Latitudinal Variation in Seasonal Activity and Mortality in Ratsnakes (Elaphe obsoleta)

The ecology of ectotherms should be particularly affected by latitude because so much of their biology is temperature dependent. Current latitudinal patterns should also be informative about how ectotherms will have to modify their behavior in response to climate change. We used data from a total of 175 adult black ratsnakes (Elaphe obsoleta) radio tracked in Ontario, Illinois, and Texas, a latitudinal distance of \u3e 1500 km, to test predictions about how seasonal patterns of activity and mortality should vary with latitude. Despite pronounced differences in temperatures among study locations, and despite ratsnakes in Texas not hibernating and switching from diurnal to nocturnal activity in the summer, seasonal patterns of snake activity were remarkably similar during the months that snakes in all populations were active. Rather than being a function of temperature, activity may be driven by the timing of reproduction, which appears similar among populations. Contrary to the prediction that mortality should be highest in the most active population, overall mortality did not follow a clinal pattern. Winter mortality did increase with latitude, however, consistent with temperature limiting the northern distribution of ratsnakes. This result was opposite that found in the only previous study of latitudinal variation in winter mortality in reptiles, which may be a consequence of whether or not the animals exhibit true hibernation. Collectively, these results suggest that, at least in the northern part of their range, ratsnakes should be able to adjust easily to, and may benefit from, a warmer climate, although climate-based changes to the snakes\u27 prey or habitat, for example, could alter that prediction

Avian Range Extension Northward to Deception Bay, Quebec

From 19 to 23 July 1979, the authors conducted surveys by foot of the avifauna of Deception Bay, Quebec (62 deg. 07 sec. N, 74 deg. 40 sec. W). ... Sightings and evidence of Tree Sparrows were limited to areas of mixed shrub habitat dominated by Dwarf Birch ... and several species of willow .... Also associated only with this habitat were redpolls ... Savannah Sparrows ... and White-crowned Sparrows .... A sighting warranting further investigation was that of a pair of Hoary Redpolls ...

Climate change impacts on water for irrigated horticulture in the Vale of Evesham. Final Report

This project has undertaken a scoping review and assessment of the impacts of climate change on irrigated horticulture in the Vale of Evesham, an area of intense irrigated production located within the Environment Agency’s Warwickshire Avon CAMS Catchment. The research was based on a combination of methodologies including desk-based review of published and grey literature, computer agroclimatic and water balance modelling, GIS mapping, meetings with key informants and a stakeholder workshop. Future climate datasets were derived from the latest UK Climate Impacts Programme (UKICIP02) climatology, using selected emission scenarios for the 2020s, 2050s and 2080s. These scenarios were then used to model and map the future agroclimatic conditions under which agriculture might operate and the consequent impacts on irrigation need (depths of water applied) and volumetric demand. This was complimented by a postal survey to abstractors and a stakeholder workshop, to identify, review and assess farmer adaptation options and responses. The key findings arising from the research, implications for water resource management and recommendations for further work are summarised below. Using a geographical information system (GIS), a series of agroclimate maps have been produced, for the baseline and selected UKCIP02 scenario. The maps show major changes in agroclimate within the catchment over the next 50 years. The driest agroclimate zones are currently located around Worcester, Evesham, Tewkesbury and Gloucester, corresponding to areas where horticultural production and irrigation demand are most concentrated. By the 2020s, all agroclimate zones are predicted to increase in aridity. By the 2050s the entire catchment is predicted to have a drier agroclimate than is currently experienced anywhere in the driest parts of the catchment. This will have major impacts on the pattern of land use and irrigation water demand. Cont/d

USE OF INHALANT ANESTHETICS IN THREE SNAKE SPECIES

Different snake species respond differently to various anesthetic agents. Hence, an anesthetic procedure developed for one species cannot necessarily be safely transferred to another species. The goal of this paper is to summarize our experience using inhalant anesthetics on three snake species, including both procedures that were successful and those we found to be less satisfactory. We found isoflurane delivered with a precision vaporizer to be the best agent to anesthetize black rat snakes (Elaphe o. obsoleta). Sex and mass did not seem to affect induction times in black rat snakes, but larger female rat snakes recovered faster from anesthesia than smaller females. Halothane delivered in the open method provided consistent anesthesia in northern water snakes (Nerodia s. sipedon), although it caused some mortality and should not be used on debilitated patients. Halothane delivered with a precision vaporizer may be used to anesthetize eastern massasauga rattlesnakes (Sistrurus c. catenatus). However, care must be taken to prevent mortality resulting from anesthetic overdose. Sex and mass had no effect on induction and recovery times in the rattlesnakes, but stressed animals require longer induction and recovery times

Linking Snake Behavior to Nest Predation in a Midwestern Bird Community

Nest predators can adversely affect the viability of songbird populations, and their impact is exacerbated in fragmented habitats. Despite substantial research on this predator-prey interaction, however, almost all of the focus has been on the birds rather than their nest predators, thereby limiting our understanding of the factors that bring predators and nests into contact. We used radiotelemetry to document the activity of two snake species (rat snakes, Elaphe obsoleta; racers, Coluber constrictor) known to prey on nests in Midwestern bird communities and simultaneously monitored 300 songbird nests and tested the hypothesis that predation risk should increase for nests when snakes were more active and in edge habitat preferred by both snake species. Predation risk increased when rat snakes were more active, for all nests combined and for two of the six bird species for which we had sufficient nests to allow separate analyses. This result is consistent with rat snakes being more important nest predators than racers. We found no evidence, however, that nests closer to forest edges were at greater risk. These results are generally consistent with the one previous study that investigated rat snakes and nest predation simultaneously. The seemingly paradoxical failure to find higher predation risk in the snakes\u27 preferred habitat (i.e., edge) might be explained by the snakes using edges at least in part for non-foraging activities. We propose that higher nest predation in fragmented habitats (at least that attributable to snakes) results indirectly from edges promoting larger snake populations, rather than from edges directly increasing the risk of nest predation by snakes. If so, the notion of edges per se functioning as ecological traps merits further study

Is Cheap Talk Effective at Eliminating Hypothetical Bias in a Provision Point Mechanism?

Significant difference between response to real and hypothetical valuation questions is often referred to as hypothetical bias. Some economists have had success with using “cheap talk” (which entails reading a script that explicitly highlights the hypothetical bias problem before participants make any decisions) as a means of generating unbiased responses in a referendum format. In this article, we test the robustness of cheap talk using a voluntary contribution mechanism with a provision point over a wide range of possible payment amounts. Our results confirm the existence of hypothetical bias, and suggest that cheap talk may eliminate hypothetical bias, but only for respondents facing higher payments

SEASONAL, HABITAT AND SEX-SPECIFIC PATTERNS OF FOOD UTILIZATION BY RED-WINGED BLACKBIRDS (Agelaius phoeniceous) IN EASTERN ONTARIO AND THEIR ECONOMIC IMPORTANCE

Crop depredation by red-winged blackbirds (Agelaius phoeniceus) causes serious economic losses to agricultural crops each year in both Canada and the United States. The concentration of vulnerable, monocultural crops, particularly corn, during periods when large flocks of blackbirds congregate in roosting areas prior to migration has invariably led to heavy feeding pressure (Stone et al., 1972; Wiens and Dyer, 1975; Tyler et al., 1978). Efforts to reduce damage levels by mechanical and chemical dispersal agents have been largely unsuccessful, at least in terms of a long-term solution to the problem. Recently, the lethal control of blackbird populations using surfactants has been proposed. However, the potential repercussions of the removal of substantial numbers of birds from northern breeding areas are virtually unknown (Robertson et al., 1978). Much of the research dealing with the feeding ecology of red-winged blackbirds has been limited to fall and winter periods when large aggregations of birds are actively involved in crop depredation (Goddad, 1969; Williams, 1976; Dolbeer et al., 1978) or pose a potential health hazard (Monroe and Cronholm, 1976). However, what is not known is the degree to which the removal of deleterious weed seed and insect pests cited in several studies (Bird and Smith, 1964; Mott et al., 1972; Robertson et al., 1978) might be of potential value to agriculture. The issue of whether the benefits derived from redwing foraging compensate for the negative aspects associated with crop depredation and health hazards remains largely unresolved. The present study attempted to evaluate the pest status of this species using diet information derived from food habits analysis conducted during the residency of red- winged blackbirds in a northern breeding area. By determining how the feeding ecology of red-winged blackbirds varies on a seasonal basis, among different breeding habitats and between sexes, we hoped to determine more realistically which segments of the population might be responsible for the greatest benefits or detriments and, thereby, more accurately evaluate the economic impact of the species as a whole. To achieve this aim, the study provides an accurate description of the common insects and weed pests utilized by redwings. By determining the relative proportions of those items known to be detrimental, we hoped to illustrate, at least qualitatively, the degree to which redwing foraging is comprised of both beneficial and harmful components

A Meta-Analysis of Hypothetical Bias in Stated Preference Valuation

Individuals are widely believed to overstate their economic valuation of a good by a factor of two or three. This paper reports the results of a meta-analysis of hypothetical bias in 28 stated preference valuation studies that report monetary willingness-to-pay and that used the same mechanism for eliciting both hypothetical and actual values. The papers generated 83 observations with a median value of the ratio of hypothetical to actual value of 1.35, and the distribution has severe positive skewness. Since a comprehensive theory of hypothetical bias has not been developed, we use a set of explanatory variables based on issues that have been investigated in previous research. We find that a choice-based elicitation mechanism is important in reducing bias, though an insufficient number of studies and confounding with other variables prevents us from characterizing individual mechanisms. We provide some evidence that the use of student subjects may be a source of bias, but this variable is highly correlated with group experimental settings and no firm conclusions can be drawn. There is some weak evidence that bias increases when public goods are being valued, and that some calibration methods are effective at reducing bias. Results are quite sensitive to model specification, which will remain a problem until a comprehensive theory of hypothetical bias is developed

SPECIES COMPOSITION, FOOD HABITS, AND THE ECONOMIC AND ECOLOGIC IMPACT OF WINTER BLACKBIRD FLOCKS

Crop depredation by blackbirds (Icteridae) and Starlings (sturnus vulgaris) in North America has long prompted experimentation with control techniques. These efforts have been centered in the northeast and northcentral United States where concentrated cultivation of vulnerable crops coincides with the location where flocks of blackbirds congregate in the fall prior to their migration south (Stone, et al., 1972; Wiens and Dyer, 1975). In these areas the high cost and logistic impracticality of implementing widespread controls has suggested the need for modifying agricultural practices instead (Wiens and Dyer, 1975). More recently, attention has been focused farther south, particularly in Kentucky and Tennessee where winter roosts of mixed flocks of blackbirds and Starlings commonly number over several million birds. These highly localized concentrations have prompted concern for both agricultural damage and danger to human health (Department of Army, 1975). A major difference between the problem in the South and that farther north is that in the South the birds present themselves as much more accessible targets for control measures. By virtue of their tremendous concentrations they make the potential for large scale extermination very real. It is quite conceivable that a significant proportion of the entire North American populations of these birds could be eliminated if extermination efforts were maintained for several years at the major winter roosts. Before such extermination is allowed to proceed, a number of questions must be answered. These can be divided into two areas. The first area deals with whether or not the control measures are actually justified--how much agricultural damage is done by the birds and how real is their threat to human health? The second area of questioning concerns the environmental impact of both the control measures themselves as well as the effect of suddenly removing such large numbers of birds from the ecosystem. This paper presents the results of a preliminary study aimed not at answering these questions so much as providing some insight into the factors which must be considered if accurate answers are to be obtained

SPECIES COMPOSITION, FOOD HABITS, AND THE ECONOMIC AND ECOLOGIC IMPACT OF WINTER BLACKBIRD FLOCKS

Crop depredation by blackbirds (Icteridae) and Starlings (sturnus vulgaris) in North America has long prompted experimentation with control techniques. These efforts have been centered in the northeast and northcentral United States where concentrated cultivation of vulnerable crops coincides with the location where flocks of blackbirds congregate in the fall prior to their migration south (Stone, et al., 1972; Wiens and Dyer, 1975). In these areas the high cost and logistic impracticality of implementing widespread controls has suggested the need for modifying agricultural practices instead (Wiens and Dyer, 1975). More recently, attention has been focused farther south, particularly in Kentucky and Tennessee where winter roosts of mixed flocks of blackbirds and Starlings commonly number over several million birds. These highly localized concentrations have prompted concern for both agricultural damage and danger to human health (Department of Army, 1975). A major difference between the problem in the South and that farther north is that in the South the birds present themselves as much more accessible targets for control measures. By virtue of their tremendous concentrations they make the potential for large scale extermination very real. It is quite conceivable that a significant proportion of the entire North American populations of these birds could be eliminated if extermination efforts were maintained for several years at the major winter roosts. Before such extermination is allowed to proceed, a number of questions must be answered. These can be divided into two areas. The first area deals with whether or not the control measures are actually justified--how much agricultural damage is done by the birds and how real is their threat to human health? The second area of questioning concerns the environmental impact of both the control measures themselves as well as the effect of suddenly removing such large numbers of birds from the ecosystem. This paper presents the results of a preliminary study aimed not at answering these questions so much as providing some insight into the factors which must be considered if accurate answers are to be obtained