a few key super spreader bird species that function both as primary blood hosts of the vector mosquitoes (in particular Culex pipiens) and as reservoir-competent virus hosts. It has been hypothesized that human cases result from a shift in mosquito feeding from these key bird species to humans after abundance of the key birds species decreases. To test this paradigm, we performed a mosquito blood meal analysis integrating host-feeding patterns of Cx. pipiens, the principal vector of WNV in the eastern United States north of the latitude 36 degrees N and other mosquito species with robust measures of host availability, to determine host selection in a WNV-endemic area of suburban Chicago, Illinois, during 2005-2007. Results showed that Cx. pipiens fed predominantly (83%) on birds with a high diversity of species used as hosts (25 species). American robins (Turdus migratorius) were marginally overused and several species were underused on the basis of relative abundance measures, including the common grackle (Quiscalus quiscula), house sparrow (Passer domesticus), and European starling (Sturnus vulgaris). Culex pipiens also fed substantially on mammals (19%; 7 species with humans representing 16%). West Nile virus transmission intensified in July of both years at times when American robins were heavily fed upon, and then decreased when robin abundance decreased, after which other birds species were selected as hosts. There was no shift in feeding from birds to mammals coincident with emergence of human cases. Rather, bird feeding predominated when the onset of the human cases occurred. Measures of host abundance and competence and Cx. pipiens feeding preference were combined to estimate the amplification fractions of the different bird species. Predictions were that approximately 66% of WNV-infectious Cx. pipiens became infected from feeding on just a few species of birds, including American robins (35%), blue jays (17%, Cyanocitta cristata), and house finches (15%, Carpodacus mexicanus).
6646718
A multi-year study of mosquito feeding patterns on avian hosts in a southeastern focus of eastern equine encephalitis virus.
Eastern equine encephalitis virus (EEEV) is a mosquito-borne pathogen that cycles in birds but also causes severe disease in humans and horses. We examined patterns of avian host use by vectors of EEEV in Alabama from 2001 to 2009 using blood-meal analysis of field-collected mosquitoes and avian abundance surveys. The northern cardinal (Cardinalis cardinalis) was the only preferred host (fed on significantly more than expected based on abundance) of Culiseta melanura, the enzootic vector of EEEV. Preferred hosts of Culex erraticus, a putative bridge vector of EEEV, were American robin (Turdus migratorius), Carolina chickadee (Poecile carolinensis), barred owl (Strix varia), and northern mockingbird (Mimus polyglottis). Our results provide insight into the relationships between vectors of EEEV and their avian hosts in the Southeast and suggest that the northern cardinal may be important in the ecology of EEEV in this region.
16502404
The roles of mosquito and bird communities on the prevalence of West Nile virus in urban wetland and residential habitats
This study investigated the impacts of urban wetlands and their adjacent residential environments on the transmission dynamics of West Nile virus (WNV) within the state of New Jersey (USA). A working hypothesis was that urban wetlands decrease the local prevalence of WNV through the dilution effect from increased bird diversity, and through relative reductions in the numbers of competent avian host and mosquito species commonly associated with WNV. Surveys of mosquito and bird communities were undertaken at six urban wetlands and their adjacent residential environments over two seasons (2009, 2010). The community compositions of both avian and mosquito species differed significantly across habitats, and over relatively short geographical distances. Residential areas contained significantly higher proportions of WNV-competent mosquito species (31.25 ± 5.3 %; e.g. Culex pipiens and Culex restuans), and WNV-competent avian host species (62.8 ± 2.3 %, e.g. House Sparrow and American Robin) when compared to adjacent urban wetlands (13.5 ± 2.1 %; 35.4 ± 2.1 % respectively). Correspondingly, WNV infection rates within local Culex spp. populations indicate that WNV was more prevalent within residential areas (28.53/1000) compared to wetlands (16.77/1000). Large urban wetlands (>100 ha) produced significantly lower weekly WNV infection rates in local Culex spp. (6.67 ± 2.84/1000) compared to small (<15 ha) wetlands (22.57 ± 6.23/1000). Avian species richness was also influenced by patch size. Large urban wetlands contained significantly more species than small wetland patches. These results confirm that the community compositions of mosquito and avian hosts are important drivers in WNV infections, and that the ecological conditions that favor transmission are more strongly associated with urban residential environments than with adjacent urban wetlands.
38193068
Managing Wetland Habitats for Waterbirds: An International Perspective
The loss and degradation of wetlands worldwide has adversely affected waterbirds, which depend on wetland habitats. Many studies have indicated that effectively managed wetlands can provide alternative or complementary habitats for waterbirds and mitigate the adverse effects of wetland loss and degradation. We review the studies on the habitat variables affecting use of wetlands by waterbirds, and we suggest how wetlands can be managed to provide waterbird habitat. These habitat variables include water depth, water level fluctuation, vegetation, salinity, topography, food type, food accessibility, wetland size, and wetland connectivity. Overall, the practice of wetland management requires integrated knowledge related to the entire wetland ecosystem, and ecosystem-based approach is needed to improve the habitat quality of managed wetlands with considering multiple spatial scales, temporal variability, and trade-off among diverse habitat requirements of different waterbirds. Several priorities for future research and management are also suggested in this paper.
29368507
Drought-Induced Amplification and Epidemic Transmission of West Nile Virus in Southern Florida
Abstract We show that the spatial-temporal variability of human West Nile (WN) cases and the transmission of West Nile virus (WNV) to sentinel chickens are associated with the spatial-temporal variability of drought and wetting in southern Florida. Land surface wetness conditions at 52 sites in 31 counties in southern Florida for 2001–2003 were simulated and compared with the occurrence of human WN cases and the transmission of WNV to sentinel chickens within these counties. Both WNV transmission to sentinel chickens and the occurrence of human WN cases were associated with drought 2–6 mo prior and land surface wetting 0.5–1.5 mo prior. These dynamics are similar to the amplification and transmission patterns found in southern Florida for the closely related St. Louis encephalitis virus. Drought brings avian hosts and vector mosquitoes into close contact and facilitates the epizootic cycling and amplification of the arboviruses within these populations. Southern Florida has not recorded a severe, widespread drought since the introduction of WNV into the state in 2001. Our results indicate that widespread drought in the spring followed by wetting during summer greatly increase the probability of a WNV epidemic in southern Florida.
40321999
The spatial-temporal distribution of drought, wetting, and human cases of St. Louis encephalitis in southcentral Florida.
Using a dynamic hydrology model, we simulated land surface wetness conditions at 42 sites in 28 counties in southcentral Florida from 1990 to 1998 and compared these simulations with the incidence of human cases of St. Louis encephalitis (SLE) within these counties. Within counties, drought four months prior and wetting one-half month prior were significantly associated with human cases of SLE. Simulated land surface wetness conditions resolved transmission loci in both space and time, and May drought was significantly associated with the subsequent occurrence of human SLE cases. These findings are consistent with previous results associating simulated land surface wetness conditions with the transmission of SLE virus as measured in sentinel chickens, and support our working hypothesis that springtime drought facilitates SLE virus amplification in mosquito and wild bird populations.
11469551
St. Louis Encephalitis Virus in Wild Birds During the 1990 South Florida Epidemic: The Importance of Drought, Wetting Conditions, and the Emergence of Culex nigripalpus (Diptera: Culicidae) to Arboviral Amplification and Transmission
Abstract We analyzed the prevalence of hemagglutination inhibition (HI) antibodies to St. Louis encephalitis (SLE) virus in wild birds during the 1990 SLE epidemic in Indian River County. The initial presence of SLE HI antibody was associated significantly with modeled drought 15 wk prior, wetting conditions 1 wk prior, and the emergence of the Florida SLE virus vector, Culex nigripalpus, 5 wk prior. Our findings indicated that three factors conspired to create the 1990 epidemic: (1) a large population of susceptible wild birds; (2) severe springtime drought, which facilitated amplification of the SLE virus among the Cx. nigripalpus and a portion of the wild bird population; and (3) continued rainfall and wetting of the land surface in the summer and early fall, which sustained a large, host-seeking Cx. nigripalpus population. The continued biting and reproductive activity of Cx. nigripalpus maintained epizootic transmission throughout the summer and early fall in Indian River County. The high level of SLE virus amplification resulted in spillover transmission to humans. We hypothesize that without the continued reproductive activity of the vector mosquito, brought about by excessive summer and fall wetness, the unprecedented SLE virus amplification and consequent transmission to humans would not have been realized in 1990.
14643110
Fine-scale wetland features mediate vector and climate-dependent macroscale patterns in human West Nile virus incidence
AbstractContextMosquito-borne diseases in the United States are notorious for their seemingly erratic temporal and spatial outbreak patterns in humans. Identifying linkages between fine-scale phenomenon and macroscale outbreak patterns can improve the understanding of these complex socio–ecological systems.ObjectivesUsing West Nile virus (WNV) as a model system, we examine whether fine-scale wetland characteristics—wetland size, connectivity, and inundation regime—have an important effect on macroscale human disease outbreak in the northeastern and midwestern United States.MethodsWe take a spatially explicit GIS-based approach, derive new macroscale wetland metrics based on fine-scale wetland characteristics, and use county-level annual human WNV incidence data over 11 years to evaluate linkages between the fine and macroscales (1.6 million km2).ResultsIn regions dominated by the Culex tarsalis WNV vector, U.S. counties with a small average wetland size had more than 100 % higher human WNV incidence than counties with a large average wetland size. In regions dominated by the Cx. pipiens and Cx. restuans vectors, a low proportional area of connected wetland was associated with at least 50 % higher human WNV incidence than a high proportional area of connected wetland. Finally, Cx. tarsalis-dominated counties with a high proportional area of semi-permanent wetland that were experiencing drought conditions had over 300 % higher annual WNV incidence than drought-affected counties with a low proportional area of semi-permanent wetland.ConclusionsOur results suggest that phenomena occurring at the individual wetland scale may aggregate to influence macroscale human WNV outbreak patterns and may be mediated by the interplay of other factors such as vector species-specific traits and climate.

11032695
Building a multi-scaled geospatial temporal ecology database from disparate data sources: fostering open science and data reuse
Although there are considerable site-based data for individual or groups of ecosystems, these datasets are widely scattered, have different data formats and conventions, and often have limited accessibility. At the broader scale, national datasets exist for a large number of geospatial features of land, water, and air that are needed to fully understand variation among these ecosystems. However, such datasets originate from different sources and have different spatial and temporal resolutions. By taking an open-science perspective and by combining site-based ecosystem datasets and national geospatial datasets, science gains the ability to ask important research questions related to grand environmental challenges that operate at broad scales. Documentation of such complicated database integration efforts, through peer-reviewed papers, is recommended to foster reproducibility and future use of the integrated database. Here, we describe the major steps, challenges, and considerations in building an integrated database of lake ecosystems, called LAGOS (LAke multi-scaled GeOSpatial and temporal database), that was developed at the sub-continental study extent of 17 US states (1,800,000 km2). LAGOS includes two modules: LAGOSGEO, with geospatial data on every lake with surface area larger than 4 ha in the study extent (~50,000 lakes), including climate, atmospheric deposition, land use/cover, hydrology, geology, and topography measured across a range of spatial and temporal extents; and LAGOSLIMNO, with lake water quality data compiled from ~100 individual datasets for a subset of lakes in the study extent (~10,000 lakes). Procedures for the integration of datasets included: creating a flexible database design; authoring and integrating metadata; documenting data provenance; quantifying spatial measures of geographic data; quality-controlling integrated and derived data; and extensively documenting the database. Our procedures make a large, complex, and integrated database reproducible and extensible, allowing users to ask new research questions with the existing database or through the addition of new data. The largest challenge of this task was the heterogeneity of the data, formats, and metadata. Many steps of data integration need manual input from experts in diverse fields, requiring close collaboration.
34719698
LAGOS-NE: a multi-scaled geospatial and temporal database of lake ecological context and water quality for thousands of US lakes
Abstract Understanding the factors that affect water quality and the ecological services provided by freshwater ecosystems is an urgent global environmental issue. Predicting how water quality will respond to global changes not only requires water quality data, but also information about the ecological context of individual water bodies across broad spatial extents. Because lake water quality is usually sampled in limited geographic regions, often for limited time periods, assessing the environmental controls of water quality requires compilation of many data sets across broad regions and across time into an integrated database. LAGOS-NE accomplishes this goal for lakes in the northeastern-most 17 US states. LAGOS-NE contains data for 51 101 lakes and reservoirs larger than 4 ha in 17 lake-rich US states. The database includes 3 data modules for: lake location and physical characteristics for all lakes; ecological context (i.e., the land use, geologic, climatic, and hydrologic setting of lakes) for all lakes; and in situ measurements of lake water quality for a subset of the lakes from the past 3 decades for approximately 2600–12 000 lakes depending on the variable. The database contains approximately 150 000 measures of total phosphorus, 200 000 measures of chlorophyll, and 900 000 measures of Secchi depth. The water quality data were compiled from 87 lake water quality data sets from federal, state, tribal, and non-profit agencies, university researchers, and citizen scientists. This database is one of the largest and most comprehensive databases of its type because it includes both in situ measurements and ecological context data. Because ecological context can be used to study a variety of other questions about lakes, streams, and wetlands, this database can also be used as the foundation for other studies of freshwaters at broad spatial and ecological scales.
84976271
Identifying appropriate spatial scales of predictors in species distribution models with the random forest algorithm
Summary 
 
 
Including predictors in species distribution models at inappropriate spatial scales can decrease the variance explained, add residual spatial autocorrelation (RSA) and lead to the wrong conclusions. Some studies have measured predictors within different buffer sizes (scales) around sample locations, regressed each predictor against the response at each scale and selected the scale with the best model fit as the appropriate scale for this predictor. However, a predictor can influence a species at several scales or show several scales with good model fit due to a bias caused by RSA. This makes the evaluation of all scales with good model fit necessary. With potentially several scales per predictor and multiple predictors to evaluate, the number of predictors can be large relative to the number of data points, potentially impeding variable selection with traditional statistical techniques, such as logistic regression. 
We trialled a variable selection process using the random forest algorithm, which allows the simultaneous evaluation of several scales of multiple predictors. Using simulated responses, we compared the performance of models resulting from this approach with models using the known predictors at arbitrary and at the known spatial scales. We also apply the proposed approach to a real data set of curlew (Numenius arquata). 
AIC, AUC and Naglekerke's pseudo R2 of the models resulting from the proposed variable selection were often very similar to the models with the known predictors at known spatial scales. Only two of nine models required the addition of spatial eigenvectors to account for RSA. Arbitrary scale models always required the addition of spatial eigenvectors. 75% (50–100%) of the known predictors were selected at scales similar to the known scale (within 3 km). In the curlew model, predictors at large, medium and small spatial scales were selected, suggesting that for appropriate landscape-scale models multiple scales need to be evaluated. 
The proposed approach selected several of the correct predictors at appropriate spatial scales out of 544 possible predictors. Thus, it facilitates the evaluation of multiple spatial scales of multiple predictors against each other in landscape-scale models.
118737182
Generalized Additive Models: An Introduction with R
LINEAR MODELS A simple linear model Linear models in general The theory of linear models The geometry of linear modelling Practical linear models Practical modelling with factors General linear model specification in R Further linear modelling theory Exercises GENERALIZED LINEAR MODELS The theory of GLMs Geometry of GLMs GLMs with R Likelihood Exercises INTRODUCING GAMS Introduction Univariate smooth functions Additive models Generalized additive models Summary Exercises SOME GAM THEORY Smoothing bases Setting up GAMs as penalized GLMs Justifying P-IRLS Degrees of freedom and residual variance estimation Smoothing Parameter Estimation Criteria Numerical GCV/UBRE: performance iteration Numerical GCV/UBRE optimization by outer iteration Distributional results Confidence interval performance Further GAM theory Other approaches to GAMs Exercises GAMs IN PRACTICE: mgcv Cherry trees again Brain imaging example Air pollution in Chicago example Mackerel egg survey example Portuguese larks example Other packages Exercises MIXED MODELS and GAMMs Mixed models for balanced data Linear mixed models in general Linear mixed models in R Generalized linear mixed models GLMMs with R Generalized additive mixed models GAMMs with R Exercises APPENDICES A Some matrix algebra B Solutions to exercises Bibliography Index
123069570
Improving Forecast of Binary Rare Events Data: A GAM-Based Approach
This paper develops a method for modelling binary response data in a regression model with highly unbalanced class sizes. When the class sizes are highly unbalanced and the minority class represents a rare event, conventional regression analysis, i.e. logistic regression models, could underestimate the probability of the rare event. To overcome this drawback, we introduce a flexible skewed link function based on the quantile function of the generalized extreme value (GEV) distribution in a generalized additive model (GAM). The proposed model is known as generalized extreme value additive (GEVA) regression model, and a modified version of the local scoring algorithm is suggested to estimate it. We apply the proposed model to a dataset on Italian small and medium enterprises (SMEs) to estimate the default probability of SMEs. Our proposal performs better than the logistic (linear or additive) model in terms of predictive accuracy.
14982444
Comparing Models for Early Warning Systems of Neglected Tropical Diseases
Background Early warning systems (EWS) are management tools to predict the occurrence of epidemics of infectious diseases. While climate-based EWS have been developed for malaria, no standard protocol to evaluate and compare EWS has been proposed. Additionally, there are several neglected tropical diseases whose transmission is sensitive to environmental conditions, for which no EWS have been proposed, though they represent a large burden for the affected populations. Methodology/Principal Findings In the present paper, an overview of the available linear and non-linear tools to predict seasonal time series of diseases is presented. Also, a general methodology to compare and evaluate models for prediction is presented and illustrated using American cutaneous leishmaniasis, a neglected tropical disease, as an example. The comparison of the different models using the predictive R 2 for forecasts of “out-of-fit” data (data that has not been used to fit the models) shows that for the several linear and non-linear models tested, the best results were obtained for seasonal autoregressive (SAR) models that incorporate climatic covariates. An additional bootstrapping experiment shows that the relationship of the disease time series with the climatic covariates is strong and consistent for the SAR modeling approach. While the autoregressive part of the model is not significant, the exogenous forcing due to climate is always statistically significant. Prediction accuracy can vary from 50% to over 80% for disease burden at time scales of one year or shorter. Conclusions/Significance This study illustrates a protocol for the development of EWS that includes three main steps: (i) the fitting of different models using several methodologies, (ii) the comparison of models based on the predictability of “out-of-fit” data, and (iii) the assessment of the robustness of the relationship between the disease and the variables in the model selected as best with an objective criterion.
32602441
Culiseta melanura (Diptera: Culicidae): population structure and nectar feeding in a freshwater swamp and surrounding areas in southeastern Massachusetts, USA.
The population structure and nectar feeding patterns of the mosquito Culiseta melanura were studied in and around a freshwater swamp in the EEE virus enzootic areas of southeastern Massachusetts, USA. During the summer of 1978, resting boxes were used to collect 12,994 female Cs. melanura , 1747 of which were dissected for parity and tested for the presence of plant nectar by the anthrone test for fructose. Large numbers of parous and nulliparous females were present at the perimeter of the swamp habitats and in the upland areas up to 4.8 km from the swamps. Population density fluctuations and seasonal parity rates suggested 4 generations or emergences over the course of the season. Population age structures varied in the 2 habitat types. Blood-engorged and gravid females were more prevalent at the swamp perimeter and nulliparous females were more prevalent outside the swamp. Parous females were equally prevalent in both habitats. Parity rate averaged 23.7% for the season, peaked in mid-summer at 40–45%, and was used to calculate a daily survival probability ranging from 0.749 to 0.814 during the study. Nectar feeding at the swamp perimeter differed between population components; parous females were positive for nectar more frequently than nulliparous females, and both were positive more frequently than gravid females. Nectar feeding outside the swamp did not vary between population components. Overall, the percentage of mosquitoes positive for nectar was higher at the perimeter than outside the swamp. Gravid females contained nectar throughout the egg maturation process. Results are discussed with reference to population dispersal, behavior of mosquitoes in various physiological states, and the EEE virus cycle.
7251271
Mark-recapture studies on the Culiseta (Diptera: Culicidae) vectors of eastern equine encephalitis virus.
Natural populations of Culiseta melanura (Coquillett) and Cs. morsitans (Theobald) were marked and released at three sites associated with the Toad Harbor-Big Bay Swamp eastern equine encephalitis (EEE) virus focus in central New York. Collections of Culiseta from surveillance sites within 12.8 km of the release sites were screened for marked specimens. A total of 172 marked specimens were recaptured. The majority of recaptured mosquitoes were collected at sites associated with the swamp complex, but some were collected at seven of the eight recapture sites, up to 9.8 km from a release site. The distances traveled by 103 recaptured individuals were used to calculate the mean distance traveled and flight ranges for sexes and cohorts of both species. The mean distance traveled for females that were marked and released from resting shelters was 4 km for Cs. melanura and 5 km for Cs. morsitans. The mean distance traveled for females marked and released from a CDC + CO2 light trap was 9 km and 8 km for Cs. melanura and Cs. morsitans, respectively. The flight ranges of these species overlap the EEE epizoötic zone, and the results of these studies support the hypothesis that these species are involved in the transfer of EEE virus from swamp to upland habitats.
83193123
Avian Pests. (Book Reviews: Granivorous Birds in Ecosystems. Their Evolution, Populations, Energetics, Adaptations, Impact and Control)
List of contributors Preface J. B. Cragg 1. Introduction S. C. Kendeigh and J. Pinowski 2. Variation and evolution in a granivorous bird: the house sparrow R. F. Johnston and W. J. Klitz 3. Population dynamics M. I. Dyer, J. Pinowski and B. Pinowska 4. Biomass and production rates J. Pinowska and A. Myrcha 5. Avian energetics S. C. Kendeigh, V. R. Dol'nik and V. M. Gavrilov 6. Assessing the potential impact of granivorous birds in ecosystems J. A. Wiens and M. I. Dyer 7. Management of pest situations M. I. Dyer and P. Ward 8. Adaptive correlates of granivory in birds J. A. Wiens and R. F. Johnston 9. Epilogue S. C. Kendeigh, J. A. Wiens and J. Pinowski References Index.
84694124
Scale of Investigation and the Detection of Competition: An Example from the House Sparrow and House Finch Introductions in North America
I present an example that illustrates an evaluation of interspecific competition by combining investigations conducted on different scales. Results from investigations on different scales are interpreted with an assessment of the scales on which the competitors perceive habitat and each other. Interference competition between the introduced house sparrow (Passer domesticus) and native house finch (Carpodacus mexicanus) observed at backyard nest boxes for 4 yr in the western United States may have resulted in habitat segregation on a larger scale along a rural-urban habitat gradient. Competition may be occurring in the eastern states since the introduction of C. mexicanus in 1940. Christmas Bird Count data were examined for patterns in species abundance predicted by competition theory, using three scales of investigation: local (area 24 km in diameter), regional (area 250 km in diameter), and continental (between areas of sympatry and allopatry). The major findings suggest that competition has not influenced patterns of changes in the abundances of the competitors on a local scale in urban and rural habitats in the eastern United States or on a regional scale in the eastern and western United States. On a continental scale, the presence of C. mexicanus may have accelerated widespread declines in the density of P. domesticus in areas of sympatry across the United States, possibly because of the energetic demands of interference competition. The dissimilar behavior and foraging strategies of the competitors may permit coexistence in all habitats, such that the niche of P. domesticus is included in the niche of C. mexicanus. Differences in the perception of habitat by the competitors may preclude the development of habitat segregation along a rural-urban habitat gradient. A multi-scale approach to evaluating interspecific competition suggests that investigations on any single scale (e.g., a field experiment) may overemphasize or miss the importance of competition.
86222012
Species-Specific Survival and Relative Habitat Use in an Urban Landscape During the Postfledging Period
ABSTRACT. In an urban landscape, population viability may require successful movement of recently fledged birds between habitat patches, yet postfledging movements are rarely studied. We used radiotelemetry to track 26 American Robin (Turdus migratorius), 15 Swainson's Thrush (Catharus ustulatus), 46 Spotted Towhee (Pipilo maculatus), and 35 Song Sparrow (Melospiza melodia) fledglings across the urban gradient of the Seattle metropolis, to document the relative use of specific features of the built and forested environment and to correlate land-cover metrics with survival during the postfledging period. Survival of postfledging birds, other than American Robins, was high, and the effects of land cover on survival were limited. Across species, we observed lower survival in forested areas than in the suburban lands around them, but this may have been a function of fledgling age. Once juvenile birds became independent, they often moved into suburbs without increased risk of death. We found little consistency in relative habitat use within species, with the exception of American Robins, which used suburban residential areas more than forested areas. However, resource use by the other species was context-specific: (1) use of residential areas by Song Sparrows was highest where this habitat was least common, (2) use of forested areas by Spotted Towhees decreased with increasing level of urbanization, and (3) use of heavy-medium urban areas by Swainson's Thrush decreased with increasing abundance of roads.
85987890
Food as a limit on breeding birds: a life-history perspective
Food limitation is an important issue in ecology because it can influence life history traits, population sizes, and community structure (through effects of competition). Work at the level of populations and communities has led to arguments that food limitation and competition are more important in winter than during the breeding season (e.g. 1, 2, 7, 8, 83, 85, 211, 234). In fact, it is commonly argued that food is superabundant during the breeding season (7, 8, 161, 213, 246, 250, 251, 308-311). However, such arguments are based on indirect rather than direct evidence of the effects of food on reproduction and survival (fitness) (149). Direct evidence for food limitation and competition in winter exists when survival is affected, and some experimental evidence suggests such effects (e.g. 75, 113, 122, 132). However, if current or future reproductive success is limited by food, then food limitation will also exist during the breeding season. Reproductive ecologists historically have argued that food limits reproductive success (e.g. 13, 297). Yet, even this school has included recent arguments against food limitation. For instance, Ettinger & King (77) think that perching time of birds commonly reflects loafing time because birds set their clutch and brood sizes based on years and periods of stringent (low food) conditions. However, perching time may not reflect loafing but rather an important time commitment to reproductive success (T. Martin, unpublished ms.) Thus, the status of food limitation in breeding birds is not clear. Here, I review evidence for food limitation in the context of life history theory because it provides a fundamental framework from which to interpret
16031188
Antecedent Avian Immunity Limits Tangential Transmission of West Nile Virus to Humans
Background West Nile virus (WNV) is a mosquito-borne flavivirus maintained and amplified among birds and tangentially transmitted to humans and horses which may develop terminal neuroinvasive disease. Outbreaks typically have a three-year pattern of silent introduction, rapid amplification and subsidence, followed by intermittent recrudescence. Our hypothesis that amplification to outbreak levels is contingent upon antecedent seroprevalence within maintenance host populations was tested by tracking WNV transmission in Los Angeles, California from 2003 through 2011. Methods Prevalence of antibodies against WNV was monitored weekly in House Finches and House Sparrows. Tangential or spillover transmission was measured by seroconversions in sentinel chickens and by the number of West Nile neuroinvasive disease (WNND) cases reported to the Los Angeles County Department of Public Health. Results Elevated seroprevalence in these avian populations was associated with the subsidence of outbreaks and in the antecedent dampening of amplification during succeeding years. Dilution of seroprevalence by recruitment resulted in the progressive loss of herd immunity following the 2004 outbreak, leading to recrudescence during 2008 and 2011. WNV appeared to be a significant cause of death in these avian species, because the survivorship of antibody positive birds significantly exceeded that of antibody negative birds. Cross-correlation analysis showed that seroprevalence was negatively correlated prior to the onset of human cases and then positively correlated, peaking at 4–6 weeks after the onset of tangential transmission. Antecedent seroprevalence during winter (Jan – Mar) was negatively correlated with the number of WNND cases during the succeeding summer (Jul–Sep). Conclusions Herd immunity levels within after hatching year avian maintenance host populations <10% during the antecedent late winter and spring period were followed on three occasions by outbreaks of WNND cases during the succeeding summer. Because mosquitoes feed almost exclusively on these avian species, amplification was directly related to the availability of receptive non-immune hosts.
88002295
REPRODUCTIVE BIOLOGY OF SHRUBSTEPPE PASSERINE BIRDS: GEOGRAPHICAL AND TEMPORAL VARIATION IN CLUTCH SIZE, BROOD SIZE, AND FLEDGING SUCCESS'
We investigated geographical and temporal variation in clutch size, brood size, and fledging success in three common passerine species in shrubsteppe habitats of the northern Great Basin of western North America. Over a 2-year period we surveyed three vegetationally similar sites spanning a latitudinal gradient of 650 km (the geographical component), one of which we sampled for five consecutive years (the temporal component). Clutch sizes of Sage (Amphispiza belli) and Brewer's (Spizella breweri) sparrows did not differ significantly among sites, but brood sizes and (for Brewer's Sparrow) fledging success did. These geographical differences were associated with site-specific variation in nest-pre- dation rates and were attributed to differences in the abundances of snakes. Nests at a site in central Oregon that lacked snakes suffered virtually no predation during the 2-year geo- graphical sampling, whereas nests in southeastern Washington and northern Nevada suffered significantly higher rates (40% and 93%, respectively). During the 5-year temporal sampling at the central Oregon site, all measured reproductive parameters of Sage and Brewer's sparrows and clutch size in Sage Thrashers (Oreoscoptes montanus) varied significantly. Although the region experienced extremes of precipitation during this period, in Sage Sparrows only brood size was significantly correlated with rainfall during the previous winter. The principal source of variation in Sage Sparrow final repro- ductive success was predation, which peaked during an outbreak of Townsend's ground squirrels (Spermophilus townsendi) in 1979. This ground squirrel irruption appeared to be triggered by a pattern of a drought year followed by two relatively wet years, beginning in winter 1976-1977. Although Brewer's Sparrows also experienced considerable predation pressure in 1979, clutch size, brood size, and fledging success were significantly correlated with winter precipitation. No component of Sage Thrasher reproduction was associated with climatic variation. The relationship between avian reproductive success and precipitation in arid regions is more complex than the traditional view of desert birds responding directly to increased primary and secondary productivity; such relationships are indirectly influenced by the effects of rainfall on predator populations, and are further complicated by time lags (up to 2 years) in predator response.
82844481
Climate Influences on avian population dynamics
Publisher Summary This chapter reviews studies that have analyzed the effects of local weather and large-scale climate phenomenon on fluctuations in the size of bird populations. Population size depends upon birth rates and death rates and how these interact with density. The variation in these relationships is also important. By understanding how these interact to affect variation in population size, one can examines how climate change may affect the future fluctuations of bird populations. There are three major issues to consider in understanding how climate change may result in changes in population size: whether the climate responses are density dependent or density independent; whether climate change largely affects the reproductive success or the survival; and whether climate change primarily affects the mean values or the variability. The chapter outlines a general theoretical framework based on Lande et al. for analyzing avian population dynamics and describes how an expected change in climate may affect avian population dynamics and thus help resolve the three issues. Modeling and estimating the effects of the density dependence as well as changes in the mean and variance of the relevant climate variables have been discussed.
83058520
Weather-dependent survival: implications of climate change for passerine population processes
Understanding demographic processes will be essential to construct robust models of population responses to climate change. We show that survival is related to the strength of the North Atlantic Oscillation in five out of ten British resident passerine species, and explore the importance of biologically more specific variables (duration of winter frosts and snow periods; occurrence of cold, wet days; spring temperature; and summer drought). The most important variables differed between species in relation to differences in foraging strategy. In almost all cases, first-year survival was influenced by weather more than was the survival of adult birds. Particularly vulnerable species, such as the Wren Troglodytes troglodytes, may exhibit a 25% reduction in juvenile survival rates due to adverse weather within the range experienced in the last 30 years; variation in survival by 10% or more is commonplace in most species. Thus, climate influences on food availability may provide the mechanism by which populations will alter under changed climatic conditions, though the presence of density dependence may reduce the impact of this on long-term population trajectories.
3562581
Rainfall during parental care reduces reproductive and survival components of fitness in a passerine bird
Adverse weather conditions during parental care may have direct consequences for offspring production, but longer-term effects on juvenile and parental survival are less well known. We used long-term data on reproductive output, recruitment, and parental survival in northern wheatears (Oenanthe oenanthe) to investigate the effects of rainfall during parental care on fledging success, recruitment success (juvenile survival), and parental survival, and how these effects related to nestling age, breeding time, habitat quality, and parental nest visitation rates. While accounting for effects of temperature, fledging success was negatively related to rainfall (days > 10 mm) in the second half of the nestling period, with the magnitude of this effect being greater for breeding attempts early in the season. Recruitment success was, however, more sensitive to the number of rain days in the first half of the nestling period. Rainfall effects on parental survival differed between the sexes; males were more sensitive to rain during the nestling period than females. We demonstrate a probable mechanism driving the rainfall effects on reproductive output: Parental nest visitation rates decline with increasing amounts of daily rainfall, with this effect becoming stronger after consecutive rain days. Our study shows that rain during the nestling stage not only relates to fledging success but also has longer-term effects on recruitment and subsequent parental survival. Thus, if we want to understand or predict population responses to future climate change, we need to consider the potential impacts of changing rainfall patterns in addition to temperature, and how these will affect target species' vital rates.
128681158
Accuracy assessment of NLCD 2006 land cover and impervious surface
Abstract Release of NLCD 2006 provides the first wall-to-wall land-cover change database for the conterminous United States from Landsat Thematic Mapper (TM) data. Accuracy assessment of NLCD 2006 focused on four primary products: 2001 land cover, 2006 land cover, land-cover change between 2001 and 2006, and impervious surface change between 2001 and 2006. The accuracy assessment was conducted by selecting a stratified random sample of pixels with the reference classification interpreted from multi-temporal high resolution digital imagery. The NLCD Level II (16 classes) overall accuracies for the 2001 and 2006 land cover were 79% and 78%, respectively, with Level II user's accuracies exceeding 80% for water, high density urban, all upland forest classes, shrubland, and cropland for both dates. Level I (8 classes) accuracies were 85% for NLCD 2001 and 84% for NLCD 2006. The high overall and user's accuracies for the individual dates translated into high user's accuracies for the 2001–2006 change reporting themes water gain and loss, forest loss, urban gain, and the no-change reporting themes for water, urban, forest, and agriculture. The main factor limiting higher accuracies for the change reporting themes appeared to be difficulty in distinguishing the context of grass. We discuss the need for more research on land-cover change accuracy assessment.