Lasiurus Cinereus Research Articles

The relative influence of forest loss and fragmentation on insectivorous bats: does the type of matrix matter?

Context Disentangling the relative effects of forest loss versus fragmentation on species distribution and abundance iscrucial for adopting efficient biodiversity conservation actions, which could change with the nature of the landscape matrix. Objectives We tested the moderating effect of landscape matrix on insectivorous bats response to forest loss and fragmentation. Methods We conducted acoustic surveys at forest patches surrounded by either an agricultural-dominated matrix or a pine-dominated matrix. We related bat activity to forest amount and the number of forest patches at multiple spatial scales, and compared their effects between landscape matrices. Results Bat activity was associated with both predictors, however their effects varied with the matrix type. In agricultural landscapes, as the amount of forest increased, the activity of Histiotus montanus, Lasiurus cinereus and Tadarida brasiliensis increased, while activity of Myotis chiloensis decreased. Similarly, as fragmentation increased, the activity of Lasiurus varius and M. chiloensis increased, while activity of H. montanus decreased. In productionforest landscapes, only H. montanus decreased its activity with increasing forest amount. In contrast, activity of L. cinereus, M. chiloensis and T. brasiliensis increased with increasing fragmentation. Forest amount was a stronger predictor for agricultural landscapes than for production-forest landscapes, suggesting that low contrast matrices can mitigate the effects of forest loss. Conclusions Fragmented landscapes with native forest patches surrounded by a low contrast matrix may support a higher activity of insectivorous bats. Management efforts in fragmented landscapes should aim to decrease the patch-matrix contrast, which will mitigate the effects of forest loss on bats.

Three new host species of Plagiorchis micracanthos (Macy, 1931) (Trematodes: Plagorchiidae) among North American bats (Chiroptera: Vespertilionidae)

Summary We report new records of the trematode, Plagiorchis micracanthos from three North American bats. For the first time, the parasite is reported to occur in the hoary bat (Lasiurus cinereus), California myotis (Myotis californicus) and the pallid bat (Antrozous pallidus). The western small-footed bat (Myotis ciliolabrum), little brown bat (M. lucifugus) and the western pipistrelle (Parastellus hesperus) are confirmed as host species. The trematodes were isolated from the small intestines of the host individuals. For the first time, we identified P. micracanthos in bats originating from Canada and Mexico. The results presented here suggest that the trematode P. micracanthos has a much larger host range and geographic distribution than previously recognised. It is likely that further studies will confirm this results and extent both host and geographic ranges even further.

Foraging range movements of the endangered Hawaiian hoary bat,Lasiurus cinereus semotus(Chiroptera: Vespertilionidae)

We documented nightly movements of Hawaiian hoary bats (Lasiurus cinereus semotus) on the island of Hawai'i. Based on data from 28 radiotagged individuals mean foraging range (FR) was 230.7 ± 72.3 ha, core-use area (CUA) was 25.5 ± 6.9 ha (or 11.1% of mean FR), and the mean long axis (LAX) across the FR was 3,390.8 ± 754.3 m. There was almost no overlap in CUAs among 4 adult males having overlapping foraging areas and tracked simultaneously or within a 90-day window of each other. CUAs of subadults partially overlapped with multiple adult males or with one other subadult. High variance in FRs, cores use areas, and LAX across the FR perhaps reflect localized stochastic variables such as weather, habitat, and food resources. Hawaiian hoary bats use moderately large FRs among insectivorous bats studied with comparable methodologies; however, foraging activity indicated by documentation of acoustic feeding buzzes is concentrated within one or a few disjunct areas cumulatively forming the 50% fixed kernel of C...

Species composition and mortality of bats at the Osório Wind Farm, southern Brazil

We present the results of a three-year study on the bat species killed by wind turbines at the Osório Wind Farm, a large wind power complex in southern Brazil, and compare these fatalities to the composition of the local bat fauna. Fatality searches around wind turbines were conducted from 2006 to 2009, as well as a bat inventory through mist-netting and searches for colonies from 2004 to 2010. We found a total of 336 bat fatalities: Tadarida brasiliensis (n = 245), Lasiurus cinereus (n = 44), Nyctinomops laticaudatus (n = 12), Molossus molossus (n = 9), Lasiurus blossevillii (n = 6), Promops nasutus (n = 3), Lasiurus ega (n = 3), Molossus rufus (n = 1), and Artibeus lituratus (n = 1). By mist-netting, we recorded 13 bat species in the region, of which only six were killed by wind turbines. Our results are similar to mortality patterns from the Northern Hemisphere in terms of: (1) uneven distribution of fatalities among species; (2) dominance of migratory species, including foliage/tree-roosting bats; and (3) discrepancy between presence and abundance of species recorded in the wind farm area and in the fatality sample.

Not to Put Too Fine a Point on It — Does Increasing Precision of Geographic Referencing Improve Species Distribution Models for a Wide-Ranging Migratory Bat?

Bat specimens held in natural history museum collections can provide insights into the distribution of species. However, there are several important sources of spatial error associated with natural history specimens that may influence the analysis and mapping of bat species distributions. We analyzed the importance of geographic referencing and error correction in species distribution modeling (SDM) using occurrence records of hoary bats (Lasiurus cinereus). This species is known to migrate long distances and is a species of increasing concern due to fatalities documented at wind energy facilities in North America. We used 3,215 museum occurrence records collected from 1950–2000 for hoary bats in North America. We compared SDM performance using five approaches: generalized linear models, multivariate adaptive regression splines, boosted regression trees, random forest, and maximum entropy models. We evaluated results using three SDM performance metrics (AUC, sensitivity, and specificity) and two data sets: one comprised of the original occurrence data, and a second data set consisting of these same records after the locations were adjusted to correct for identifiable spatial errors. The increase in precision improved the mean estimated spatial error associated with hoary bat records from 5.11 km to 1.58 km, and this reduction in error resulted in a slight increase in all three SDM performance metrics. These results provide insights into the importance of geographic referencing and the value of correcting spatial errors in modeling the distribution of a wide-ranging bat species. We conclude that the considerable time and effort invested in carefully increasing the precision of the occurrence locations in this data set was not worth the marginal gains in improved SDM performance, and it seems likely that gains would be similar for other bat species that range across large areas of the continent, migrate, and are habitat generalists.

Dim ultraviolet light as a means of deterring activity by the Hawaiian hoary bat Lasiurus cinereus semotus

Widespread bat fatalities at industrial wind turbines are a conservation issue with the potential to inhibit efficient use of an abundant source of energy. Bat fatalities can be reduced by altering turbine operations, but such curtailment decreases turbine efficiency. If additional ways of reducing bat fatalities at wind turbines were available such tradeoffs might not be needed. Based on the facts that bats perceive distant objects primarily through vision and can see in very dim lighting conditions, and the possibility that bats might interact with turbines after approach- ing them as they would trees, we propose a novel method of reducing bat activity at wind turbines: illumination of the structure with dim light. As a first step toward assessing this approach, we illu- minated trees with dim flickering ultraviolet (UV) light in areas frequented by Hawaiian hoary bats Lasiurus cinereus semotus, an endangered subspecies affected by wind turbines. We used a repeated-measures design to quantify bat activity near trees with acoustic detectors and thermal video cameras in the presence and absence of UV illumination, while concurrently monitoring insect numbers. Results indicate that dim UV reduces bat activity despite an increase in insect numbers. Experimental treatment did not completely inhibit bat activity near trees, nor did all measures of bat activity show statistically significant differences due to high variance in bat activ- ity among sites. However, the observed decreases in bat activity with dim UV illumination justify further testing of this method as a means to reduce bat fatalities at wind turbines.

Bat survey of Griffith Park, Los Angeles, California

Griffith Park in Los Angeles is notable for its high ecological integrity within a highly urbanized region. We present results of a 2008 bat survey conducted in the park that confirmed seven bat species, and discuss an additional three species that have been recorded incidentally nearby. On the basis of our research, the Griffith Park bat community is notable for the abundance of the canyon bat (Parastrellus hesperus), for a population of the hoary bat (Lasiurus cinereus), and for the relatively minor representation of urban-adapted bats, considering its location.

Origins and migratory patterns of bats killed by wind turbines in southern Alberta: evidence from stable isotopes

Large numbers of migratory bats are killed every autumn at wind energy facilities in North America. While this may be troubling from a population perspective, these fatalities provide an opportunity to learn more about bat migration and the origins and summer distributions of migratory bats by using endogenous markers. Such markers include stable isotope values, which have been used to answer questions about ecological systems, such as trophic levels and food webs, and the origins and migratory routes of animals. To estimate the origins of migratory bats, we determined nitrogen (δ15N), carbon (δ13C), and hydrogen (δ2H) stable isotope values of fur (δ15Nf, δ13Cf, δ2Hf,respectively) from hoary bats (Lasiurus cinereus) and silver‐haired bats (Lasionycteris noctivagans) killed at a wind energy facility in southern Alberta, Canada. We determined that mean isotope values varied among species, year, sex, and age class. δ13Cfand δ2Hfvalues indicated that silver‐haired bats likely originated in the boreal forest, farther north and/or at higher elevations than the aspen parkland‐like habitat suggested by the isotope values of hoary bats. IsoMAP analysis indicated that bat fatalities may have originated from a large catchment area potentially hundreds of kilometers away. Our data provide further evidence for a migration route along the eastern slopes of the Rocky Mountains that is used by bats from across Alberta and beyond, and suggest that fatalities at a single wind energy site have the potential to have far‐reaching ecological and population consequences.

Activity and diet of bats in conventional versus organic apple orchards in southern Michigan

Organic farming practices have been suggested as a conservation strategy that can provide productive foraging sites for insectivorous bats in agricultural areas. We tested the hypothesis that the number and diversity of insects captured and the resulting activity and diet of bats would differ between organic and conventional apple orchards. During the summer of 2009 and 2010, we captured 131 Big Brown Bats (Eptesicus fuscus) and five Eastern Red Bats (Lasiurus borealis) by mist netting in four organic and four conventional orchards in Michigan. Acoustic monitoring revealed that most calls (59%) were produced by Big Brown Bats, followed by Hoary Bats (L. cinereus), Eastern Red Bats, and unidentified species of Myotis. Most insects (96%) captured in light traps were Coleoptera, Diptera, Hemiptera, Lepidoptera, and Trichoptera; fecal analysis indicated that Coleoptera dominated the diet of Big Brown Bats (79% by volume), followed by Diptera (14%). There were no significant differences between organic and conventional orchards in number of insects captured with light traps, bats captured with mist nets, acoustic recordings of bats, or proportion of Coleoptera and Diptera consumed by the bats. However, the taxonomic composition of captured insects and acoustic recordings was not homogenous among orchards in either group, suggesting that factors other than farming practices were more important in determining which insects and bats were found in the small orchards typical of southern Michigan.

Structure and Reproductive Patterns in the Summertime Forest-Bat Community of Southeastern Texas

Abstract Forests of eastern Texas represent the westernmost extent of the southern pine forests and part of the pine belt of the forested Gulf coastal plain. Bat community assemblages in similar forests throughout southeastern United States have been documented in various studies, but only scant data are available for Texas. The purpose of this study was to characterize the assemblage and investigate reproductive patterns of the summer bat community in the austroriparian forest of eastern Texas. Using mist nets, we captured bats during summers 2009–2011 and recorded species, gender, age and reproductive condition. We captured 382 bats of eight species: Seminole Lasiurus seminolus (n = 163), evening Nycticeius humeralis (n = 86), big brown Eptesicus fuscus (n = 57), eastern red Lasiurus borealis (n = 31), southeastern myotis Myotis austroriparius (n = 21), tri-colored Perimyotis subflavus (n = 19), Mexican free-tailed Tadarida brasiliensis (n = 4), and hoary Lasiurus cinereus (n = 1) bats. Analysis of reproductive data suggests that three of these species (big brown, evening, and Seminole bats) may be following a reproductive strategy—extended seasonal monoestry (births of single litters spanning a particular season)—different than their previously reported pattern of synchronous monoestry.

Continental-scale, seasonal movements of a heterothermic migratory tree bat.

Long-distance migration evolved independently in bats and unique migration behaviors are likely, but because of their cryptic lifestyles, many details remain unknown. North American hoary bats (Lasiurus cinereus cinereus) roost in trees year-round and probably migrate farther than any other bats, yet we still lack basic information about their migration patterns and wintering locations or strategies. This information is needed to better understand unprecedented fatality of hoary bats at wind turbines during autumn migration and to determine whether the species could be susceptible to an emerging disease affecting hibernating bats. Our aim was to infer probable seasonal movements of individual hoary bats to better understand their migration and seasonal distribution in North America. We analyzed the stable isotope values of non-exchangeable hydrogen in the keratin of bat hair and combined isotopic results with prior distributional information to derive relative probability density surfaces for the geographic origins of individuals. We then mapped probable directions and distances of seasonal movement. Results indicate that hoary bats summer across broad areas. In addition to assumed latitudinal migration, we uncovered evidence of longitudinal movement by hoary bats from inland summering grounds to coastal regions during autumn and winter. Coastal regions with nonfreezing temperatures may be important wintering areas for hoary bats. Hoary bats migrating through any particular area, such as a wind turbine facility in autumn, are likely to have originated from a broad expanse of summering grounds from which they have traveled in no recognizable order. Better characterizing migration patterns and wintering behaviors of hoary bats sheds light on the evolution of migration and provides context for conserving these migrants.

Large roads reduce bat activity across multiple species.

Although the negative impacts of roads on many terrestrial vertebrate and bird populations are well documented, there have been few studies of the road ecology of bats. To examine the effects of large roads on bat populations, we used acoustic recorders to survey bat activity along ten 300 m transects bordering three large highways in northern California, applying a newly developed statistical classifier to identify recorded calls to the species level. Nightly counts of bat passes were analyzed with generalized linear mixed models to determine the relationship between bat activity and distance from a road. Total bat activity recorded at points adjacent to roads was found to be approximately one-half the level observed at 300 m. Statistically significant road effects were also found for the Brazilian free-tailed bat (Tadarida brasiliensis), big brown bat (Eptesicus fuscus), hoary bat (Lasiurus cinereus), and silver-haired bat (Lasionycteris noctivagans). The road effect was found to be temperature dependent, with hot days both increasing total activity at night and reducing the difference between activity levels near and far from roads. These results suggest that the environmental impacts of road construction may include degradation of bat habitat and that mitigation activities for this habitat loss may be necessary to protect bat populations.

A Comparison of Passive and Active Acoustic Sampling for a Bat Community Impacted by White-Nose Syndrome

Abstract In the summers of 2011 and 2012, we compared passive and active acoustic sampling for bats at 31 sites at Fort Drum Military Installation, New York. We defined active sampling as acoustic sampling that occurred in 30-min intervals between the hours of sunset and 0200 with a user present to manipulate the directionality of the microphone. We defined passive sampling as acoustic sampling that occurred over a 12-h period (1900–0700 hours) without a user present and with the microphone set in a predetermined direction. We detected seven of the nine possible species at Fort Drum, including the federally endangered Indiana bat Myotis sodalis, the proposed-for-listing northern bat M. septentrionalis, the little brown bat M. lucifugus, and the big brown bat Eptesicus fuscus, which are impacted by white-nose syndrome (WNS); and the eastern red bat Lasiurus borealis, the hoary bat L. cinereus, and the silver-haired bat Lasionycteris noctivagans, which are not known to be impacted by WNS. We did not detect two additional WNS-impacted species known to historically occur in the area: the eastern small-footed bat Myotis leibii and the tri-colored bat Perimyotis subflavus. Single-season occupancy models revealed lower detection probabilities of all detected species using active sampling versus passive sampling. Additionally, overall detection probabilities declined in detected WNS-impacted species between years. A paired t-test of simultaneous sampling on 21 occasions revealed that overall recorded foraging activity per hour was greater using active than passive sampling for big brown bats and greater using passive than active sampling for little brown bats. There was no significant difference in recorded activity between methods for other WNS-impacted species, presumably because these species have been so reduced in number that their “apparency” on the landscape is lower. Finally, a cost analysis of standard passive and active sampling protocols revealed that passive sampling is substantially more cost-effective than active sampling per hour of data collection. We recommend passive sampling over active sampling methodologies as they are defined in our study for detection probability and/or occupancy studies focused on declining bat species in areas that have experienced severe WNS-associated impacts.

Avascularity in the cortical bone of small bats as revealed by micro computed tomography (920.3)

The spatial distribution of vascular canals in cortical bone reflects the mechanical loading conditions present during the formation of the bone. In the flight bones of birds, these canals have a laminar pattern, oriented circumferentially around the medullary cavity. Evidence for this pattern and its relation to torsional loading has thus far come from histological studies, however vascular canals exist in 3D and their cross sections in a 2D slice may vary from their actual 3D morphology. We hypothesized that bats would show the same laminar pattern in their flight bones and that high resolution 3D imaging would better reveal the extent of the cortical network. We used micro‐computed tomography (micro‐CT) to examine the cortical network of two species of bats (Eptesicus fuscus pallidus, Lasiurus cinereus), two species of birds (Tyrannus verticalis, Seiurus aurocapillus), and two species of terrestrial mammals (Mus musculus, Eutamias minimus), all of similar size. Contrary to our expectations we found that the bats had cortices devoid of vascular canals. Compared to the terrestrial mammals, we found that the birds had a reduction in the number of cortical vascular canals present and did not exhibit the anticipated laminar pattern found previously in larger bird species.

Potential citric acid exposure and toxicity to Hawaiian hoary bats (Lasiurus cinereus semotus) associated with Eleutherodactylus frog control

We examined potential exposure of Hawaiian hoary bats (Lasiurus cinereus semotus) to citric acid, a minimum risk pesticide registered for control of invasive Eleutherodactylus frog populations. Hoary bats are nocturnal insectivores that roost solitarily in foliage, federally listed as endangered, and are endemic to Hawaii. Oral ingestion during grooming of contaminated fur appears to be the principal route by which these bats might be exposed to citric acid. We made assessments of oral toxicity, citric acid consumption, retention of material on fur, and grooming using big brown bats (Eptesicus fuscus) as a surrogate species. We evaluated both ground application and aerial application of 16 % solutions of citric acid during frog control operations. Absorbent bat effigies exposed to ground and aerial operational spray applications retained means of 1.54 and 0.02 g, respectively, of dry citric acid, although retention by the effigies was much higher than bat carcasses drenched in citric acid solutions. A high dose delivered orally (2,811 mg/kg) was toxic to the big brown bats and emesis occurred in 1 bat dosed as low as the 759 mg/kg level. No effect was observed with the lower doses examined (≤ 542 mg/kg). Bats sprayed with 5 ml of 16 % (w/w) citric acid solution showed no evidence of intoxication. In field situations, it is unlikely that bats would be sprayed directly or ingest much citric acid retained by fur. Based on our observations, we believe Hawaiian hoary bats to be at very low risk from harmful exposure to a toxic dose of citric acid during frog control operations.

Flight muscle carnitine palmitoyl transferase activity varies with substrate chain length and unsaturation in the hoary bat (Lasiurus cinereus)

Fat is an important fuel for bats to support high metabolic rates in extended periods of flight. The fatty acid composition of adipose stores could affect whole animal exercise performance, as fatty acids vary in rates of mobilization and oxidation. A key step in the fatty acid oxidation pathway is transporting fatty acids from the cytosol into mitochondria, mediated by the enzyme carnitine palmitoyl transferase (CPT). Therefore, understanding the substrate preference patterns of CPT in bats is important for interpreting the consequences of adipose fatty acid profiles. We measured CPT activity with eight different fatty acyl CoA substrates (16:0, 16:1ω7, 18:0, 18:1ω9, 18:2ω6, 18:3ω3, 20:4ω6, and 22:6ω3) in the pectoralis muscle of migrating and nonmigrating hoary bats (Lasiurus cinereus (Beauvois, 1796)). The pattern of substrate preference was similar to the patterns previously reported for birds and rats and was not affected by migration. Generally, activity increased with the number of double bonds and was higher with 16 carbon fatty acids compared with 18 carbon fatty acids. Given the observed substrate variation in CPT activity, there is no evidence to suggest that recently reported seasonal changes in the adipose fatty acid composition of migrating hoary bats would lead to increased lipid oxidation rate, and may instead be a consequence of seasonal shifts in diet.

Development and characterization of microsatellite loci for eastern red and hoary bats (Lasiurus borealis and L. cinereus)

We developed ten dinucleotide and four tetranucleotide microsatellite markers for two species of tree bats from the family Vespertilionidae that are experiencing high mortality at wind energy facilities. Eleven of these loci were polymorphic in eastern red bats (Lasiurus borealis), whereas nine loci were polymorphic in hoary bats (Lasiurus cinereus). The number of alleles per locus ranged from 2 to 29 (mean = 14 alleles) and observed heterozygosity was generally high (mean 0.754, range 0.125–0.979). This set of microsatellite markers will be useful for studying population structure of these bats as part of a larger effort to understand the potential impacts of wind energy development on their populations.

Acoustic Monitoring Provides First Records of Hoary Bats (Lasiurus cinereus) and Delineates the Distribution of Silver-Haired Bats (Lasionycteris noctivagans) in Southeast Alaska

Although 5 species of bats have been documented in Southeast Alaska, information on species not of the genus Myotis is derived solely from 4 specimens of the Silver-haired Bat (Lasionycteris noctivagans). We acoustically monitored for bat species that produce low frequency echolocation calls (<30 kHz minimum frequency), specifically Hoary Bat (Lasiurus cinereus), Silver-haired Bat, and Big Brown Bat (Eptesicus fuscus) at 40 sites in 16 locations across Southeast Alaska from 2011 to 2013 using passive bat detectors. The Hoary Bat was not previously known from Alaska, but we recorded 25 call files of this species (of 26,151 low frequency bat files) at 5 sites in northern Southeast Alaska (4 mainland sites and 1 site on Chichagof Island); an additional 110 call files were classified as probable Hoary Bat, but were ambiguous. We recorded 3075 call files that contained echolocation calls diagnostic of Silver-haired Bats; no files had characteristics diagnostic of Big Brown Bats. The rest of the low frequency recordings were identified as probable Silver-haired Bat calls, although Big Brown Bats cannot be ruled out due to the extensive overlap of acoustic characteristics between these 2 species. We recorded Hoary Bats almost exclusively during the autumn migration period. By contrast, Silver-haired Bats were detected throughout the summer active season, indicating at least some individuals are resident in Southeast Alaska. Silver-haired Bat activity was greatest at sites on or near the mainland, with most sites showing peaks of activity in spring, suggesting bats from the interior may be overwintering in the region. Winter recordings suggest Silver-haired Bats (and Big Brown Bats if present) are active to some extent during winter in Southeast Alaska. Understanding the distribution and seasonality of Hoary and Silver-haired Bat activity in Southeast Alaska is a critical 1st step toward identifying their habitat requirements and conservation needs in this region.

Diversity and Distribution of Bats in the Northwest Territories

The occurrence of bats at the northern limit of their ranges in the Northwest Territories (NT), Canada, is not well documented. We provide information on the diversity and distribution of bat species in the NT by synthesizing available records. Before 2006, only 3 species of bats were known to occur in the NT: Little Brown Myotis (Myotis lucifugus), Northern Myotis (M. septentrionalis), and Hoary Bat (Lasiurus cinereus). Focused bat surveys as well as observations of bats reported by residents have added Long-eared Myotis (M. evotis), Long-legged Myotis (M. volans), Big Brown Bat (Eptesicus fuscus), and Silver-haired Bat (Lasionycteris noctivagans), for a total of 7 confirmed species, plus an additional species that is unconfirmed but suspected to occur (Eastern Red Bat, Lasiurus borealis). Range extensions for Little Brown Myotis, Hoary Bat, and Silver-haired Bat are reported. Both Little Brown Myotis and Northern Myotis are reproducing in the NT and are likely abundant in southern NT. Little Brown Myotis has been confirmed to overwinter in the NT and the northern limit of bat hibernation may be further north than previously supposed. Bats are widespread in the southern Central Plains region and gaps in occurrences likely reflect gaps in search effort. Nahanni National Park Reserve has high bat diversity and other parts of southwestern NT are suspected to have similarly high diversity, but have not yet been surveyed. There is evidence that the Eastern Shield region supports bats at relatively low densities. The northern distribution limit of bats in the NT is not known but is expected to occur in the Mackenzie Valley north of 62°N.

Pre-Construction Bat Activity At Four Wind Energy Sites in Northeastern British Columbia

We monitored pre-construction bat acoustic activity from 2007 to 2010 at 4 wind energy sites in northeastern British Columbia to determine nightly and seasonal activity patterns, relative detection rates of different species groups, and the implications for potential fatalities at northern wind facilities. Mean activity rates (August to September) ranged from 2.4 to 79.4 passes per detector-night at the 4 study areas. Activity differed between years for 3 study areas with multi-year data. Nightly variation in activity was pronounced, with wind speed and temperature recorded at meteorological towers explaining 47 to 61% of the variation in nightly activity. Detections were predominantly (60 to 96%) of Myotis bats. Only 1 to 18% of passes recorded at study areas were low-frequency bats (Big Brown Bat, Eptesicus fuscus; Silver-haired Bat, Lasionycteris noctivagans; Hoary Bat, Lasiurus cinereus), with L. cinereus accounting for <1% of the low-frequency passes. No Eastern Red Bats (Lasiurus borealis) were detected. Seasonal activity of low-frequency bats showed no evidence of an influx of spring migrants, but single-night activity spikes in late August and early September were suggestive of autumn migration. Activity of Myotis bats was highest in August and early September, a pattern consistent with resident populations. Results suggest that Myotis species may form a larger proportion of fatalities at northern wind energy facilities than at sites in more temperate regions.