David K. Delaney

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.

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.

Activity patterns of nesting Mexican Spotted Owls

We collected 2,665 hr of behavioral information using video surveillance on 19 Mexican Spotted Owl (Strix occidentalis lucida) pairs between 25 April and 26 July 1996. Prey deliveries per day increased as the nesting season progressed, with an average of 2.68 prey deliveries during incubation, 4.10 items during brooding, and 4.51 items during the nestling phase. The highest delivery rates were concentrated between l-3 hours before sunrise (02:00-05:00) and l-3 hours after sunset (18:00-21:00). Trip duration during diurnal hours increased 14 fold from incubation through the nestling phase, compared with a 7.2 fold increase during nocturnal hours. Nest bout duration decreased during both diurnal (36%) and nocturnal hours (76%) across the nesting season. Nest attentiveness decreased as the nesting season progressed, from 97% during the incubation phase to 47% during the nestling phase. Owls attended nests at higher rates during diurnal hours than nocturnal hours across all nesting phases. Activity patterns of Mexican Spotted Owls showed marked cyclical changes in response to ecological factors. Fluctuations in nesting behavior were related to changes in nesting phase and time of day.

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.

Use of Automated Radio Telemetry to Detect Nesting Activity in Ornate Box Turtles, Terrapene Ornata

Abstract Researchers often employ radio telemetry to locate study animals efficiently, but the time required to locate individuals can make monitoring large populations difficult and costly. In 2010–2011 we located nesting ornate box turtles (Terrapene ornata) in a large group of radio-tagged animals. To minimize search efforts, we investigated whether automated radio telemetry and the signal change method could be used to identify nesting activity before locating animals. The signal change method relies on the principle that any movement of a radio transmitter, including minor changes in orientation, can strongly affect the intensity of the transmitters signal at a stationary receiving station. Using video recordings of free-ranging radio-tagged turtles, we confirmed that transmitter signal strength values can be analyzed to identify periods of box turtle activity. Early in the 2010 nesting season, automated telemetry observations indicated that some females engaged in nocturnal activity. Previous reports indicate that ornate box turtles often nest at night but are otherwise inactive after dark. Based upon this information and relatively little indication of nocturnal activity by males, we hypothesized that nocturnal activity corresponded to nesting. We subsequently monitored female nighttime activity in near real time, hand-tracked four night-active individuals, and found three of these turtles nesting. In 2011 we again selectively hand-tracked night-active females and located nests for 12 of 18 study animals, which approximates the expected annual reproductive rate for our population. We demonstrate that the signal change method can be used to identify nesting activity in ornate box turtles and suggest this method may be of use in other species that nest outside of their normal activity periods.

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.

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.

Activity Patterns of Ornate Box Turtles (Terrapene ornata) in Northwestern Illinois

Activity patterns of ectothermic animals are affected by weather, time of day, and season, but quantifying these effects can be logistically challenging. We used an automated radio telemetry system to quantify Ornate Box Turtle (Terrapene ornata) activity patterns for two years in northern Illinois. Continuously collected activity data were paired with meteorological data collected from the site to determine factors influencing turtle behavior. Temperature, relative humidity, rain, year, month, time of day, and reproductive status affected activity levels. Increased activity levels corresponded with rain events, and males were generally more active than females, especially during spring and late summer. Overall, turtles were less active during an uncharacteristically warm and dry year compared to a year with conditions that were closer to the long-term average. Bimodal daily activity patterns have been reported in more southerly populations, and we found similar patterns near the species’ northern range limit, indicating that thermal constraints may limit activity of this species across its range. Activity comparisons between a year with normal meteorological conditions and an abnormally warm and dry year provide insight to the effect that further onset of climate change may have on the activity of Ornate Box Turtles.

Kleptoparasitism of a Red-Cockaded Woodpecker (Picoides borealis) Nest Cavity by a Red-Bellied Woodpecker (Melanerpes carolinus)

Abstract We report the kleptoparasitism of a Picoides borealis (Red-cockaded Woodpecker) cavity by a Melanerpes carolinus (Red-bellied Woodpecker). We believe this is the first video documenting kleptoparasitism of a Red-cockaded Woodpecker nest by a male Red-bellied Woodpecker in which both a nestling and an attending adult Red-cockaded Woodpecker adult were forcibly ejected. The Red-bellied Woodpecker was resolute in its attempt to usurp the nest, reaching into the cavity over 2000 times in an attempt to evict the cavity occupants. The male Red-bellied Woodpecker and his mate took over the cavity soon after. Adult Red-cockaded Woodpeckers continued to visit their nest cavity during diurnal hours for 2 days post-kleptoparasitism. It is important that resource managers incorporate proactive management techniques to lessen the impact of interspecific competition for cavities, especially in smaller or fragmented Red-cockaded Woodpecker populations.