Factors affecting aural detections of songbirds.

Many factors affect the number of birds detected on point count surveys of breeding songbirds. The magnitude and importance of these factors are not well understood. We used a bird song simulation system to quantify the effects of detection distance, singing rate, species differences, and observer differences on detection probabilities of birds detected by ear. We simulated 40 point counts consisting of 10 birds per count for five primary species (Black-and-white Warbler Mniotilta varia, Black-throated Blue Warbler Dendroica caerulescens, Black-throated Green Warbler Dendroica virens, Hooded Warbler Wilsonia citrina, and Ovenbird Seiurus aurocapillus) over a range of 15 distances (34-143 m). Songs were played at low (two songs per count) and high (13-21 songs per count) singing rates. Detection probabilities averaged across observers ranged from 0.60 (Black-and-white Warbler) to 0.83 (Hooded Warbler) at the high singing rate and 0.41 (Black-and-white Warbler) to 0.67 (Hooded Warbler) at the low singing rate. Logistic regression analyses indicated that species, singing rate, distance, and observer were all significant factors affecting detection probabilities. Singing rate x species and singing rate X distance interactions were also significant. Simulations of expected counts, based on the best logistic model, indicated that observers detected between 19% (for the worst observer, lowest singing rate, and least detectable species) and 65% (for the best observer, highest singing rate, and most detectable species) of the true population. Detection probabilities on actual point count surveys are likely to vary even more because many sources of variability were controlled in our experiments. These findings strongly support the importance of adjusting measures of avian diversity or abundance from auditory point counts with direct estimates of detection probability.     

Factors influencing movement probabilities of big brown bats (Eptesicus fuscus) in buildings.

We investigated movements of female big brown bats (Eptesicus fuscus) roosting in maternity colonies in buildings in Fort Collins, Colorado (USA), during the summers of 2002, 2003, and 2005. This behavior can be of public health concern where bats that may carry diseases (e.g., rabies) move among buildings occupied by people. We used passive integrated transponders (PIT tags) to mark individual bats and hoop PIT readers at emergence points to passively monitor the use of building roosts by marked adult females on a daily basis during the lactation phase of reproduction. Multi-strata models were used to examine movements among roosts in relation to ambient temperatures and ectoparasite loads. Our results suggest that high ambient temperatures influence movements. Numbers of mites (Steatonyssus occidentalis) did not appear to influence movements of female bats among building roosts. In an urban landscape, periods with unusually hot conditions are accompanied by shifting of bats to different buildings or segments of buildings, and this behavior may increase the potential for contact with people in settings where, in comparison to their more regularly used buildings, the bats may be more likely to be of public concern as nuisances or health risks.     

Feeding biology and ecological impact of an introduced nudibranch,Tritonia plebeia,New England,USA

The nudibranchTritonia plebeia (Johnston) was first observed in New England in 1983, on vertical rock walls at 7 m depth off Nahant, Massachusetts. This northern European species preys exclusively on the soft coralAlcyonium digitatum (Linneaus) in its natural habitat. At Nahant, it preyed primarily on the closely relatedAlcyonium siderium Verrill. Laboratory studies indicated that it could locate its prey by distance chemoreception and by visual orientation towards tall dark surfaces which could help it find the vertical walls, overhangs, and boulder sides where the soft corals occur. Field studies showed thatT. plebeia fed primarily on colony bases, causing extensive damage and whole colony mortality. The most important endemic predator onA. siderium, Coryphella verrucosa (Sars), preyed preferentially on hydroids, but would graze polyps off the top portions ofA. sederium colonies, causing little permanent damage to the colony, during the winter months when hydroids were scarce. AlthoughC. verrucosa occasionally behaved agonistically towardT. plebeia, there was no indication in laboratory or field studies that either nudibranch had an effect on the other's foraging through interference competition. Extensive predation byT. plebeia caused the disappearance ofA. siderium at two sites (Outer and Inner Shag Rocks) and a sharp reduction at a third site (Inner East Point). The higher mortalities at the Shag Rocks sites most likely occurred because of a simultaneous urchin (Strogylocentrotus droebachiensis) population expansion. As space among aggregates ofA. siderium opened up due toT. plebeia predation, urchins were able to forage on the vertical walls and scrape off remaining colonies. At a fourth site, Halfway Rock, whereT. plebeia were seldom present,A. siderium colonies also suffered high mortalities. This increae in mortality began nearly a year before urchin populations increased, and during a summer of abnormally high water temperatures at Halfway Rock. The high temperatures, followed by urchin predation on remaining colonies could account for the disappearance of allA. siderium colonies at this site.T. plebeia disappeared at all sites by summer 1986 andA. siderium populations have since stabilized, but community-level changes at all sites whereA. siderium were removed have persisted.     

Factors influencing the photodegradation of N-nitrosodimethylamine in drinking water

In order to provide basic data for practical application, photodegradation experiment of N-nitrosodimethylamine (NDMA) in aqueous solution was carried out with a low-pressure Hg lamp. Effects of the initial concentration of NDMA, solution pH, dissolved oxygen, and the presence of humic acid on NDMA photodegradation were investigated. NDMA at various initial concentrations selected in this study was almost completely photodegraded by UV irradiation within 20 min, except that at 1.07 mmol/L, NDMA could be photodegraded almost completely in the acidic and neutral solutions, while the removal efficiency decreased remarkably in the alkaline solution. Dissolved oxygen enhanced the NDMA photodegradation, and the presence of humic acid inhibited the degradation of NDMA. Depending on the initial concentration of NDMA, NDMA photodegradation by UV obeyed the pseudo-first-order kinetics. Dimethylamine, nitrite, and nitrate were detected as the photodegradation products of NDMA. ¹O₂ was found to be the reactive oxygen species present in the NDMA photodegradation process by UV, based on the inhibiting experiments using tert-butanol and sodium azide.     

Independent effects of fragmentation on forest songbirds: an organism-based approach.

The degree to which spatial patterns influence the dynamics and distribution of populations is a central question in ecology. This question is even more pressing in the context of rapid habitat loss and fragmentation, which threaten global biodiversity. However, the relative influence of habitat loss and landscape fragmentation, the spatial patterning of remaining habitat, remains unclear. If landscape pattern affects population size, managers may be able to design landscapes that mitigate habitat loss. We present the results of a mensurative experiment designed to test four habitat loss vs. fragmentation hypotheses. Unlike previous studies, we measured landscape structure using quantitative, spatially explicit habitat distribution models previously developed for two species: Blackburnian Warbler (Dendroica fusca) and Ovenbird (Seiurus aurocapilla). We used a stratified sampling design that reduced the confounding of habitat amount and fragmentation variables. Occurrence and reoccurrence of both species were strongly influenced by characteristics at scales greater than the individual territory, indicating little support for the random-sample hypothesis. However, the type and spatial extent of landscape influence differed. Both occurrence and reoccurrence of Blackburnian Warblers were influenced by the amount of poor-quality matrix at 300- and 2000-m spatial extents. The occurrence and reoccurrence of Ovenbirds depended on a landscape pattern variable, patch size, but only in cases when patches were isolated. These results support the hypothesis that landscape pattern is important for some species only when the amount of suitable habitat is low. Although theoretical models have predicted such an interaction between landscape fragmentation and composition, to our knowledge this is the first study to report empirical evidence of such nonlinear fragmentation effects. Defining landscapes quantitatively from an organism-based perspective may increase power to detect fragmentation effects, particularly in forest mosaics where boundaries between patches and matrix are ambiguous. Our results indicate that manipulating landscape pattern may reduce negative impacts of habitat loss for Ovenbird, but not Blackburnian Warbler. We emphasize that most variance in the occurrence of both species was explained by local scale or landscape composition variables rather than variables reflecting landscape pattern.     

Factors influencing the gas composition in the vesicles of Sargassum

The composition of gas in the vesicles of Sargassum cf. leptopodum Sonder has been investigated. The oxygen content depends upon the oxygen partial pressure of the surrounding medium. It does not depend upon the photosynthetic activity of the vesicle. Evidence is provided that the lower limit of the vertical distribution zone of Sargassum cf. leptopodum Sonder is not controlled by the vesicles' capability of resisting hydrostatic pressure.     

Factors influencing clustering in the intertidal snail Cerithium moniliferum

The snail Cerithium moniliferum Kiener at Heron Island (southern end of the Great Barrier Reef) clusters at outgoing tide and disperses at incoming tide. In containers with a constant water level, but exposed to the normal day and night rhythm, the snails cluster and disperse rhythmically for up to several days. Graphical simulation and spectral analysis, preceded by first difference filtering, showed two components, one corresponding to the tidal, and the other to the diurnal rhythm. Snails kept under continuous light also exhibit a two-component rhythm of clustering and dispersal. In containers with high (40 cm) water level and under continuous light or normal day and night rhythm, the two-component rhythm may—for some unknown reason—be replaced by long fluctuations of dispersal, with clustering occurring in the afternoon only in snails kept under normal alternation of day and night. Snails kept for 24 h in dryness prior to putting them into containers with water, remain clustered (sometimes with an initial dispersal “shock”) for a long time, with subsequent slow fluctuations of clustering and dispersal, probably induced by the light conditions. Factors contributing to clustering and dispersal are: (1) increased rate of dropping from container walls at outgoing tide; (2) lack of locomotory activity at low tide; (3) negative geotaxis at incoming tide; (4) positive geotaxis at outgoing tide; (5) attraction of snails by other snails (positive chemotaxis) throughout the rhythm. Sudden exposure to light increases the rate of dropping from the container walls and may be a contributing factor to stronger clustering during the day. Factors 1–4 show endogenous periodicities.     

Factors influencing corrosion of metal pipes in soils

Deterioration of buried metal pipes due to corrosive soil environment is a major issue worlwide. Although failures of buried pipe due to corrosive soil is an old problem, yet such failures are still uncontrollable even with the application of advanced corrosion protection technologies. Therefore, understanding factors causing corrosion of buried pipes is necessary. This article reviews factors causing corrosion of buried pipes in soils. Factors include moisture content, soil resistivity, pH, dissolved oxygen, temperature and microbial activity. Moreover, we discuss the influence of manufacturing method and the comparison of corrosion behaviour of cast iron, ductile and mild steel pipes. We found that corrosion rate of pipes increases with moisture contents up to the critical moisture value. Although pH affects corrosion, there is no relationship between corrosion and pH and the corrosion rates of buried pipes are inversely proportional to soil resistivity. Soils containing more organic matter show high resistivity. Dissolved oxygen in soil develops differential cell which accelerates corrosion of metallic pipe. Different types of bacteria present in soil develop biofilms on metallic pipes, which deteriorates pipes with time.     

Factors influencing egg size in the gammarid amphipod Gammarus insensibilis

Developmental and seasonal changes in egg volume were examined in a population of the amphipod Gammarus insensibilis Stock occurring on the south coast of England, towards its northern limit of distribution. Results showed a marked increase in egg volume during development (2.9 times by Egg Stage V), resulting from water uptake and from the conversion of yolk reserves into structural elements. The maximum rate of increase coincides with the period of organ and limb development. At hatching, after initial rupture of the egg membrane by urosome spines, egg volume increases rapidly over a short period (15 to 20 min) by a further 30% (uptake rate 3.6×10^–5 mm³s^–1), followed by a post-hatching decrease in juvenile volume. Increase in size at hatching is the result of drinking by embryos, although changes in body-wall permeability may contribute. Females carrying eggs in an advanced stage of development exhibit egg-collecting behaviour. This is seen as an adaptation to an increased likelihood of egg loss with increase in volume of the brood as hatching approaches. Seasonal changes in Stage I (early) egg size are marked in this species, with winter eggs as much as 60% greater in volume than summer eggs. Egg size is inversely related to the temperature during oocyte development. A simple model has been derived to account for the observed seasonal pattern in egg size. The consequences of seasonal variation in egg and juvenile size are considered.     

Phylogenetic,ecological, and ontogenetic factors influencing the biochemical structure of the blubber of odontocetes

To explore ecological, phylogenetic, and developmental factors affecting the structure of blubber in Odontocetes (toothed whales), lipid composition of this specialized adipose tissue was determined in 260 specimens (30 species representing all families except the river dolphins), most of which were collected between 1995 and 2005, from all over the world. In most odontocetes, blubber contained primarily triacylglycerols; the blubber of beaked and sperm whales was dominated by wax esters (WE), exhibiting ontogenetic patterns of deposition. WEs may represent an adaptation to deep diving for marine mammals that do not rely on blubber for stored energy. Fatty acid (FA) composition was stratified through blubber depth, with higher concentrations of dietary FA in the inner and endogenous FA in the outer layers of the blubber. Stratification can be considered a characteristic feature of odontocetes, and is likely the result of differential metabolism through the blubber. Small body size appears to constrain blubber lipid content to be high. Thermal habitat also represents an important selective pressure for blubber composition. Species inhabiting colder waters exhibited both higher lipid content and increased FA stratification in blubber, compared to species from warm/tropical habitats. The isolation of mobilization to inner blubber may permit metabolic enzymes to function without limitation by lower temperatures. The variation in composition and distribution of blubber lipids in odontocetes suggests that different species may have evolved slightly diverse arrays of secondary functions for this specialized tissue as adaptations for specific ecological niches. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Allowable levels of take for the trade in Nearctic songbirds

The take of Nearctic songbirds for the caged-bird trade is an important cultural and economic activity in Mexico, but its sustainability has been questioned. We relied on the theta-logistic population model to explore options for setting allowable levels of take for 11 species of passerines that were subject to legal take in Mexico in 2010. Because estimates of population size necessary for making-periodic adjustments to levels of take are not routinely available, we examined the conditions under which a constant level of take might contribute to population depletion (i.e., a population below its level of maximum net productivity). The chance of depleting a population is highest when levels of take are based on population sizes that happen to be much lower or higher than the level of maximum net productivity, when environmental variation is relatively high and serially correlated, and when the interval between estimation of population size is relatively long (> or = 5 years). To estimate demographic rates of songbirds involved in the Mexican trade we relied on published information and allometric relationships to develop probability distributions for key rates, and then sampled from those distributions to characterize the uncertainty in potential levels of take. Estimates of the intrinsic rate of growth (r) were highly variable, but median estimates were consistent with those expected for relatively short-lived, highly fecund species. Allowing for the possibility of nonlinear density dependence generally resulted in allowable levels of take that were lower than would have been the case under an assumption of linearity. Levels of take authorized by the Mexican government in 2010 for the 11 species we examined were small in comparison to relatively conservative allowable levels of take (i.e., those intended to achieve 50% of maximum sustainable yield). However, the actual levels of take in Mexico are unknown and almost certainly exceed the authorized take. Also, the take of Nearctic songbirds in other Latin American and Caribbean countries ultimately must be considered in assessing population-level impacts.     

Optimisation of adjusted barrier management to improve glass eel migration at an estuarine barrier

Estuarine barriers may significantly reduce the upstream migration of diadromous fish species like the European eel (Anguilla anguilla L.). Previous research showed that limited barrier opening during tidal rise was a cost-efficient and effective mitigation option to improve upstream glass eel migration, without significant intrusion of sea water. This paper aims to optimise this adjusted barrier management to improve eel passage at a tidal barrier complex at the mouth of the River Yser, Flanders, Belgium, one of the most important migration routes for glass eel in Flanders. Specifically, three hypotheses were tested. The first hypothesis analysed the impact of the number of barriers opened on the upstream glass eel migration. The second hypothesis evaluated the relation between the size of the barrier opening and glass eel migration. Finally, we tested whether the suggested adjusted barrier management may lead to a significant increase in conductivity in the River Yser. Increased opening of one barrier appeared more efficient than opening several barriers slightly. Conductivity increased during periods of extreme drought and at base flow, but decreased within 24 h after the first peak flow. This indicates that adjusted barrier management does not entail salt intrusion in the Yser basin, as long as this management is not applied in extremely dry periods. Since the adjusted barrier management is easily implemented and could be applied on numerous tidal barriers, the presented results may contribute to restoration of eel populations worldwide and be of interest to a wide range of river managers and stakeholders.     

Inferring ecological and behavioral drivers of African elephant movement using a linear filtering approach

Understanding the environmental factors influencing animal movements is fundamental to theoretical and applied research in the field of movement ecology. Studies relating fine-scale movement paths to spatiotemporally structured landscape data, such as vegetation productivity or human activity, are particularly lacking despite the obvious importance of such information to understanding drivers of animal movement. In part, this may be because few approaches provide the sophistication to characterize the complexity of movement behavior and relate it to diverse, varying environmental stimuli. We overcame this hurdle by applying, for the first time to an ecological question, a finite impulse-response signal-filtering approach to identify human and natural environmental drivers of movements of 13 free-ranging African elephants (Loxodonta africana) from distinct social groups collected over seven years. A minimum mean-square error (MMSE) estimation criterion allowed comparison of the predictive power of landscape and ecological model inputs. We showed that a filter combining vegetation dynamics, human and physical landscape features, and previous movement outperformed simpler filter structures, indicating the importance of both dynamic and static landscape features, as well as habit, on movement decisions taken by elephants. Elephant responses to vegetation productivity indices were not uniform in time or space, indicating that elephant foraging strategies are more complex than simply gravitation toward areas of high productivity. Predictions were most frequently inaccurate outside protected area boundaries near human settlements, suggesting that human activity disrupts typical elephant movement behavior. Successful management strategies at the human-elephant interface, therefore, are likely to be context specific and dynamic. Signal processing provides a promising approach for elucidating environmental factors that drive animal movements over large time and spatial scales.     

Toward an ecological classification of soil bacteria

Although researchers have begun cataloging the incredible diversity of bacteria found in soil, we are largely unable to interpret this information in an ecological context, including which groups of bacteria are most abundant in different soils and why. With this study, we examined how the abundances of major soil bacterial phyla correspond to the biotic and abiotic characteristics of the soil environment to determine if they can be divided into ecologically meaningful categories. To do this, we collected 71 unique soil samples from a wide range of ecosystems across North America and looked for relationships between soil properties and the relative abundances of six dominant bacterial phyla (Acidobacteria, Bacteroidetes, Firmicutes, Actinobacteria, alpha-Proteobacteria, and the beta-Proteobacteria). Of the soil properties measured, net carbon (C) mineralization rate (an index of C availability) was the best predictor of phylum-level abundances. There was a negative correlation between Acidobacteria abundance and C mineralization rates (r2 = 0.26, P < 0.001), while the abundances of beta-Proteobacteria and Bacteroidetes were positively correlated with C mineralization rates (r2 = 0.35, P < 0.001 and r2 = 0.34, P < 0.001, respectively). These patterns were explored further using both experimental and meta-analytical approaches. We amended soil cores from a specific site with varying levels of sucrose over a 12-month period to maintain a gradient of elevated C availabilities. This experiment confirmed our survey results: there was a negative relationship between C amendment level and the abundance of Acidobacteria (r2 = 0.42, P < 0.01) and a positive relationship for both Bacteroidetes and beta-Proteobacteria (r2 = 0.38 and 0.70, respectively; P < 0.01 for each). Further support for a relationship between the relative abundances of these bacterial phyla and C availability was garnered from an analysis of published bacterial clone libraries from bulk and rhizosphere soils. Together our survey, experimental, and meta-analytical results suggest that certain bacterial phyla can be differentiated into copiotrophic and oligotrophic categories that correspond to the r- and K-selected categories used to describe the ecological attributes of plants and animals. By applying the copiotroph-oligotroph concept to soil microorganisms we can make specific predictions about the ecological attributes of various bacterial taxa and better understand the structure and function of soil bacterial communities.     

Factors influencing food choice by the seaweed-eating marine snail Norrisianorrisi (Trochidae)

Through two-choice gustatory experiments, a␣preference hierarchy was established␣for␣the␣herbivorous gastropod Norrisianorrisi Sowerby, with laminarialean kelps preferred over all other seaweeds. Among the kelps, laminae of Macrocystispyrifera were slightly preferred over Egregiamenziesii, and both were strongly preferred over sporophylls of Eiseniaarborea. E.arborea, the least preferred kelp, was consistently chosen over other algae common in the snail's habitat (Halidrysdioica, Dictyotaflabellata, and Pterocladiacapillacea) and over seaweeds believed to be edible and palatable based on their morphology, structure, and secondary chemistry (Endarachnebinghamiae, Mazzaellaflaccida, and Ulvalobata). The morphologies and structural toughness of tested seaweeds varied significantly as did their nutritional (% carbon, % nitrogen, C:N ratio, and % ash) contents and phlorotannin concentrations; however, snails preferred to feed on kelps regardless of nutritional content, toughness or phlorotannin concentration; and among kelps preferred to feed on the least tough species (based on penetrometer measurements), which also were those containing the lowest phlorotannin concentrations. Preference for kelp was not upheld in experiments using agarose thalli to which freeze-dried powder, of either the kelp Eiseniaarborea or non-kelp Endarachnebinghamiae was added, suggesting the destruction of attractant chemicals during the making of the artificial foods. Our data suggest that the preference of N. norrisi for kelps over other potentially edible and palatable seaweeds may not be related to nutritional content, but instead may have evolved in response to factors such as availability, habitat provision, or refuge from predation. Received: 27 September 1996 / Accepted: 7 October 1997     

Factors influencing cannibalism in the wolf spider Pardosa agrestis (Araneae, Lycosidae)

Cannibalistic tendencies are well known in spiders and may be a significant factor influencing population size. The wolf spider, Pardosa agrestis, is the dominant non-web-building spider in a wide range of central European agricultural habitats. Preliminary field observations indicated an extended reproductive period, which results in a very wide size distribution of juvenile instars. We hypothesised that if cannibalism is enhanced by differences in size, especially during periods when prey is scarce, these populations might be susceptible to cannibalism in an ecologically significant way. Laboratory studies were conducted on juvenile P. agrestis in arenas. We analysed the following specific aspects of cannibalism: (1) the effect of the weight ratio between the opponents; (2) the effect of weight per se, and (3) the role of hunger level in determining cannibalistic tendencies of spiders. The role of weight and hunger were analysed in separate experiments, in both cases by controlling for the other variable. The results showed that cannibalism was strongly positively correlated with both weight ratio and hunger, but absolute size/age of an individual could not predict the occurrence of a cannibalistic event. These experiments generated the plausible hypothesis that cannibalism might be an important phenomenon in the regulation of real populations, which should be tested specifically in future field experiments. Received: 15 December 1997 / Accepted after revision: 10 October 1998     

Factors influencing the willingness to pay for sustainable tourism: a case of mass tourism destinations

A 17-month research programme focused on development of an Education for Sustainability (EFS) Global Media Network at Ball State University Indiana was recently concluded. The study results include some surprising conclusions related to the contradictions between the benefits of education for global sustainability and the use of technology to facilitate that educational process in achieving a more sustainable world. This article provides an overview of the EFS Network research programme and a discussion of some of the key results and conclusions related to advantages and disadvantages of technology-based learning. The article then addresses the environmental impact of computer technology manufacturing, use, and after-use. Research findings are utilized to illustrate the ecological footprint of computer-based education. The article concludes with a discussion about achieving a balance between the need for global-to-local sustainable education and the environmental impact of technology use for sustainable education.     

Factors influencing incidental representation of previously unknown conservation features in marine protected areas

Spatially explicit information on species distributions for conservation planning is invariably incomplete; therefore, the use of surrogates is required to represent broad‐scale patterns of biodiversity. Despite significant interest in the effectiveness of surrogates for predicting spatial distributions of biodiversity, few researchers have explored questions involving the ability of surrogates to incidentally represent unknown features of conservation interest. We used the Great Barrier Reef marine reserve network to examine factors affecting incidental representation of conservation features that were unknown at the time the reserve network was established. We used spatially explicit information on the distribution of 39 seabed habitats and biological assemblages and the conservation planning software Marxan to examine how incidental representation was affected by the spatial characteristics of the features; the conservation objectives (the minimum proportion of each feature included in no‐take areas); the spatial configuration of no‐take areas; and the opportunity cost of conservation. Cost was closely and inversely correlated to incidental representation. However, incidental representation was achieved, even in a region with only coarse‐scale environmental data, by adopting a precautionary approach that explicitly considered the potential for unknown features. Our results indicate that incidental representation is enhanced by partitioning selection units along biophysical gradients to account for unknown within‐feature variability and ensuring that no‐take areas are well distributed throughout the region; by setting high conservation objectives that (in this case >33%) maximize the chances of capturing unknown features incidentally; and by carefully considering the designation of cost to planning units when using decision‐support tools for reserve design. The lessons learned from incidental representation in the Great Barrier Reef have implications for conservation planning in other regions, particularly those that lack detailed environmental and ecological data.