Larry L. Pater

Effects of helicopter noise on Mexican spotted owls

Military helicopter training over the Lincoln National Forest (LNF) in southcentral New Mexico has been severely limited to protect nesting Mexican spotted owls (Strix occidentalis lucida). To evaluate nesting and nonnesting spotted owl responses to helicopter noise, we measured flush frequency, flush distance, alert behavior, response duration, prey delivery rates, female trips from the nest, and nest attentiveness during manipulated and nonmanipulated periods, 1995-96. Chain saws were included in our manipulations to increase experimental options and to facilitate comparative results. We analyzed stimulus events by measuring noise levels as unweighted one-third-octave band levels, applying frequency weighting to the resultant spectra, and calculating the sound exposure level for total sound energy (SEL) and the 0.5-sec equivalent maximum energy level (LEQ max 0.5-sec) for helicopters, and the 10-sec equivalent average energy level (LEQ avg. 10-se) for chain saws. An owl-weighting (dBO) curve was estimated to emphasize the middle frequency range where strigiform owls have the highest hearing sensitivity. Manipulated and nonmanipulated nest sites did not differ in repro- ductive success (P = 0.59) or the number of young fledged (P = 0.12). As stimulus distance decreased, spotted owl flush frequency increased, regardless of stimulus type or season. We recorded no spotted owl flushes when noise stimuli were >105 m away. Spotted owls returned to predisturbance behavior within 10-15 min after a stimulus event. All adult flushes during the nesting season occurred after juveniles had left the nest. Spotted owl flush rates in response to helicopters did not differ between nonnesting (13.3%) and nesting seasons (13.6%; P = 0.34). Spotted owls did not flush when the SEL noise level for helicopters was <102 dBO (92 dBA) and the LEQ level for chain saws was -59 dBO (46 dBA). Chain saws were more disturbing to spotted owls than helicopter flights at comparable distances. Our data indicate a 105-m buffer zone for helicopter overflights on the LNF would minimize spotted owl flush response and any potential effects on nesting activity.

Recommendations for improved assessment of noise impacts on wildlife

Abstract Research to determine noise impacts on animals benefits from methodology that adequately describes the acoustical stimulus as well as the resulting biological responses. We present acoustical considerations and research techniques that we have found to be useful. These include acoustical definitions and noise measurement techniques that conform to standardized acoustical practice and advice for controlled experimentation to supplement behavioral observation. Specific considerations include characteristics of noise stimulus, selection of noise metrics, use of frequency-weighting algorithms tailored to a specific animal species, selection and placement of noise measurement equipment, and methods for documenting animal responses. We also present arguments for measuring the noise stimulus at the location and time of each response observation. Our purpose is to recommend some baseline terminology, metrics, and techniques prerequisite to effective assessment of noise impacts on terrestrial wildlife whenever and wherever potential conflicts arise.

Home Range, Spatial Overlap, and Burrow Use of the Desert Tortoise in the West Mojave Desert

Abstract Understanding the space use patterns of a population may provide crucial information regarding land management decisions, such as delineation of protected areas. Herein we provide a comprehensive analysis of factors affecting the space use of Desert Tortoises in the west Mojave Desert, including physical, social, and environmental variables. Our objectives were to determine how spatial overlap, as well as multiple parameters of burrow use, influence home range size of this species. Male tortoises were significantly larger than females and exhibited very different patterns of space and burrow use; however, body size did not affect these variables. Male home range (100% MCP) and core area (50% MCP) size averaged 65% and 73% larger than those of females. Burrow use by males and females affected core area size, but not home range area. Females exhibited a strong male bias in overlap of both estimates of space use and burrow sharing, while using a significantly lower number of burrows per year. However, males overlapped and shared burrows with a similar number of tortoises of either sex. In addition, a high degree of home range overlap between individuals suggests a lack of territoriality in this population, although this warrants further analysis. These results suggest that social factors may not be the primary determinants of space use in this Desert Tortoise population.

Response of Red-Cockaded Woodpeckers to Military Training Operations

ABSTRACT Military lands are a valuable resource in recovery of threatened, endangered, and at-risk species worldwide and have the highest density of threatened and endangered species of all major land management agencies in the United States. Many red-cockaded woodpeckers (Picoides borealis) that reside on federal lands occur on 15 military installations in the southeastern United States. This close association has increased concern over potential conflicts between conservation requirements of endangered species and the militarys mission of combat readiness. Our objectives were to 1) determine if military training operations affect behavior, reproductive success, and productivity of red-cockaded woodpeckers; 2) develop a frequency-weighting function to assess woodpecker hearing sensitivity; 3) identify factors that affect woodpecker responses to military training operations; 4) develop distance and dose-response thresholds for quantifying woodpecker responses to noise levels and stimulus distances; 5) characterize military training operations through quantification of sound levels, source identification, distance from active woodpecker nests, frequency spectra, duration, and frequency of occurrence; and 6) document baseline woodpecker nesting behavior. We conducted our study on the Fort Stewart Military Installation located in southeast Georgia, USA. Downy woodpeckers, as surrogates for red-cockaded woodpeckers, had their best hearing sensitivity within the peak range of the power spectrum of both downy and red-cockaded woodpecker vocalizations, which is at a higher frequency than that of a typical passerine. Overall, woodpeckers had a reduced auditory sensitivity relative to human hearing sensitivity and other species of small birds, especially in the frequency range >4 kHz. Woodpeckers were most sensitive in the 1.5- to 4.0-kHz range. Sensitivity appeared to drop off quickly at frequencies <1.0 kHz and >4.0 kHz. Overall, we did not find that the woodpecker-frequency-weighting function we developed provided a better predictor of woodpecker flush response compared with A-weighting. More research is needed to better understand the relationship between frequency-weighting functions and woodpecker response behavior. Potential breeding groups of woodpeckers across the population increased from 158 in 1997 to 181 in 2000, wheras nesting groups increased from 141 in 1998 to 170 in 2000, for overall increases of 14.6% and 20.6%, respectively, over the 3 years of this project. Fledging success rates for individual nests within the overall population remained consistent from 1998 to 2000, averaging 84.4%. Mean clutch sizes for woodpecker groups for 1998 to 2000 ranged from 2.75 to 3.01 eggs/nest, brood size ranged from 2.01 to 2.22 nestlings/nest, whereas the average number of young fledged ranged from 1.57 to 1.76 young/ occupied nest. We observed no difference in reproductive success or productivity between experimental and control-tested red-cockaded woodpecker groups. Overall, experimental test groups produced an average of 2.98 eggs/nest, 1.89 nestlings/nest, and 1.54 young/occupied nest from 1999 to 2000, compared with 2.73 eggs/nest, 1.91 nestlings/nest, and 1.57 young/occupied nest at control groups. We measured behavioral responses (nest attendance and arrivals and departures from the nest) of red-cockaded woodpeckers to military training events through direct and indirect (i.e., video surveillance) observation of 464.5 hours of woodpecker nesting behavior before and after controlled experimental events while recording and characterizing military-generated sound events using sound-recording equipment. We presented woodpeckers with actual 0.50-caliber blank machine gun fire and artillery simulators from controlled distances to develop distance and sound thresholds. We used video surveillance to document potential behavioral responses of woodpeckers primarily during nonexperimental military training operations in areas that could not be safely monitored and to determine baseline woodpecker nesting behaviors. We recorded 2,846 nonexperimental military noise events in 157 data sessions at 50 red-cockaded woodpecker groups from 1998 to 2000. We also recorded 206 experimental tests at 58 woodpecker groups during 1999 and 2000. Life-table analyses of flush response time showed that at short ranges (15–30 m) the flush response was stronger for artillery simulator blasts than for blank fire in both the incubation and the nestling phases. In contrast, at medium distances (45-60 m) blank fire tended to produce more flush responses than artillery fire in both incubation and nestling phases. At longer distances (>60 m), blank fire and artillery produced similar flush responses in the incubation phase, whereas flush response was stronger for blank fire than for artillery in the nestling phase. In general, most animals that responded to military activity flushed within 5 seconds of the stimulus event. Woodpeckers returned to nests within an average of 4.4 minutes after being flushed by artillery simulators and 6.3 minutes after 0.50-caliber blank-fire tests. Woodpecker flush response rates increased as stimulus distance decreased and sound levels increased, regardless of stimulus type or year. Woodpeckers did not flush from nests when 0.50-caliber blank machine gun fire and artillery simulators were >152 m away and sound-exposure levels (decibels [dB]) were <68 dBW (woodpecker-based frequency-weighting curve) and <65 dBW, respectively. We found that blast treatments reduced arrival rates of adults at the nest, with the amount of reduction dependent on the type of blast stimulus and number of helpers at the nest. On the other hand, blast treatments had no detectable effects on nest attendance. The effect of blank fire on incubation-phase arrivals over a 30-minute interval (about 40% reduction) was nearly twice that of artillery simulator fire (about a 20% reduction). There was no evidence supporting any effect of stimulus type on arrivals during the nestling phase. Blast stimuli during incubation reduced arrivals by 40% when no helpers were present, but the strength of this effect decreased to 28% when one helper was present, and was only 6% for nests with >2 helpers. Distance of the blast from the nest did not affect the response of arrival rates to blast treatments. Infrequent, short-duration military training exercises, as measured, did not appear to substantially impact red-cockaded woodpecker reproductive success and productivity on the Fort Stewart Military Installation. Our results may be applicable to other military installations where similar training activities and intensity levels occur. Additional research is needed to address possible habituation or sensitization of red-cockaded woodpeckers to human activities in proximity to active nest sites. Although we attempted to monitor woodpecker response to a number of military training activities, other types of military training operations or human-based activities with louder noise, longer duration, increased human presence, and greater frequency of occurrence could more negatively influence woodpecker nesting behavior and need to be investigated. Our results do not support the hypothesis that military maneuver training operations are limiting factors in the recovery of red-cockaded woodpeckers on military installations, based on our level and type of testing. Natural resource management policies on military installations have had a positive influence on the recovery of red-cockaded woodpeckers and probably outweigh the negative effects of typical military training.

Burrows of Desert Tortoises (Gopherus agassizii) as Thermal Refugia for Horned Larks (Eremophila alpestris) in the Mojave Desert

Abstract The Mojave Desert is one of the driest and hottest deserts in North America. One would expect that birds living in this desert would be specialists adapted to survive such an environment. However, most of the avifauna present in the Mojave Desert range into cooler, more-humid regions. We report observations of horned larks (Eremophila alpestris) using burrows of the desert tortoise (Gopherus agassizii) during summer as refugia from hot above-ground temperatures. We show that horned larks appear selective of the micro-environment they choose and that burrows are the coolest, most-humid, microsites available. By using burrows of desert tortoises, horned larks may reduce evaporative water loss by ≤65% and they may avoid physiological stress, or potentially death. Additional research should investigate the importance of burrows of desert tortoises to other species as it is likely to provide a key microhabitat to many species that reside in the Mojave Desert.

Logging truck noise near nesting northern goshawks

We measured noise levels of four logging trucks as the trucks passed within approximately 500 m of two active northern goshawk (Accipiter gentilis) nests on the Kaibab Plateau in northern Arizona in 1997. Neither a brooding adult female nor a lone juvenile exhibited any discernable behavioral response to logging truck noise, which peaked at 53.4 and 50.3 decibels (dBA). Spectral analysis showed most of the truck sound energy was in the vicinity of 80 Hz.

High-frequency measurements of blast wave propagation

Blast wave propagation measurements were conducted to investigate nonlinear propagation effects on blast waveform evolution with distance. Measurements were made with a wide-bandwidth capacitor microphone for comparison with conventional 3.175-mm (1/8-in.) microphones with and without baffles. It was found that the 3.175-mm microphone did not have sufficient high-frequency response to capture the actual rise times in some regions. For a source of 0.57 kg (1.25 lb) of C-4 plastic explosive, the trend observed is that nonlinear effects steepened the waveform, thereby decreasing the shock rise time, up to a range of 50 m. At 100 m, the rise times had increased slightly.

OSTEOPHAGY BY THE DESERT TORTOISE (GOPHERUS AGASSIZII)

Abstract The desert tortoise (Gopherus agassizii) has undergone significant declines in the past several decades. Thus, many carcasses are present across the desert landscape. Here we report on osteophagy by the desert tortoise, specifically the consumption of bones from deceased desert tortoises. Desert tortoises seem to have an appetite for calcium-rich substances. To our knowledge, this is the first documentation of desert tortoises consuming conspecific skeletal remains.

Minimizing sleep disturbance from blast noise producing training activities for residents living near a military installation

Field research was conducted during 2004 in the vicinity of a United States military installation to determine if awakening of residents due to blast noise from large military weapons might vary during the night. Analysis of the data indicates that awakening from blast noise is significantly less likely during the time period between midnight and 0200 h compared to time periods before midnight and approaching dawn. These findings suggest that postponing noisy evening training until after midnight could effectively reduce the negative impact of nighttime training on local residents and thus help to preserve nighttime training capabilities.

Assessment of training noise impacts on the Red‐cockaded woodpecker

Abstract : It is estimated that nearly a quarter of the remaining Red-cockaded Woodpecker (RCW) population resides on military installations in the southeastern United States. Such a close association has raised questions about the interaction between training and the conservation of Red-cockaded Woodpeckers on military land. Increased importance has been placed on determining how noise affects these species. This report presents second year results of a multiyear study to determine the effects of certain kinds of training noise on the endangered Red-cockaded Woodpecker. Preliminary data suggest that: measured levels of experimental noise from .50-caliber blank fire and artillery simulators did not affect RCW nesting success or productivity; Red-cockaded Woodpecker flush frequency increased as stimulus distance decreased, regardless of stimulus type; woodpeckers returned to their nests relatively quickly after being flushed; and noise levels in Red-cockaded Woodpecker nest cavities were substantially louder than levels recorded at the base of the nest tree.