Owl Conservation Research Articles

A Worldwide Review of Snowy Owl Feeding Ecology: The Importance of Lemmings and Voles in a Changing Climate

We compared Snowy Owl feeding ecology from 15 breeding season studies throughout Nearctic and Palearctic circumpolar regions. We used raw data and information theory to assess the owls’ feeding niche. Combined studies yielded 59,923 prey items, of which 59,585 were used for calculations. Overall, mean food niche breadth (FNB) was narrow: H′ = 1.95; R = 1.60, D = 0.526. In 10 of 15 studies, lemmings were > 71.8% of the owls’ diet. In four studies, Lemmus was > 90% of the diet, and in three studies Dicrostonyx was >90% of the diet. In three other studies, Lemmus represented 71.8%, 73.8%, and 84.0% of the diet. In one study, Lemmus and Dicrostonyx were about equal: 49.1% and 47.5%. In the four remaining studies, Microtus and Clethrionomys voles were important. In contrast, of 5888 winter prey items from seven North American studies, the mean FNB (H′ = 4.61) was twice that of 15 breeding season scores, FNB (H’ = 1.95). The Snowy Owl is primarily an obligate lemming predator for breeding. Changes to population ecology and distribution of lemmings due to climate change will have direct affects and effects on the Snowy Owls’ reproductive output. The conservation of Snowy Owls is the conservation of lemmings.

Detection dogs can help researchers with elusive forest owl conservation

AbstractElusive fauna are often studied indirectly, via traces they leave behind, or via other non‐invasive survey methods. Critically endangered Tasmanian masked owls are both rare and elusive, which hampers conservation efforts. Spotlighting and call playback often have low success rates in accurately determining the presence/absence of Tasmanian masked owls. Using indirect survey techniques for traces such as owl pellets can be more efficient and provide a more reliable source of detailed data regarding presence/absence, diet, health, population structure and environmental contaminants. However, pellets can be difficult for researchers to find in the field. We evaluate whether detection dogs are effective in finding owl pellets in two steps: an experimental trial comparing the performance of a dog team to that of an ecologist with significant field experience with masked owls; and in a pilot field study where the dog team searched potential owl habitat in Tasmanian forests. During the experimental trials, the dog team significantly outperformed the ecologist. The dog team was more sensitive, finding 89% versus 40% of pellets present for the ecologist, and took half as long to search an equivalent‐sized search area. The combined efficiency of the dog team was 4.5 times greater than that of an ecologist working alone. During the pilot study, in searching areas of potential masked owl habitat, no pellets were found. However, when sites were visited where owls were known to have been recently sighted, the dog team were able to find large numbers of owl pellets suitable for collection and potential data extraction. Our trials suggest that dogs can find owl pellets with considerably greater sensitivity and efficiency than ecologists working alone and that they would be best used in combination with targeted surveys, especially when the detection and subsequent collection of as many pellets as possible is desirable for DNA extraction or other analysis.

Frequent burning and limited stand-replacing fire supports Mexican spotted owl pair occupancy

Changing fire regimes have the potential to threaten wildlife populations and communities. Understanding species’ responses to novel fire regimes is critical to formulating effective management and conservation strategies in an era of rapid change. Here, we examined the empirical effects of recent and historical wildfire activity on Mexican spotted owl (Strix occidentalis lucida) populations in the southwestern United States. Using region-wide, standardized detection/non-detection data of Mexican spotted owl breeding pairs collected from 2015 to 2022, we found (i) higher rates of pair occupancy at sites that experienced more frequent fires in the three decades prior to the initiation of our study, and (ii) lower rates of local persistence at sites that experienced more extensive high-severity fire during the study. Historical fire regimes throughout much of our study area were characterized by high fire frequencies and limited high-severity components, indicating that Mexican spotted owls responded to wildfire in a manner consistent with their evolutionary environment. Management activities such as prescribed burning and mechanical thinning that aim to reduce stand-replacing fire risk and re-introduce the potential for frequent-fire regimes will likely benefit Mexican spotted owl conservation objectives, as well as promote more resilient forest landscapes.

Current and future effectiveness of protected areas for the conservation of endemic owls from the Atlantic Forest

Protected areas are essential conservation tools for mitigating the rapid decline of biodiversity. However, climate change represents one of the main challenges to their long‐term effectiveness, as it induces rapid changes in the geographical distribution of many species. We used ecological niche modelling to predict the impacts of climate change on the distribution of five endemic owls in the Atlantic Forest and evaluated the effectiveness of the protected areas network for their conservation. The results indicate that the protected areas network is currently effective in terms of representativeness for most species; however, there will be a decline for all species in the coming decades because of climate change. We found that the ecoregions in the northern part of the Atlantic Forest will experience a higher loss of species, whereas those ecoregions in the southern part will be important stable climatic refuges in the future. Therefore, we emphasize the need to complement the network of protected areas to increase their representativeness in the distribution of species that will be affected by climate change, reducing species loss and increasing connectivity between suitable areas. We hope the results presented herein will serve as a basis for decision‐makers to re‐evaluate and improve current conservation policies and decisions in order to address the challenges posed by climate change and secure the survival of these species.

Repurposing transfer learning strategy of computer vision for owl sound classification

Accurately predicting an owl species based on its sound can be helpful for owl conservation. To build an accurate model for owl sound classification, deep learning is currently the most preferred algorithm, due to its excellent performance for modeling audio data. However, deep learning is generally underperformed for a small dataset, which is the case for recognizing scops owl sound. To overcome the issue, we proposed a transfer learning strategy, which is common for computer vision tasks, that can alleviate overfitting in a deep learning model for the owl sound classification. In our approach, we propose a neural network architecture consisting of the backbone of a EfficientNet model pre-trained on the massive ImageNet database. The model takes the sound input that has been converted as two image representations: Spectrogram and Mel Frequency Cepstral Coefficients. Our strategy enables the use of a relatively small size of pre-trained image classification model, which is widely available, for transfer learning in owl sound classification. Deploying the lightweight model in an automatic sound classifier provides a fast and accurate tool for various owl conservation purposes.

Fire severity and pre-fire forest composition affect Northern Hawk Owl presence in burned forests in western North America

Wildfire is an important natural disturbance shaping the boreal forests of North America. Not surprisingly, many species have adapted to benefit from the structural or functional changes in response to fire. Of these post-fire species, the Northern Hawk Owl (Surnia ulula caparoch) is one of the least studied species on the continent. We surveyed 18 recent fires in the boreal forest region of Alberta, Canada, ranging in age from 1 to 14 years post-fire, to improve our understanding of post-fire habitat relationships for this species. Hawk owls were present in fires ranging from 2 to 11 years post-fire, and occupied burns ranging in size from 1,000–272,000 ha. Hawk owls were strongly associated with areas of older deciduous-dominated forest, based on pre-fire forest inventory. Hawk owl responses to pre-fire forest age structure and composition were consistently stronger at the 1000 m radius (home range) extent than the 400 m (nest site) extent. We also found hawk owls responded differently to time since fire, with an immediate (e.g. 2–6 yr) response to low severity fire and a delayed (10–11 yr) response to high severity fire. We recommend future surveys for this species be conducted earlier in the day, ideally within a few hours of sunrise, based on the timing of detection in this study. Finally, the retention of large patches (e.g. > 300 ha) of older, deciduous-dominated habitat within post-fire forests may be an important management consideration for the conservation of hawk owls and other post-fire species.

Using thresholds to determine priorities for apex predator conservation in an urban landscape

As landscapes are increasingly modified due to anthropogenic processes such as urbanisation or development for agriculture, the need to understand wildlife habitat requirements is imperative. This is particularly pertinent for species that are threatened, or apex predators with specific nest, den, or food requirements. Identifying responses to habitat with thresholds can provide an understanding of what resources species are using or avoiding, and their interactions with the surrounding environment. In this research we investigated space use and habitat requirements of the threatened apex predator, the powerful owl (Ninox strenua) in Greater Melbourne, Australia. We deployed GPS devices to 21 urban powerful owls over five years and found owls had an average home range size of 397 ha, and an average core-range of 84 ha. Home range size and positioning was driven by tree cover and urban land cover, while core ranges were restricted to treed environments with a limited area of impervious surfaces and housing. We used thresholds to identify-three priorities for powerful owl conservation in Melbourne. Priority 1: Ensuring river corridors and public open spaces are adequately protected. Priority 2: Limit property densities near rivers and protected areas. Priority 3: Finding opportunities for revegetation to expand and enhance habitat over time. Our research demonstrates how species-specific thresholds can inform land use planning to ensure wildlife species are maintained within highly modified environments.

Migratory Pathways, Stopover Locations and Wintering Grounds of Southern Spanish Eurasian Scops Owls Otus scops

Little is known about the migration and wintering distribution of Eurasian Scops Owls Otus scops. We deployed GPS-loggers on breeding Scops Owls from a southern Spanish population to analyse migratory routes and migration timing of this trans-Saharan migrant. Tag deployment had no short- or long-term effects on Scops Owls. Individuals followed rapid autumn and spring migrations along the coasts of Morocco and Western Sahara and the western edge of the Sahara desert. South Spanish breeding Scops Owls wintered across a large area of West Africa; within Mauritania, Senegal, Mali, Gambia, Guinea and Sierra Leone, where they stayed apart from one another for 4-5 months. Wintering sites were primarily in tree-covered habitats suggesting that these are important for Scops Owl conservation year-round.—Avilés, J.M., Rodríguez-Ruiz, J., Cruz-Miralles, Á., Abad-Gómez, J.M. & Parejo, D. (2022). Migratory pathways, stopover locations and wintering grounds of southern Spanish Eurasian Scops Owls Otus scops. Ardeola, 69: 129-139.

Conspecific and congeneric interactions shape increasing rates of breeding dispersal of northern spotted owls.

Breeding dispersal, the movement from one breeding territory to another, is rare for philopatric species that evolved within relatively stable environments, such as the old‐growth coniferous forests of the Pacific Northwest. Although dispersal is not inherently maladaptive, the consequences of increased dispersal on population dynamics in populations whose historical dispersal rates are low could be significant, particularly for a declining species. We examined rates and possible causes of breeding dispersal based on a sample of 4,118 northern spotted owls (Strix occidentalis caurina) monitored in seven study areas over 28 yr, 1990–2017, in Oregon and Washington, USA. Using a multistate mark–resight analysis, we investigated the potential impacts of an emergent congeneric competitor (barred owl Strix varia) and forest alteration (extrinsic factors), and social and individual conditions (intrinsic factors) on 408 successive and 1,372 nonsuccessive dispersal events between years. The annual probability of breeding dispersal increased for individual owls that had also dispersed in the previous year and decreased for owls on territories with historically high levels of reproduction. Intrinsic factors including pair status, prior reproductive success, and experience at a site, were also associated with breeding dispersal movements. The percent of monitored owls dispersing each year increased from ˜7% early in the study to ˜25% at the end of the study, which coincided with a rapid increase in numbers of invasive and competitively dominant barred owls. We suggest that the results presented here can inform spotted owl conservation efforts as we identify factors contributing to changing rates of demographic parameters including site fidelity and breeding dispersal. Our study further shows that increasing rates of breeding dispersal associated with population declines contribute to population instability and vulnerability of northern spotted owls to extinction, and the prognosis is unlikely to change unless active management interventions are undertaken.

Rapid colonisation, breeding and successful recruitment of eastern barn owls (

Abstract Context The introduced house mouse (Mus domesticus) causes significant economic damage to Australia’s agricultural enterprises. As part of the Marna Banggara Rewilding Project on the southern Yorke Peninsula (SYP), the present study focused on the eastern barn owl (Tyto alba delicatula) as a potential bio-controller of mice, by providing nesting spaces where natural hollows are limited. Aims To design an appropriate pole-mounted wooden nest box, and to enhance barn-owl-breeding and house-mouse-hunting capacity on farmland adjacent to remnant native vegetation. Methods A prototype nest box was collaboratively designed with a nest box manufacturer using data from previous barn owl studies and anecdotal reports. Eleven pole-mounted wooden boxes with platforms were installed at distances >1.4 km apart on properties near Warooka, southern Yorke Peninsula (SYP), and monitored over a 6-month period using external trail cameras. Key results Of the 11 nest boxes installed, 55 percent were colonised within a month after establishment, and 82 percent were colonised within 7 months. Occupied nest boxes were actively used by paired owls for mating, breeding and rearing of chicks, which resulted in up to 35 fledgling owlets. Conclusions The nest box design successfully supported eastern barn owl colonisation and reproduction on the SYP. The inclusion of the platform not only provided easy, minimally invasive monitoring of barn owl activity and prey intake by researchers, but also increased usable space for barn owl behaviours, such as copulation and wing flapping. Implications The important nest box design elements featured in this paper, such as the platform, high entrance hole, predator-proof pole and rear door access, can be implemented in barn owl conservation, research and on farms where alternative nesting sites are limited.

“Uncanny Creatures of the Dark.”

Belief systems of human societies are deeply related with animals, which are symbolised in traditional narratives. Here we review reported cases from around the world and our own ethnographic observations from southern Chile, to analyse beliefs associated with owls. In particular, we explore the role that owls play in traditional narratives and the likely reasons of their saliency, including their connections with the extraordinary. For the latter, we utilise the concept of “the uncanny” to analyse how owls generate a feeling of something not simply mysterious but, more specifically, something strangely familiar. Owls trigger unsettling experiences of the “normal,” with the ensuing feelings of unhomeliness, which may explain their saliency across human societies. Finally, we discuss that the uncanny nature of owls is precisely what locates them in a culturally stimulating position and what should be considered by conservationists and politicians to tackle a more integrative approach to owl conservation.

Invited Commentary: When a Conservation Conflict Comes Full Circle—The Spotted Owl Conflict is a Wicked Problem

The conservation of the Spotted Owl (Strix occidentalis) has been the center of a 40-yr conflict between those who wish to conserve owls and old growth forests and those who wish to log trees as commodities. Although the Spotted Owl conflict seems unique because it has lasted so long, it is no different than many other conservation conflicts in which many scientists—and raptor biologists specifically—might find themselves engaged. Therefore, I explore the commonality among conflicts, including specific details of the Spotted Owl case, to illustrate the problems inherent in conservation conflicts and why these disputes last so long. I suggest two general motivations that I believe capture the reasons behind people's willingness to engage in conflict: money and passion. Yet the specific motivations (e.g., economic well-being and ideology) nested within these general motivations are complex and interconnected. This complexity can lead to intractable situations, such as Spotted Owl conservation, which have been defined as “wicked problems” that cannot be resolved to the satisfaction of most. But understanding these broad motivations and identifying the wide variety of specific motivations nested within them may yield opportunities to manage—rather than resolve—a conservation conflict. Accordingly, I present a conceptual overview of the owl situation as a case study, along with some guidelines for raptor biologists working in conflict environments.

Haemoproteus syrnii (Haemosporida: Haemoproteidae) in owls from Brazil: morphological and molecular characterization, potential cryptic species, and exo-erythrocytic stages.

Haemoproteus syrnii is a haemosporidian parasite found in owls. Although morphological and molecular data on the species is available, its exo-erythrocytic development was never researched. In this study, we provide the morphological, morphometric, and molecular characterization of H. syrnii populations found in owl species from Minas Gerais, southeast Brazil. We also characterized the coalescent species delimitation based on the molecular and histopathology data. Samples from 54 owls from six different species were analyzed, generating 11 sequences of the cyt b gene, from which six were new sequences. The overall prevalence of infection was high (72.22%). The H. syrnii sequences were grouped into two well-supported independent clades, which included other Haemoproteus (Parahaemoproteus) species. This was supported by both the coalescent species delimitation analysis and by the genetic divergence between lineages of these distinct clades. There were small morphological and morphometric differences within the population presented in this study. However, when compared with other studies, the molecular analysis demonstrated considerable intraspecific variation and suggests potential cryptic species. The histopathological analysis revealed, for the first time, that lungs and skeletal muscle are exo-erythrocytic stage location of H. syrnii, and that the parasite is linked to the histopathological changes found in owls. This study brings new data from Haemoproteus species biology and host infection, and improves host-parasite relationship understanding under an owl conservation perspective.

Biomonitoring of Owls and Their Environment Using Pellets and Feathers.

Owls are predators that perform important ecological functions. There are several threats to owl conservation such as the bioaccumulation of chemicals through environmental contamination. The high probability of bioaccumulation in these animals is related to their role as predators and high trophic positions. The objective of this study was to quantify four elements (cadmium, chromium, nickel, and lead) as the biomarkers of environmental exposure in owls. To this end, we analyzed pellets and feathers of different owl species. These matrices were contaminated with all four elements, with chromium most commonly detected. Chromium and nickel were found in the pellets in all 10 months of the study, and May was the month with the highest concentrations of all the elements. Tyto furcata appears to bioaccumulate more elements in its feathers than Megascops spp. and Athene cunicularia. Our findings showed bioaccumulation of these four elements in owls and their environment.

California spotted owl habitat selection in a fire-managed landscape suggests conservation benefit of restoring historical fire regimes

Wildland fire is a disturbance that shapes frequent-fire forest ecosystems and the life-histories of wildlife species that inhabit them. The California spotted owl (Strix occidentalis occidentalis) is an iconic old-forest species that evolved under a frequent-fire regime in western North America. While recent studies have focused on owl response to large, severe fire events, relatively little is known about how owls might respond to prescribed fires and wildfires managed for resource benefit. Therefore, understanding how owls use landscapes that are managed using fire may offer insight into how owls respond to fire management. We studied the breeding season nocturnal foraging habitat selection of 22 GPS-tagged California spotted owls in three national parks (Yosemite, Sequoia, and Kings Canyon) in the Sierra Nevada, California, USA where natural fires have largely been allowed to burn during the past 50 years and controlled burning has been used to target additional areas. Consistent with other studies of this species, owls selected forests dominated by medium and large trees and avoided areas with smaller trees within their home ranges based on step selection analysis. Owls neither selected nor avoided forests burned by low- and moderate-severity, or high-severity fires, yet avoided larger patches of severely-burned forest (odds of selection decreased by 20% for every 10 ha increase in severely-burned patch area). These results indicated the importance of patch characteristics, suggesting that larger patches reflected either lower quality foraging habitat or increased predation risk, even in these frequent-fire landscapes where “large” severely-burned patches were small compared to those common after megafires. Additionally, selection strength increased for areas burned recently by lower-severity fire and, to a lesser extent, by older fires (largely of lower severity) as the extent of these burned areas increased within individual home ranges. These results suggested that lower-severity fire benefitted spotted owls and that these benefits declined over time. Thus, our findings are consistent with the hypothesis that California spotted owls are adapted to historical frequent-fire regimes of overall lower-severity with small high-severity patches. We hypothesize that fire management, coupled with medium- and large-tree retention, likely maintains high quality spotted owl habitat and may contribute to the observed owl population stability in Sequoia and Kings Canyon National Parks, compared to declining populations on three national forests. Finally, our results indicated that fire management, as practiced in these national parks, could benefit owl conservation elsewhere if challenges to the reintroduction of frequent-fire regimes can be overcome.

Invited Commentary: When a Conservation Conflict Comes Full Circle—The Spotted Owl Conflict is a Wicked Problem: A Plenary Address Presented at the Raptor Research Foundation 53rd Annual Conference, Fort Collins, Colorado, 7 November 2019

The conservation of the Spotted Owl (Strix occidentalis) has been the center of a 40-yr conflict between those who wish to conserve owls and old growth forests and those who wish to log trees as commodities. Although the Spotted Owl conflict seems unique because it has lasted so long, it is no different than many other conservation conflicts in which many scientists—and raptor biologists specifically—might find themselves engaged. Therefore, I explore the commonality among conflicts, including specific details of the Spotted Owl case, to illustrate the problems inherent in conservation conflicts and why these disputes last so long. I suggest two general motivations that I believe capture the reasons behind people's willingness to engage in conflict: money and passion. Yet the specific motivations (e.g., economic well-being and ideology) nested within these general motivations are complex and interconnected. This complexity can lead to intractable situations, such as Spotted Owl conservation, which have been defined as “wicked problems” that cannot be resolved to the satisfaction of most. But understanding these broad motivations and identifying the wide variety of specific motivations nested within them may yield opportunities to manage—rather than resolve—a conservation conflict. Accordingly, I present a conceptual overview of the owl situation as a case study, along with some guidelines for raptor biologists working in conflict environments.

Barred Owl Effects on Spotted Owl Resource Selection: A Meta‐Analysis

ABSTRACTWe quantified the effects of barred owls (Strix varia) on fine‐scale (~2 ha), spatially explicit selection of putative foraging habitat by 175 radio‐tagged northern spotted owls (Strix occidentalis caurina) from 1998 to 2012 in western Oregon and northern California, USA. We constructed annual nighttime discrete‐choice resource selection functions (RSFs) for northern spotted owls in 8 study areas. We compared RSFs from pooled data from 4 study areas where barred owls were absent or rare (≤14% of spotted owl territories potentially influenced by barred owls) with RSFs from 4 study areas where barred owls were abundant (≥89% of spotted owl territories potentially influenced by barred owls), and we conducted a meta‐analysis of all 8 study areas. Top‐ranked RSFs for individual study areas indicated that the relative probability a forest patch was selected by northern spotted owls for foraging was most strongly associated with basal area of large coniferous trees (≥66 cm diameter at breast height [dbh]) or quadratic mean diameter (QMD, the diameter of trees of average basal area) of all coniferous trees. The influence of such trees was non‐linear, usually quadratic, in 7 study areas, suggesting that an optimal basal area of large‐diameter trees or QMD may be associated with selection of foraging patches. The relative probability of selection of such trees decreased nonlinearly with increasing distance from nest sites in ≥4 study areas. Basal area of all or specific hardwood tree species was linearly associated with increases in the relative probability of a patch being used for foraging in 7 of 8 study areas. The relative probability of selection was also positively associated with densities of large snags (>50 cm dbh), coarse woody debris, and undergrowth shrubs in most study areas where we estimated those covariates. The relative probability that a patch was selected decreased nonlinearly with increasing distance from streams (7 study areas), increasing elevation (5 study areas), and decreasing slope (5 study areas). Barred owls exerted strong effects on habitat selection by spotted owls, which may have attempted to minimize interference competition via spatial segregation. Spotted owls occupying study areas where barred owls were abundant used foraging patches at greater distances from streams, at greater distances from nest sites, and on steeper and warmer slopes than those occupying areas with few or no barred owls. In addition, northern spotted owls in areas where barred owls were abundant exhibited reduced selection for large‐diameter trees close to nest sites but may have compensated by increasing use of large trees in home‐range locations distant from nest sites. Programs that seek to improve the link between spotted owl demographic performance or occupancy rate and habitat conditions should account for the influences of fine‐scale variation in vegetation composition and structure and physiographic conditions. Forest managers may contribute to spotted owl conservation via silvicultural prescriptions that retain coarse woody debris and large snags, promote undergrowth shrubs, and retain intermediate to high densities of large, old shade‐intolerant early‐seral trees and riparian hardwoods within and beyond core areas surrounding nest sites. © 2019 The Wildlife Society.

Site occupancy and reproductive dynamics of California spotted owls in a mixed-ownership landscape

Biodiversity conservation in mixed-ownership landscapes often depends on contributions from privately-owned lands, where natural resource development can alter and produce novel habitat conditions for species of conservation concern. A lack of research on private lands stemming from access issues and concerns over regulatory outcomes, however, often limits evaluation of the impact of land management. The California spotted owl (Strix occidentalis occidentalis), for example, often occurs in mixed-ownership landscapes but research on this species has occurred primarily on public lands. Therefore, we conducted the first large-scale private-public cooperative and comparative analyses of California spotted owls inhabiting mixed-ownership landscapes in the Sierra Nevada, California, USA. We surveyed 151 spotted owl sites from 2013 to 2017 within two study systems: one comprised primarily of public lands (national forests) where the owl population has declined over the last ∼20 years and a set of study areas comprised mostly of private lands on which relatively high estimates of site occupancy were recently reported. Multistate occupancy modeling indicated that the probability of occupancy and successful reproduction by owls depended on site status in the previous year, with both probabilities highest at sites where owls successfully reproduced in the previous year, intermediate at occupied sites where owls had not successfully reproduced, and lowest at previously unoccupied sites. Site occupancy probability was higher at low-elevation sites and lower at sites that contained more open area and younger forest. Successful reproduction by owls was also more likely at low-elevation sites and at sites with more north-facing slope and younger forest with high basal area of hardwoods. Study areas with more private lands tended to occur at lower elevations and have greater amounts of younger forest with high basal area of hardwoods, which may have contributed to higher occupancy and reproductive probabilities than the study area with more public land. Thus, differences in occupancy and reproductive probabilities between study areas appeared to be the result of differences in topographic and vegetation conditions that likely promote populations of key spotted owl prey species. Our results suggest that private lands in mixed-ownership landscapes may contribute to spotted owl conservation by conferring different benefits to owls than public lands and, more broadly, highlight the importance of including private lands in conservation research and planning.

Space use, forays, and habitat selection by California Spotted Owls (Strix occidentalis occidentalis) during the breeding season: New insights from high resolution GPS tracking

Our current understanding of the relationship between imperiled species and forest management can benefit from global positioning system (GPS) technologies. Fauna of lateseral stage forests have historically been difficult to detect and track in rugged terrain, leading to challenges in movement characterization and conservation. We investigated movement of California Spotted Owls (Strix occidentalis occidentalis) using automated GPS loggers affixed to 15 owls in the northern Sierra Nevada, California. We used >17,000 locations from individual owls to characterize homerange size, movement distances, and roosting and foraging habitat selection at four spatio-temporal scales (landscape, home range, foray, nightly) during the breeding season (April–August). Additionally, we assessed owl use of Protected Activity Centers (PACs), which are designated by the U.S.D.A. Forest Service to protect nesting and roosting habitat. Our results corroborated some previous findings about habitat requirements of California Spotted Owls, while also revealing new nuances in space use and habitat selection. Roosting and foraging owls selected stands with high canopy cover and large trees at multiple spatio-temporal scales, with foraging owls showing strongest selection at the largest (landscape) scale investigated. Although owls selected for PACs while foraging and roosting, PACs protected less than one quarter of foraging space use (volume of use) and fewer than half of observed roosts during the breeding season. Female owl home ranges were double the size of male home ranges, and distances travelled from the nest by females were 1.3 times greater than distances travelled by males, with non-breeding females travelling farthest and visiting up to six PACs during a single breeding season. Foraying behavior of this sort has not been documented previously in California Spotted Owls. Our findings support protection of later seral stage forest attributes for roosting and foraging California Spotted Owls. Given their selection for later seral forest attributes, strongest evidence of foraging habitat selection at the landscape scale, long distances travelled by owls and limited habitat protection afforded by PACs, habitat connectivity across the landscape is likely an important component for owl conservation, and distribution of current protected areas may be inadequate for this wide-ranging species.

Detecting Burrowing Owl Bloodmeals in Pulex irritans (Siphonaptera: Pulicidae).

Pulex irritans L. is a cosmopolitan flea species that infests a wide variety of hosts. In North America it generally parasitizes large wild mammals, but in the Pacific Northwest an association has emerged between P. irritans and the western burrowing owl (Athene cunicularia hypugaea). While investigators have recognized this association for decades, it has not been clear if P. irritans feeds on burrowing owls, or if the owls serve exclusively as phoretic hosts. Here we describe using a real-time assay that was originally developed to identify bloodmeals in Ugandan cat fleas (Ctenocephalides felis Bouché) to detect burrowing owl DNA in P. irritans collected from burrowing owls in southern Idaho. Of 50 fleas tested, 12 had no detectable vertebrate bloodmeal. The remaining 38 (76%) contained burrowing owl DNA. The assay did not detect vertebrate DNA in unfed fleas exposed to owl or mouse pelts and is therefore unlikely to detect DNA in fleas from vertebrates that have served exclusively as phoretic hosts. We conclude that P. irritans feeds on burrowing owls. We discuss the potential implications of this finding for burrowing owl conservation and enzootic plague dynamics.