Local Gradients of Cowbird Abundance and Parasitism Relative to Livestock Grazing in a Western Landscape

Abstract: We studied local patterns of Brown-headed Cowbird ( Molothrus ater ) abundance, parasitism rates, and nest success of a common host, the Plumbeous Vireo ( Vireo plumbeus ), in relation to the distribution of livestock grazing in an undeveloped region of northeastern New Mexico, 1992–1997. We predicted that both cowbird abundance and parasitism rates of vireo nests would decrease with increasing distance from active livestock grazing, and that the nesting success of vireos would increase. We measured cowbird abundance and host density and located and monitored vireo nests in pinyon-juniper and mixed-conifer habitats that ranged from actively grazed to isolated from livestock grazing by up to 12 km. Cowbird abundance declined with distance from active livestock grazing and was not related to host density or habitat type. Brood parasitism levels of vireo nests ( n = 182) decreased from> 80% in actively grazed habitats to 33% in habitats that were 8–12 km from active grazing but did not vary by habitat type or distance to forest edge. Vireo nesting success was higher in mixed-conifer habitat than in pinyon-juniper but was unrelated to distance from active livestock grazing. Nest losses due to parasitism declined with distance from active livestock grazing. Our results suggest that cowbird abundance and parasitism rates of hosts may be distributed as a declining gradient based on distance from cowbird feeding sites and that isolation from feeding sites can reduce the effects of parasitism on host populations. These findings provide support for management techniques that propose to reduce local cowbird numbers and parasitism levels by manipulating the distribution of cowbird feeding sites. The presence of parasitized nests> 8 km from active livestock grazing suggests that, in some regions, management efforts may need to occur at larger scales than previously realized.     

Effect of gaseous chlorine dioxide on indoor microbial contaminants

Traditional and modern techniques for bioaerosol enumeration were used to evaluate the relative efficiency of gaseous chlorine dioxide (ClO2) in reducing the indoor microbial contamination under field and laboratory conditions. The field study was performed in a highly microbially contaminated house, which had had an undetected roof leak for an extended period of time and exhibited large areas of visible microbial growth. Air concentrations of culturable fungi and bacteria, total fungi determined by microscopic count and polymerase chain reaction (PCR) assays, endotoxin, and (1 --> 3)-beta-D-glucan were determined before and after the house was tented and treated with ClO2. The laboratory study was designed to evaluate the efficiency of ClO2 treatment against known concentrations of spores of Aspergillus versicolor and Stachybotrys chartarum on filter paper (surrogate for surface treatment). These species are commonly found in damp indoor environments and were detected in the field study. Upon analysis of the environmental data from the treated house, it was found that the culturable bacteria and fungi as well as total count of fungi (as determined by microscopic count and PCR) were decreased at least 85% after the ClO2 application. However, microscopic analyses of tape samples collected from surfaces after treatment showed that the fungal structures were still present on surfaces. There was no statistically significant change in airborne endotoxin and (1 --> 3)-beta-D-glucan concentration in the field study. The laboratory study supported these results and showed a nonsignificant increase in the concentration of (1 --> 3)-beta-D-glucan after ClO2 treatment.     

Temporal and Spatial Trends in Nutrient and Sediment Loading to Lake Tahoe,California‐Nevada,USA

Since 1980, the Lake Tahoe Interagency Monitoring Program (LTIMP) has provided stream‐discharge and water quality data—nitrogen (N), phosphorus (P), and suspended sediment—at more than 20 stations in Lake Tahoe Basin streams. To characterize the temporal and spatial patterns in nutrient and sediment loading to the lake, and improve the usefulness of the program and the existing database, we have (1) identified and corrected for sources of bias in the water quality database; (2) generated synthetic datasets for sediments and nutrients, and resampled to compare the accuracy and precision of different load calculation models; (3) using the best models, recalculated total annual loads over the period of record; (4) regressed total loads against total annual and annual maximum daily discharge, and tested for time trends in the residuals; (5) compared loads for different forms of N and P; and (6) tested constituent loads against land use‐land cover (LULC) variables using multiple regression. The results show (1) N and P loads are dominated by organic N and particulate P; (2) there are significant long‐term downward trends in some constituent loads of some streams; and (3) anthropogenic impervious surface is the most important LULC variable influencing water quality in basin streams. Many of our recommendations for changes in water quality monitoring and load calculation methods have been adopted by the LTIMP.     

Ammonia emission from grassland and livestock production systems in the UK

Emissions of ammonia were measured from livestock excreta and fertilisers applied to grass swards, from grazed paddocks, from decomposing grass herbage and from an animal house containing dairy cows. Emissions from urine, dung, slurry and fertilisers were determined using a system of wind tunnels with each tunnel covering an area of 1 m(2). Emissions from grazed swards were determined using a micrometeorological mass balance method. From the results of these measurements, together with other published information, an inventory for ammonia emissions has been calculated for grassland and livestock production systems over the UK as a whole. It is estimated that emissions from grassland and cattle and sheep production amount to about 230 kt NH(3)-N annually, while emissions from pig and poultry production amount to about 40 kt and 80 kt NH(3)-N, respectively.     

Impacts of atmospheric pollution on the plant communities of British acid grasslands

Air pollutants are recognised as important agents of ecosystem change but few studies consider the effects of multiple pollutants and their interactions. Here we use ordination, constrained cluster analysis and indicator value analyses to identify potential environmental controls on species composition, ecological groupings and indicator species in a gradient study of UK acid grasslands. The community composition of these grasslands is related to climate, grazing, ozone exposure and nitrogen deposition, with evidence for an interaction between the ecological impacts of base cation and nitrogen deposition. Ozone is a key agent in species compositional change but is not associated with a reduction in species richness or diversity indices, showing the subtly different drivers on these two aspects of ecosystem degradation. Our results demonstrate the effects of multiple interacting pollutants, which may collectively have a greater impact than any individual agent.     

Hesperidin protects against aluminum-induced renal injury in rats via modulating MMP-9 and apoptosis: biochemical,histological, and ultrastructural study

Environmental Science and Pollution Research - Aluminum, one of the most abundant metallic elements, is known to be toxic to multiple organs including the kidneys. This study aimed to investigate...     

Odd fish abandon mixed-species groups when threatened

Summary In a field experiment, two juvenile size classes of striped parrotfish (Scarus iserti), stoplight light parrotfish (Sparisoma viride), and ocean surgeonfish (Acanthurus bahianus) were threatened by a model of a common predator (the trumpetfish, Aulostomus maculatus) while alone and in mixedspecies groups of 3–100 members. Striped parrotfish, which usually consitute the majority of a group, used the groups for protection. Stopight parrotfish, present in very low numbers, hid in the coral. Individuals of both species left a group sooner if it had fewer conspecifics. Small surgeonfish sought protection in groups, while larger individuals too big to be consumed by the trumpetfish, swam away alone. These results may be explained by differences in the protection derived from mixed-species groups, and particularly, by the high predation risk suffered by odd individuals.     

Identification and investigation of properties of social support

In response to the charge by House and Kahn (1985) that there is lack of specificity in conceptualization and measurement of the social support construct, this paper suggests the need to identify and specifically measure discrete properties of the previously identified dimensions (type and source) of social support. Properties are defined as what it is about combinations of source and type that needs to be measured. Based on literature reviews it is suggested that the relevant properties are amount of support, adequacy of support and number of providers of support. Measures are developed for each property. Data from 186 nurses were used to assess main and moderating effects of social support properties, workload and dying patients on emotional exhaustion and physical symptoms. As predicted, support adequacy was related to perceptions of lower workload. As single predictors, amount and adequacy of support reduced physical symptoms and emotional exhaustion. With amount and adequacy controlled, number of providers increased emotional exhaustion. Amount buffered the relationship between death and emotional exhaustion. Moderate levels of adequacy and number buffered the relationship between workload and exhaustion. Both adequacy and amount of support assisted in coping with patient death. In addition, a number of ‘reverse’ buffering and coping relationships were found. It was concluded that examination of different properties of social support increases our understanding of the impact of social support, and that further research needs to examine the simultaneous effects of various combinations of property, type and source of social support.     

Alpha-fetoprotein and acetylcholinesterase in twins discordant for neural tube defect

Twins concordant for elevated alpha-fetoprotein (AFP) and acetylcholinesterase (AChE) and discordant for neural tube defect (NTD) and sex are reported. A literature review reveals instances of termination of twin pregnancies with one normal and one abnormal fetus, partly based on concordant high AFP and positive AChE (although discordant on ultrasound examination). The levels of AFP and AChE in twin pregnancies are probably a function of the number of layers of fetal membranes separating twin sacs: dichorionic, diamniotic membranes allow transfer of AFP; monochorionic, diamniotic membranes allow transfer of both AFP and AChE. Cautious interpretation of biochemical findings and reliance on high resolution ultrasonography are suggested.