Joseph M. Szewczak

Assessing Impacts of Wind-Energy Development on Nocturnally Active Birds and Bats: A Guidance Document

Abstract Our purpose is to provide researchers, consultants, decision-makers, and other stakeholders with guidance to methods and metrics for investigating nocturnally active birds and bats in relation to utility-scale wind-energy development. The primary objectives of such studies are to 1) assess potential impacts on resident and migratory species, 2) quantify fatality rates on resident and migratory populations, 3) determine the causes of bird and bat fatalities, and 4) develop, assess, and implement methods for reducing risks to bird and bat populations and their habitats. We describe methods and tools and their uses, discuss limitations, assumptions, and data interpretation, present case studies and examples, and offer suggestions for improving studies on nocturnally active birds and bats in relation to wind-energy development. We suggest best practices for research and monitoring studies using selected methods and metrics, but this is not intended as cookbook. We caution that each proposed and executed study will be different, and that decisions about which methods and metrics to use will depend upon several considerations, including study objectives, expected and realized risks to bird and bat populations, as well as budgetary and logistical considerations. Developed to complement and extend the existing National Wind Coordinating Committee document “Methods and Metrics for Assessing Impacts of Wind Energy Facilities on Wildlife” (Anderson et al. 1999), we provide information that stakeholders can use to aid in evaluating potential and actual impacts of wind power development on nocturnally active birds and bats. We hope that decision-makers will find these guidelines helpful as they assemble information needed to support the permitting process, and that the public will use this guidance document as they participate in the permitting processes. We further hope that the wind industry will find valuable guidance from this document when 1) complying with data requirements as a part of the permitting process, 2) evaluating sites for potential development, 3) assessing impacts of operational wind-energy facilities, and 4) mitigating local and cumulative impacts on nocturnally active birds and bats.

Increased fiber capillarization in flight muscle of finch at altitude.

We examined fiber capillarization and ultrastructure in the highly aerobic flight muscle of six gray crowned rosy finches (Leucosticte arctoa; mass 22.9 +/- 0.5 (SE) g) living at altitude (A; White Mountains of Eastern California; 4000 m) compared to eight sea-level (SL) house finches (Carpodacus mexicanus, mass, 19.8 +/- 0.6 g) of the same subfamily, Carduelinae. Capillary length per fiber volume (A, 10,400 +/- 409 mm(-2); SL, 7513 +/- 423; P < 0.001) and capillary-to-fiber ratio (A, 2.32 +/- 0.07; SL, 1.85 +/- 0.06; P < 0.001) were significantly greater in A, with no difference in fiber cross-sectional area compared to SL. Capillary geometry was significantly different in A, yielding a greater contribution of tortuosity and branching to capillary length than in SL. Capillary-to-fiber surface ratio and fiber mitochondrial volume were both greater in A, but their ratio was similar to SL, indicating a proportional increase in the size of the capillary to fiber interface and fiber mitochondrial volume in A to sustain high levels of aerobic capacity while living at altitude.

Classification of Echolocation Calls from 14 Species of Bat by Support Vector Machines and Ensembles of Neural Networks

Calls from 14 species of bat were classified to genus and species using discriminant function analysis (DFA), support vector machines (SVM) and ensembles of neural networks (ENN). Both SVMs and ENNs outperformed DFA for every species while ENNs (mean identification rate – 97%) consistently outperformed SVMs (mean identification rate – 87%). Correct classification rates produced by the ENNs varied from 91% to 100%; calls from six species were correctly identified with 100% accuracy. Calls from the five species of Myotis, a genus whose species are considered difficult to distinguish acoustically, had correct identification rates that varied from 91 – 100%. Five parameters were most important for classifying calls correctly while seven others contributed little to classification performance.

Evaluating the Effectiveness of an Ultrasonic Acoustic Deterrent for Reducing Bat Fatalities at Wind Turbines

Large numbers of bats are killed by wind turbines worldwide and minimizing fatalities is critically important to bat conservation and acceptance of wind energy development. We implemented a 2-year study testing the effectiveness of an ultrasonic acoustic deterrent for reducing bat fatalities at a wind energy facility in Pennsylvania. We randomly selected control and treatment turbines that were searched daily in summer and fall 2009 and 2010. Estimates of fatality, corrected for field biases, were compared between treatment and control turbines. In 2009, we estimated 21–51% fewer bats were killed per treatment turbine than per control turbine. In 2010, we determined an approximate 9% inherent difference between treatment and control turbines and when factored into our analysis, variation increased and between 2% more and 64% fewer bats were killed per treatment turbine relative to control turbines. We estimated twice as many hoary bats were killed per control turbine than treatment turbine, and nearly twice as many silver-haired bats in 2009. In 2010, although we estimated nearly twice as many hoary bats and nearly 4 times as many silver-haired bats killed per control turbine than at treatment turbines during the treatment period, these only represented an approximate 20% increase in fatality relative to the pre-treatment period for these species when accounting for inherent differences between turbine sets. Our findings suggest broadband ultrasound broadcasts may reduce bat fatalities by discouraging bats from approaching sound sources. However, effectiveness of ultrasonic deterrents is limited by distance and area ultrasound can be broadcast, in part due to rapid attenuation in humid conditions. We caution that an operational deterrent device is not yet available and further modifications and experimentation are needed. Future efforts must also evaluate cost-effectiveness of deterrents in relation to curtailment strategies to allow a cost-benefit analysis for mitigating bat fatalities.

Assessing the status and trend of bat populations across broad geographic regions with dynamic distribution models

Bats face unprecedented threats from habitat loss, climate change, disease, and wind power development, and populations of many species are in decline. A better ability to quantify bat population status and trend is urgently needed in order to develop effective conservation strategies. We used a Bayesian autoregressive approach to develop dynamic distribution models for Myotis lucifugus, the little brown bat, across a large portion of northwestern USA, using a four-year detection history matrix obtained from a regional monitoring program. This widespread and abundant species has experienced precipitous local population declines in northeastern USA resulting from the novel disease white-nose syndrome, and is facing likely range-wide declines. Our models were temporally dynamic and accounted for imperfect detection. Drawing on species-energy theory, we included measures of net primary productivity (NPP) and forest cover in models, predicting that M. lucifugus occurrence probabilities would covary positively along those gradients. Despite its common status, M. lucifugus was only detected during -50% of the surveys in occupied sample units. The overall naive estimate for the proportion of the study region occupied by the species was 0.69, but after accounting for imperfect detection, this increased to -0.90. Our models provide evidence of an association between NPP and forest cover and M. lucifugus distribution, with implications for the projected effects of accelerated climate change in the region, which include net aridification as snowpack and stream flows decline. Annual turnover, the probability that an occupied sample unit was a newly occupied one, was estimated to be low (-0.04-0.14), resulting in flat trend estimated with relatively high precision (SD = 0.04). We mapped the variation in predicted occurrence probabilities and corresponding prediction uncertainty along the productivity gradient. Our results provide a much needed baseline against which future anticipated declines in M. lucifugus occurrence can be measured. The dynamic distribution modeling approach has broad applicability to regional bat monitoring efforts now underway in several countries and we suggest ways to improve and expand our grid-based monitoring program to gain robust insights into bat population status and trend across large portions of North America.

Accounting for false-positive acoustic detections of bats using occupancy models

Summary 1. Acoustic surveys have become a common survey method for bats and other vocal taxa. Previous work shows that bat echolocation may be misidentified, but common analytic methods, such as occupancy models, assume that misidentifications do not occur. Unless rare, such misidentifications could lead to incorrect inferences with significant management implications. 2. We fit a false-positive occupancy model to data from paired bat detector and mist-net surveys to estimate probability of presence when survey data may include false positives. We compared estimated occupancy and detection rates to those obtained from a standard occupancy model. We also derived a formula to estimate the probability that bats were present at a site given its detection history. As an example, we analysed survey data for little brown bats Myotis lucifugus from 135 sites in Washington and Oregon, USA. 3. We estimated that at an unoccupied site, acoustic surveys had a 14% chance per night of producing spurious M. lucifugus detections. Estimated detection rates were higher and occupancy rates were lower under the false-positive model, relative to a standard occupancy model. Un-modelled false positives also affected inferences about occupancy at individual sites. For example, probability of occupancy at individual sites with acoustic detections but no captures ranged from 2% to 100% under the false-positive occupancy model, but was always 100% under a standard occupancy model. 4. Synthesis and applications. Our results suggest that false positives sufficient to affect inferences may be common in acoustic surveys for bats. We demonstrate an approach that can estimate occupancy, regardless of the false-positive rate, when acoustic surveys are paired with capture surveys. Applications of this approach include monitoring the spread of WhiteNose Syndrome, estimating the impact of climate change and informing conservation listing decisions. We calculate a site-specific probability of occupancy, conditional on survey results, which could inform local permitting decisions, such as for wind energy projects. More generally, the magnitude of false positives suggests that false-positive occupancy models can improve accuracy in research and monitoring of bats and provide wildlife managers with more reliable information.

Vocal Individuality of Great Gray Owls in the Sierra Nevada

Abstract The cryptic plumage and nocturnal nature of the great gray owl (Strix nebulosa) make it difficult to study in its densely forested habitat. We investigated whether the vocalizations of individual great gray owls could be distinguished and used as a tool for population survey and monitoring. We recorded 312 territorial calls produced by 14 male and 11 female great gray owls between March and July 2006 and 2007 in the Sierra Nevada range of California, USA. We recorded 19 owls on multiple occasions within a season and 8 owls between seasons. We extracted 17 frequency and 15 temporal variables from the sonograms of each call. Discriminant analysis selected 9 variables and classified 92.8% of calls to the correct individual within a season; 71.4% of calls were classified to the correct individual between seasons. Our results indicate that territorial calls could be used to monitor individual great gray owls for both short- and long-term studies. Vocal individuality could be useful as a noninvasive method to improve census estimates and yield information on site fidelity, turnover rates, seasonal movements, and behavioral traits of great gray owls.

Ventilatory response to hypoxia and hypercapnia in the torpid bat, Eptesicus fuscus

Ventilatory pattern and ventilatory responses to hypercapnia and hypoxia were investigated in torpid big brown bats at body temperatures of 5, 10, 20, 30 and 37 degrees C. The pattern of breathing at temperatures below 30 degrees C was intermittent, consisting of rhythmic breathing bouts separated by apneic periods with occasional sporadic, non-rhythmic breathing episodes. Overall ventilation (Ve) was matched consistently to overall oxygen consumption (MO2) over the entire range of temperatures with a mean air convection requirement (Ve/MO2) of 1.28 L/mmol. However, calculating the air convection requirement using only oxygen uptake acquired during ventilation yielded an ectotherm-like temperature relationship. Ventilation was stimulated at all temperatures by either increased inspired CO2 or decreased inspired O2. At 20 degrees C, graded hypercapnic stimulation increased the duration of the rhythmic bouts and decreased the duration of apneas until at high CO2 (greater than 3%) breathing was continuous. Hypoxic stimulation below about 7% O2 increased ventilation by selectively increasing the non-rhythmic ventilations and decreasing rhythmic bouts.

Acid-base state and intermittent breathing in the torpid bat, Eptesicus fuscus

The effects of intermittent breathing on acid-base state and blood gases were characterized in the torpid bat, Eptesicus fuscus, during steady-state torpor between body temperatures (Tb) of 5 and 37 degrees C. Arterial blood samples were taken from indwelling catheters without disturbing the torpid state. Arterial pH (pHa) of samples taken without knowledge of ventilatory state rose by 0.15 units from 37 to 5 degrees C with a delta pHa/delta Tb slope over this range of -0.0055 U/degrees C. However, at and below Tb = 20 degrees C, Eptesicus fuscus breathes intermittently with typical apneic periods of 40-150 min and 4-12 min at 10 and 20 degrees C, respectively. Samples taken at the end of a ventilatory bout and near the end of an apneic period at Tb = 20 degrees C revealed cyclic changes in pH (from 7.49 +/- 0.02 to 7.34 +/- 0.01), PO2 (from 96.6 +/- 3.4 to 30.8 +/- 3.9 Torr), and PCO2 (28.2 +/- 1.4 to 45.9 +/- 1.5 Torr). Between 10 and 37 degrees C, end-ventilatory pHa varied inversely with temperature with a delta pHa/delta T slope of -0.011 U/degrees C. Because intermittent breathing is common to many animals during hibernation, these results demonstrate the importance of coordinating blood sampling with ventilatory state for a reliable interpretation of acid-base regulation under these conditions.

Capillary-fiber geometry in pectoralis muscles of one of the smallest bats.

We previously reported striking similarities in the structural capacity for O2 flux in the highly aerobic flight muscles of a hummingbird and bat despite their significant differences in capillary-fiber geometry and number, and fiber size. However, the bats of that study (Eptesicus fuscus, BW 15-16 g) were about 5 times larger than the hummingbirds (Selasphorus rufus; BW 3-4 g). In this study, we examined the flight muscle in a bat of approximately the same size as the hummingbird to determine whether features found in the big brown bat would be accentuated or if there would be additional similarities with the hummingbird. The pectoralis muscle of pipistrelle bats Pipistrellus hesperus (BW 3-5 g) was perfusion-fixed in situ, processed for electron microscopy and analyzed by morphometry. Fiber size (group mean +/- SE, 314 +/- 22 microns 2 at 2.1 microns sarcomere length) and capillary geometry (high degree of tortuosity and branching) were remarkably similar to those in pectoralis muscle of the big brown bat. Thus distances from capillaries to the center of the fibers were not reduced in pipistrelle flight muscle (as in hummingbird) nor was capillary tortuosity and branching further increased (compared with big brown bat). Capillary-fiber surface ratio at a given mitochondrial volume/microns length of fiber was high and similar to that in big brown bat and hummingbird, consistent with the idea that the size of the capillary-fiber interface plays an important role in providing the great O2 flux potential in these muscles. In addition, capillary-fiber number at a given fiber mitochondrial volume per micron length of fiber was similar to that in other muscles including big brown bat and hummingbird flight muscle, bat hindlimb and rat M. soleus. This supports the notion of a close relationship between capillary number and mitochondrial volume on an individual fiber basis in aerobic muscles.