Victoria J. Bennett

Why the bat did not cross the road

Roadways are nearly ubiquitous parts of the modern landscape, but their impact on bats remain relatively unknown. We studied the influence of vehicular traffic on the behaviour of commuting bats near the Indianapolis International Airport. A previous study at this site documented that Indiana bats (Myotis sodalis) were much more likely to cross roads with low traffic volumes. One potential interpretation of this result is that bats perceive motor vehicles as a threat and exhibit avoidance behaviour whether or not the bats are in immediate danger. To test this hypothesis, we observed 211 cases of bats approaching roads that bisected their commuting routes. Information recorded at the time included the presence or absence of vehicles, the height the bat was flying, whether a bat reversed course prior to crossing the road and if so the distance from the road or vehicle (if present) when it altered its direction, and finally the speed, type and relative level of noise emitted by vehicles. Results revealed that bats were more than twice as likely to reverse course when vehicles were present as opposed to their absence. When automobiles were present 60% of bats exhibited avoidance behaviour, reversing course at an average of 10 m from a vehicle. Conversely, when no automobiles were present, only 32% of bats reversed their course and 68% crossed the road. The height a bat flew, speed of the vehicle, type of vehicle or level of noise emitted by vehicles had no effect on the likelihood of bats reversing course. These data support the hypothesis that bats perceive vehicles as a threat and display anti-predator avoidance behaviour in response to their presence.

Advances in sex determination in bats and its utility in wind-wildlife studies.

We developed a simple and reliable genetic method to determine sex in bats from the Vespertilionidae and Molossidae families. Polymerase chain reaction was used to amplify a portion of the introns within the zinc‐finger‐X (Zfx) and zinc‐finger‐Y (Zfy) genes. We designed primers to produce size variation between the Zfx and Zfy products that could be visualized using gel electrophoresis. Using an example from our wind‐wildlife research, we show how sex data generated using this method are superior to sex data based on external morphology. Our method allows for the generation of sex data across a wide range of bats that can be used to address key questions in wildlife forensics, behavioural ecology, conservation and evolutionary biology.

Sex-biased dispersal in a rare butterfly and the implications for its conservation

The survival of many species may be dependent on their ability to exist in human-altered landscapes within metapopulations; in turn, metapopulation persistence is dictated by the ability of individuals to move effectively among patches to promote recolonization. The Taylor’s checkerspot butterfly (Euphydryas editha taylori) is a species that does not naturally occur in fragmented landscapes, yet it is now restricted to a handful of small isolated prairie habitats. Current recovery plans aim to establish a stable metapopulation; however, to date little is known about the species’ ability to move across the landscape. In 2010 and 2011, we conducted marking, tracking and boundary surveys to explore the movement dynamics of adults within two sites in Oregon, USA. Over the survey period, we marked 136 male butterflies, tracked 174 individuals and observed the behavior of 1,576 individual butterflies at site boundaries. Our study revealed a significant sex-bias in the movement dynamics of the Taylor’s checkerspot in both suitable habitat and surrounding matrix. Males were highly motile, whereas females appeared sedentary, rarely moving from their natal site. The limited dispersal behavior of females indicates that populations cannot persist naturally in a metapopulation and thus are at high risk of extinction. Based on our findings, we recommend that managers take proactive measures to increase or enable dispersal (including translocation) to existing and/or restored sites.

Wind Turbines do not Negatively Affect Nest Success in the Dickcissel (Spiza americana)

ABSTRACT. Proliferation of wind energy across the Great Plains of the United States has the potential to negatively affect many grassland birds through displacement, avoidance, or changes in nesting ecology. This is troublesome because grassland birds have had the highest average annual rate of decline over the past several decades. We studied the potential indirect effects of wind turbines on nesting success in Dickcissels (Spiza americana) at a utility-scale wind farm in north-central Texas in 2010 and 2011. We monitored 195 nests and found that proximity to a wind turbine did not affect nest density or nest-site characteristics. We used an information-theoretic approach with logistic exposure modeling to identify the most likely models of nest fate. Nest initiation day and distance to wind turbine were the most important predictors of nest success. Proximity to a wind turbine did not reduce nest success. Furthermore, the daily survival rates at our site were within the range documented for Dickcissels at other sites without wind-energy developments. For the monitored nests, snake predation was the greatest source of nest failure and depredated nests were closer to woodland edges than to wind turbines. This may be because wind turbines were farther away from wooded edges. On the other hand, we cannot rule out the possibility that wind-energy development influenced predator behavior and activity, and this may warrant additional investigation. We recommend further research into the breeding ecology of a diverse selection of grassland species to fully assess the indirect effects of wind-energy development on grassland birds.

No evidence of displacement due to wind turbines in breeding grassland songbirds

ABSTRACT Projected global growth in wind energy development has the potential to negatively affect wildlife populations, and yet the indirect effects of wind turbines on wildlife (e.g., displacement from otherwise suitable habitat) remain largely understudied, compared with investigations of direct effects (e.g., collision mortality). Thus, over a 3-yr period (2009–2011), we used 2 alternative survey methods to study displacement in breeding grassland songbirds at an operational wind facility in the southern Great Plains, USA. Using a line transect method in 2009 and 2010, we estimated the densities of Dickcissels (Spiza americana), Eastern Meadowlarks (Sturnella magna), and Grasshopper Sparrows (Ammodramus savannarum) within 500 m of wind turbines. Dickcissel density was positively related to vegetation structure and was highest 301–400 m from wind turbines in both years; however, this relationship was confounded by fence lines bisecting transects within this single distance bin. By contrast, we found no such relationships in Eastern Meadowlarks or Grasshopper Sparrows. Using a plot-based method in 2011, we estimated Dickcissel and Grasshopper Sparrow densities within 750 m of wind turbines. Again, we found a strong positive relationship between Dickcissel density and vegetation structure. With the change in survey method, however, the confounding effect of fence lines was removed and the relationship between distance to turbine and Dickcissel density disappeared. Variation in Grasshopper Sparrow density in 2011 was not explained by any variable we measured. In summary, we found no evidence of displacement within 500–750 m of wind turbines in the 3 most abundant breeding grassland songbirds at our site. We caution that it may be difficult to isolate the effect of distance to turbine from other factors that covary with distance (e.g., presence of fence lines) when using a line transect method to study displacement at operational wind facilities.

Mercury contamination in bats from the central United States

Mercury (Hg) is a highly toxic metal that has detrimental effects on wildlife. We surveyed Hg concentrations in 10 species of bats collected at wind farms in the central United States and found contamination in all species. Mercury concentration in fur was highly variable both within and between species (range: 1.08-10.52 µg/g). Despite the distance between sites (up to 1200 km), only 2 of the 5 species sampled at multiple locations had fur Hg concentrations that differed between sites. Mercury concentrations observed in the present study all fell within the previously reported ranges for bats collected from the northeastern United States and Canada, although many of the bats we sampled had lower maximum Hg concentrations. Juvenile bats had lower concentrations of Hg in fur compared with adult bats, and we found no significant effect of sex on Hg concentrations in fur. For a subset of 2 species, we also measured Hg concentration in muscle tissue; concentrations were much higher in fur than in muscle, and Hg concentrations in the 2 tissue types were weakly correlated. Abundant wind farms and ongoing postconstruction fatality surveys offer an underutilized opportunity to obtain tissue samples that can be used to assess Hg contamination in bats. Environ Toxicol Chem 2018;37:160-165.

Effect of Wind Turbine Proximity on Nesting Success in Shrub-nesting Birds

Abstract Wind energy development is rapidly expanding globally, as are concerns about the potential threats wind facilities pose to bird and bat populations. To date, many studies have explored the direct impacts of wind turbines on wildlife, such as wildlife-turbine collisions, but few have addressed indirect impacts, such as habitat degradation. These potentially subtle impacts can have far reaching effects on the abundance, distribution, survival, and breeding success of wildlife. We conducted a study to assess whether proximity of wind turbines to shrub-nesting birds influenced rates of nest failure associated mainly with depredation and brood parasitism by Brown-headed Cowbirds (Molothrus ater). During the primary nesting period of five passerine species, we monitored 253 active nests. We used a logistic-exposure method to model nest fate as a function of the important variables identified (including distance from turbine and brood parasitism). Our results indicate little relation between nest success and distance to turbine, with one exception, the Blue-gray Gnatcatcher (Polioptila caerule). For this passerine, we found nests closer to wind turbines had a lower probability of being brood parasitized and subsequently had higher nest success rates. We recommend future studies explore the potential implications of wind energy development on brood parasites, such as the Brown-headed Cowbird. As there is regulatory and social pressure to devise management strategies that reduce the impact of brood parasites on species of concern, any opportunities to decrease the risk of brood parasitism could be of benefit.

A method for PCR-based identification of bat species from fecal samples

As bat populations are threatened by a range of factors, there is an increasing need to correctly identify and quantify the cumulative impacts of such factors to individual species. We have developed a fast and reliable method using the polymerase chain reaction to identify bat species from feces found near wind turbines at a north Texas wind farm. The primer sets we developed for the six species found at this site represent an efficient and cost-effective means of obtaining species information from fecal samples. Our approach could readily be applied to other species groups and applications (e.g., degraded carcasses recovered from hibernacula).

Influence of thermal conditions on habitat use by a rare spring-emerging butterfly Euphydryas editha taylori

We may expect butterflies as ectotherms to have particularly active life‐history stages that occur in the warmest and lightest times of the year; however, there are temperate species that are active when climatic conditions seem unfavourable and photoperiod short, such as the Taylors checkerspot (Euphydryas editha taylori). For such species, studies suggest that even subtle changes to microclimate can potentially impact populations. Thus, understanding how in situ variations in microclimate influence the Taylors checkerspot butterfly could provide much needed insights into more effective management. We conducted a series of surveys that explored (i) adult habitat use, (ii) final instar larval distribution and (iii) adult movement up to and across site boundaries at two sites in Oregon, USA, in 2010 and 2011. We found that in situ habitat use by the Taylors checkerspot butterfly was strongly influenced by microclimate. Both adult activities and final instar larvae distribution were clustered within the warmest areas of the sites. Moreover, adults did not use up to 59% and larva up to 90% of their sites, despite vegetation structure and composition being uniform. More specifically, butterfly habitat use increased with increasing ground temperatures, and we found that areas with the highest ground temperatures were more exposed to direct sunlight. Similarly, we found that butterflies tended to only move through sunlit site boundaries. We conclude that the Taylors checkerspot is sensitive to changes in its thermal environment at fine spatial scales. Our results highlight the importance of microclimate as an indicator of habitat quality, and establishing the thermal criteria in which species of concern exists may provide valuable insights into the implications of climate change.

Increasing evidence that bats actively forage at wind turbines

Although the ultimate causes of high bat fatalities at wind farms are not well understood, several lines of evidence suggest that bats are attracted to wind turbines. One hypothesis is that bats would be attracted to turbines as a foraging resource if the insects that bats prey upon are commonly present on and around the turbine towers. To investigate the role that foraging activity may play in bat fatalities, we conducted a series of surveys at a wind farm in the southern Great Plains of the US from 2011–2016. From acoustic monitoring we recorded foraging activity, including feeding buzzes indicative of prey capture, in the immediate vicinity of turbine towers from all six bat species known to be present at this site. From insect surveys we found Lepidoptera, Coleoptera, and Orthoptera in consistently high proportions over several years suggesting that food resources for bats were consistently available at wind turbines. We used DNA barcoding techniques to assess bat diet composition of (1) stomach contents from 47 eastern red bat (Lasiurus borealis) and 24 hoary bat (Lasiurus cinereus) carcasses collected in fatality searches, and (2) fecal pellets from 23 eastern red bats that were found on turbine towers, transformers, and tower doors. We found that the majority of the eastern red bat and hoary bat stomachs, the two bat species most commonly found in fatality searches at this site, were full or partially full, indicating that the bats were likely killed while foraging. Although Lepidoptera and Orthoptera dominated the diets of these two bat species, both consumed a range of prey items with individual bats having from one to six insect species in their stomachs at the time of death. The prey items identified from eastern red bat fecal pellets showed similar results. A comparison of the turbine insect community to the diet analysis results revealed that the most abundant insects at wind turbines, including terrestrial insects such as crickets and several important crop pests, were also commonly eaten by eastern red and hoary bats. Collectively, these findings suggest that bats are actively foraging around wind turbines and that measures to minimize bat fatalities should be broadly implemented at wind facilities.