Older forests function as energetic and demographic refugia for a climate-sensitive species.

More frequent and extreme heat waves threaten climate-sensitive species. Structurally complex, older forests can buffer these effects by creating cool microclimates, although the mechanisms by which forest refugia mitigate physiological responses to heat exposure and subsequent population-level consequences remain relatively unexplored. We leveraged fine-scale movement data, doubly labeled water, and two decades of demographic data for the California spotted owl (Strix occidentalis occidentalis) to (1) assess the role of older forest characteristics as potential energetic buffers for individuals and (2) examine the subsequent value of older forests as refugia for a core population in the Sierra Nevada and a periphery population in the San Bernardino Mountains. Individuals spent less energy moving during warmer sampling periods and the presence of tall canopies facilitated energetic conservation during daytime roosting activities. In the core population, where tall-canopied forest was prevalent, temperature anomalies did not affect territory occupancy dynamics as warmer sites were both less likely to go extinct and less likely to become colonized, suggesting a trade-off between foraging opportunities and temperature exposure. In the peripheral population, sites were more likely to become unoccupied following warm summers, presumably because of less prevalent older forest conditions. While individuals avoided elevated energetic expenditure associated with temperature exposure, behavioral strategies to conserve energy may have diverted time and energy from reproduction or territory defense. Conserving older forests, which are threatened due to fire and drought, may benefit individuals from energetic consequences of exposure to stressful thermal conditions.

Using the ecological significance of animal vocalizations to improve inference in acoustic monitoring programs.

Recent bioacoustic advances have facilitated large-scale population monitoring for acoustically active species. Animal sounds, however, can of information that is underutilized in typical approaches to passive acoustic monitoring (PAM) that treat sounds simply as detections. We developed 3 methods of extracting additional ecological detail from acoustic data that are applicable to a broad range of acoustically active species. We conducted landscape-scale passive acoustic surveys of a declining owl species and an invasive congeneric competitor in California. We then used sex-specific vocalization frequency to inform multistate occupancy models; call rates at occupied sites to characterize interactions with interspecific competitors and assess habitat quality; and a flexible multivariate approach to differentiate individuals based on vocal characteristics. The multistate occupancy models yielded novel estimates of breeding status occupancy rates that were more robust to false detections and captured known habitat associations more consistently than single-state occupancy models agnostic to sex. Call rate was related to the presence of a competitor but not habitat quality and thus could constitute a useful behavioral metric for interactions that are challenging to detect in an occupancy framework. Quantifying multivariate distance between groups of vocalizations provided a novel quantitative means of discriminating individuals with ≥20 vocalizations and a flexible tool for balancing type I and II errors. Therefore, it appears possible to estimate site turnover and demographic rates, rather than just occupancy metrics, in PAM programs. Our methods can be applied individually or in concert and are likely generalizable to many acoustically active species. As such, they are opportunities to improve inferences from PAM data and thus benefit conservation.

Uso de la Importancia Ecológica de las Vocalizaciones Animales para Mejorar la Inferencia en los Programas de Monitoreo Acústico Resumen Los avances bioacústicos recientes han facilitado el monitoreo a gran escala de poblaciones de especies acústicamente activas. Sin embargo, los sonidos de animales pueden transmitir cantidades sustanciales de información que queda utilizada insuficientemente en las estrategias comunes de monitoreo acústico pasivo (MAP) que tratan a los sonidos como simples detecciones. Desarrollamos tres métodos de extracción de detalles ecológicos adicionales de los datos acústicos que son aplicables a una gama amplia de especies acústicamente activas. Realizamos censos acústicos pasivos a escala de paisaje para una especie de búho en declinación y para un competidor congenérico invasivo en California. Después utilizamos la frecuencia de vocalizaciones específicas por sexo para orientar los modelos multiestado de ocupación; las tasas de llamados en sitios ocupados para caracterizar las interacciones con los competidores interespecíficos y evaluar la calidad de su hábitat; y una estrategia multivariada flexible para diferenciar a los individuos con base en sus características vocales. Los modelos multiestado de ocupación brindaron estimaciones novedosas para las tasas de ocupación por estado reproductivo que fueron más sólidas ante las detecciones falsas y capturaron el número de asociaciones de hábitat más sistemáticamente que los modelos de estado único agnósticos al sexo. La tasa de llamados estuvo relacionada con la presencia de un competidor pero no con la calidad del hábitat y por lo tanto podría constituir una medida conductual útil para las interacciones que son difíciles de detectar en un marco de trabajo de ocupación. La cuantificación de la distancia multivariada entre los grupos de vocalizaciones proporcionó un medio cuantitativo novedoso para discriminar a los individuos con ≥20 vocalizaciones y una herramienta flexible para balancear los errores del tipo I y del tipo II. Por lo tanto, parecer que hay posibilidad de estimar las tasas demográficas y de rotación, en lugar de sólo las medidas de ocupación, en los programas MAP. Nuestros métodos pueden aplicarse individualmente o de manera conjunta y es probable poder generalizarlas para muchas especies acústicamente activas. Dicho así, son oportunidades para mejorar las inferencias de los datos MAP y por lo tanto, beneficiar a la conservación.

Effects of forest management on California Spotted Owls: implications for reducing wildfire risk in fire­prone forests.

Management of many North American forests is challenged by the need to balance the potentially competing objectives of reducing risks posed by high-severity wildfires and protecting threatened species. In the Sierra Nevada, California, concern about high-severity fires has increased in recent decades but uncertainty exists over the effects of fuel-reduction treatments on species associated with older forests, such as the California Spotted Owl (Strix occidentalis occidentalis). Here, we assessed the effects of forest conditions, fuel reductions, and wildfire on a declining population of Spotted Owls in the central Sierra Nevada using 20 years of demographic data collected at 74 Spotted Owl territories. Adult survival and territory colonization probabilities were relatively high, while territory extinction probability was relatively low, especially in territories that had relatively large amounts of high canopy cover (≥70%) forest. Reproduction was negatively associated with the area of medium-intensity timber harvests characteristic of proposed fuel treatments. Our results also suggested that the amount of edge between older forests and shrub/sapling vegetation and increased habitat heterogeneity may positively influence demographic rates of Spotted Owls. Finally, high-severity fire negatively influenced the probability of territory colonization. Despite correlations between owl demographic rates and several habitat variables, life stage simulation (sensitivity) analyses indicated that the amount of forest with high canopy cover was the primary driver of population growth and equilibrium occupancy at the scale of individual territories. Greater than 90% of medium-intensity harvests converted high-canopy-cover forests into lower-canopy-cover vegetation classes, suggesting that landscape-scale fuel treatments in such stands could have short-term negative impacts on populations of California Spotted Owls. Moreover, high-canopy-cover forests declined by an average of 7.4% across territories during our study, suggesting that habitat loss could have contributed to declines in abundance and territory occupancy. We recommend that managers consider the existing amount and spatial distribution of high-canopy forest before implementing fuel treatments within an owl territory, and that treatments be accompanied by a rigorous monitoring program.

Relation between occupancy and abundance for a territorial species, the California spotted owl.

Land and resource managers often use detection-nondetection surveys to monitor the populations of species that may be affected by factors such as habitat alteration, climate change, and biological invasions. Relative to mark-recapture studies, using detection-nondetection surveys is more cost-effective, and recent advances in statistical analyses allow the incorporation of detection probability, covariates, and multiple seasons. We examined the efficacy of using detection-nondetection data (relative to mark-recapture data) for monitoring population trends of a territorial species, the California Spotted Owl (Strix occidentalis occidentalis). We estimated and compared the finite annual rates of population change (λt ) and the resulting realized population change (Δt ) from both occupancy and mark-recapture data collected over 18 years (1993-2010). We used multiseason, robust-design occupancy models to estimate that territory occupancy declined during our study (Δt = 0.702, 95% CI 0.552-0.852) due to increasing territory extinction rates (ε(1993) = 0.019 [SE 0.012]; ε(2009) = 0.134 [SE 0.043]) and decreasing colonization rates (γ(1993) = 0.323 [SE 0.124]; γ(2009) = 0.242 [SE 0.058]). We used Pradel's temporal-symmetry model for mark-recapture data to estimate that the population trajectory closely matched the trends in territory occupancy (Δt = 0.725, 95% CI 0.445-1.004). Individual survival was constant during our study (φ(1993) = 0.816 [SE 0.020]; φ(2009) = 0.815 [SE 0.019]), whereas recruitment declined slightly (f(1993) = 0.195 [SE 0.032]; f(2009) = 0.160 [SE 0.023]). Thus, we concluded that detection-nondetection data can provide reliable inferences on population trends, especially when funds preclude more intensive mark-recapture studies.

A flexible Bayesian hierarchical approach for analyzing spatial and temporal variation in the fecal corticosterone levels in birds when there is imperfect knowledge of individual identity.

Population cycles have long interested biologists. The ruffed grouse, Bonasa umbellus, is one such species whose populations cycle over most of their range. Thus, much effort has been expended to understand the mechanisms that might control cycles in this and other species. Corticosterone metabolites are widely used in studies of animals to measure physiological stress. We evaluated corticosterone metabolites in feces of territorial male grouse as a potential tool to study mechanisms governing grouse cycles. However, like most studies of corticosterone in wild animals, we did not know the identity of all individuals for which we had fecal samples. This presented an analytical problem that resulted in either pseudoreplication or confounding. Therefore, we derived an analytical approach that accommodated for uncertainty in individual identification. Because we had relatively low success capturing birds, we estimated turnover probabilities of birds on territorial display sites based on capture histories of a limited number of birds we captured. Hence, we developed a study design and modeling approach to quantify variation in corticosterone levels among individuals and through time that would be applicable to any field study of corticosterone in wild animals. Specifically, we wanted a sampling design and model that was flexible enough to partition variation among individuals, spatial units, and years, while incorporating environmental covariates that would represent potential mechanisms. We conducted our study during the decline phase of the grouse cycle and found high variation among corticosterone samples (11.33-443.92 ng/g [x=113.99 ng/g, SD=69.08, median=99.03 ng/g]). However, there were relatively small differences in corticosterone levels among years, but levels declined throughout each breeding season, which was opposite our predictions for stress hormones correlating with a declining population. We partitioned the residual variation into site, bird, and repetition (i.e., multiple samples collected from the same bird on the same day). After accounting for years and three general periods within breeding seasons, 42% of the residual variation among observations was attributable to differences among individual birds. Thus, we attribute little influence of site on stress level of birds in our study, but disentangling individual from site effects is difficult because site and bird are confounded. Our model structures provided analytical approaches for studying species having different ecologies. Our approach also demonstrates that even incomplete information on individual identity of birds within samples is useful for analyzing these types of data.

Linking robust spatiotemporal datasets to assess and monitor habitat attributes of a threatened species.

Accessibility of multispectral, multitemporal imagery combined with recent advances in cloud computing and machine learning approaches have enhanced our ability to model habitat characteristics across broad spatial and temporal scales. We integrated a large dataset of known nest and roost sites of a threatened species, the Mexican spotted owl (Strix occidentalis lucida), in the southwestern USA with Landsat imagery processed using the Continuous Change Detection and Classification (CCDC) time series algorithm on Google Earth Engine. We then used maximum entropy modeling (Maxent) to classify the landscape into four 'spectral similarity' classes that reflected the degree to which 30-m pixels contained a multispectral signature similar to that found at known owl nest/roost sites and mapped spectral similarity classes from 1986-2020. For map interpretation, we used nationally consistent forest inventory data to evaluate the structural and compositional characteristics of each spectral similarity class. We found a monotonic increase of structural characteristics typically associated with owl nesting and roosting over classes of increasing similarity, with the 'very similar' class meeting or exceeding published minimum desired management conditions for owl nesting and roosting. We also found an increased rate of loss of forest vegetation typical of owl nesting and roosting since the beginning of the 21st century that can be partly attributed to increased frequency and extent of large (≥400 ha) wildfires. This loss resulted in a 38% reduction over the 35-year study period in forest vegetation most similar to that used for owl nesting and roosting. Our modelling approach using cloud computing with time series of Landsat imagery provided a cost-effective tool for landscape-scale, multidecadal monitoring of vegetative components of a threatened species' habitat. Our approach could be used to monitor trends in the vegetation favored by any other species, provided that high-quality location data such as we presented here are available.

Modeling species occurrence dynamics with multiple states and imperfect detection.

Recent extensions of occupancy modeling have focused not only on the distribution of species over space, but also on additional state variables (e.g., reproducing or not, with or without disease organisms, relative abundance categories) that provide extra information about occupied sites. These biologist-driven extensions are characterized by ambiguity in both species presence and correct state classification, caused by imperfect detection. We first show the relationships between independently published approaches to the modeling of multistate occupancy. We then extend the pattern-based modeling to the case of sampling over multiple seasons or years in order to estimate state transition probabilities associated with system dynamics. The methodology and its potential for addressing relevant ecological questions are demonstrated using both maximum likelihood (occupancy and successful reproduction dynamics of California Spotted Owl) and Markov chain Monte Carlo estimation approaches (changes in relative abundance of green frogs in Maryland). Just as multistate capture-recapture modeling has revolutionized the study of individual marked animals, we believe that multistate occupancy modeling will dramatically increase our ability to address interesting questions about ecological processes underlying population-level dynamics.

Occupancy estimation and modeling with multiple states and state uncertainty.

The distribution of a species over space is of central interest in ecology, but species occurrence does not provide all of the information needed to characterize either the well-being of a population or the suitability of occupied habitat. Recent methodological development has focused on drawing inferences about species occurrence in the face of imperfect detection. Here we extend those methods by characterizing occupied locations by some additional state variable (e.g., as producing young or not). Our modeling approach deals with both detection probabilities <1 and uncertainty in state classification. We then use the approach with occupancy and reproductive rate data from California Spotted Owls (Strix occidentalis occidentalis) collected in the central Sierra Nevada during the breeding season of 2004 to illustrate the utility of the modeling approach. Estimates of owl reproductive rate were larger than naïve estimates, indicating the importance of appropriately accounting for uncertainty in detection and state classification.

Don't forget to look down - collaborative approaches to predator conservation.

Finding effective ways of conserving large carnivores is widely recognised as a priority in conservation. However, there is disagreement about the most effective way to do this, with some favouring top-down 'command and control' approaches and others favouring collaboration. Arguments for coercive top-down approaches have been presented elsewhere; here we present arguments for collaboration. In many parts of the developed world, flexibility of approach is built into the legislation, so that conservation objectives are balanced with other legitimate goals. In the developing world, limited resources, poverty and weak governance mean that collaborative approaches are likely to play a particularly important part in carnivore conservation. In general, coercive policies may lead to the deterioration of political legitimacy and potentially to non-compliance issues such as illegal killing, whereas collaborative approaches may lead to psychological ownership, enhanced trust, learning, and better social outcomes. Sustainable hunting/trapping plays a crucial part in the conservation and management of many large carnivores. There are many different models for how to conserve carnivores effectively across the world, research is now required to reduce uncertainty and examine the effectiveness of these approaches in different contexts.

Using Search Time and Regression to Estimate Abundance of Territorial Spotted Owls.

Using conventional sampling methods, unbiased, precise estimates of the number of individuals in a population can be difficult to obtain for rare, secretive species. We used a Leslie regression model (ARM) to estimate the number (N0 ) and the variance of the number (V[N0 ]) of adult and subadult Northern Spotted Owls in a territorial population from direct counts within a 292 km2 study area. Estimates of N0 from day counts were more accurate and precise and more robust to fluctuations in survey effort than estimates from night counts. ARM estimates from day counts were not significantly different from two different maximum-likelihood estimates and required 30-64% less effort. These findings suggest a less costly method for statistically comparing Spotted Owl abundance between spatial or temporal units.

Ecomorphological relationships of a guild of ground-foraging birds in northern California, USA.

We studied habitat and morphological relationships of nine species of birds comprising a groundforaging guild within four distinct locations in northern California. Although the nine species overlapped extensively in habitat use, we observed subtle differences among species in specific characteristics of the habitats they used. About 40% of all cases were classified to the correct species based on a discriminant analysis (DA) of habitats across all study areas. Classification success from DAs on habitats within study areas ranged from 42 to 66%. Morphologies of species differed to varying degrees as 91% of all cases were classified to correct species by a DA of morphological variables. This morphological separation suggested that each species used different modes of obtaining resources. We found only weak relationships between habitat use and morphology. Morphology predicted from 13.6 to 19.0% of the variation in habitat use within each study area and only 13.9% of the habitat variation across all study areas. Habitat predicted from 6.2 to 14.6% of the morphological variation within each study area and 6.9% across all study areas. We suggest that complimentary relationships of habitat and morphology enabled species within this guild to use unique sets of resources.

Hematozoa from the spotted owl.

One hundred five spotted owls (Strix occidentalis) from seven populations and three subspecies were examined for hematozoa. Haemoproteus noctuae, H. syrnii, Leucocytozoon ziemanni, Trypanosoma avium, Atoxoplasma sp. and unidentified microfilariae were recorded. All northern (S. occidentalis caurina), California (S. occidentalis occidentalis) and Mexican (S. occidentalis lucida) spotted owls were infected with at least one hematozoan; 79% had multiple infections. Twenty-two percent of the owls were infected with as many as four species of parasites. There were significant differences in the prevalence of these species of parasites occurring among the five populations of northern and California spotted owls sampled in California. Haemoproteus noctuae, H. syrnii and Atoxoplasma sp. represented new host records for this host species.

The coccidia of quail in the United States.

Intestinal contents from 12 scaled quail (Callipepla squamata), 10 bobwhite quail (Colinus virginianus), 20 harlequin quail (Cyrtonyx montezumae), 35 California quail (Lophortyx californicus), 15 Gambel's quail (Lophortyx gambelii), and 29 mountain quail (Oreortyx pictus) were examined for coccidian oocysts. Only 18 (14.9%) of 121 birds had coccidian oocysts in their feces at the time of collection; these included 9 L. californicus and 9 O. pictus. Four eimerians and an isosporan were found in the 18 infected birds. Eimeria lophortygis and E. okanaganensis had been previously described from L. californicus, but were also seen in O. pictus. Eimeria crusti sp. n. and Eimeria oreortygis sp. n. are described from O. pictus; E. oreortygis was also found in L. californicus. Broadly ellipsoid oocysts of E. crusti had a rough outer wall, were 26.0 X 21.2 (24-28 X 20-23) microns, and contained ovoid sporocysts 15.7 X 7.5 (14-18 X 7-8)microns. Micropyle and oocyst residuum were absent but a polar granule, sporocyst residuum, Stieda and substieda bodies were present. Slightly ovoid oocysts of E. oreortygis had a smooth outer wall, were 24.4 X 18.7 (21-28 X 17-23) microns, and contained ovoid sporocysts 14.1 X 7.21 (13-16 X 6-9) microns. Micropyle and polar granules were absent but a small oocyst residuum, large sporocyst residuum, Stieda and substieda bodies were present. Oocysts of an isosporan were found and compared to oocysts of Isospora lacazei isolated from sparrows in a previous study.

Acute Chagas' cardiopathy in a polar bear (Ursus maritimus) in Guadalajara, Mexico.

We report a 24-year-old female polar bear (Ursus maritimus) who contracted Chagas' infection at the Guadalajara Zoo, in Jalisco, México, and died of acute Chagas' carditis 15 days later. The histopathological findings are described, as well as the presence of triatomids (Triatoma longipennis Usinger) infected with Trypanosoma cruzi collected within 5 meters from the place where the animal lived in the city of Guadalajara.

[Horseshoe kidney, stone disease and prostate cancer: a case presentation]. / Riñón en herradura, enfermedad litiásica y adenocarcinoma de próstata. Presentación de un caso clínico.

The horseshoe kidney is the most common congenital renal fusion anomalies. It occurs in 0.25% of the population, or 1 in every 400 people. It is more frequent in males (ratio 2:1). The most observed complication of horseshoe kidney is stone disease, although there may be others such as, abdominal pain, urinary infections, haematuria, hydronephrosis, trauma and tumours (most commonly associated with hypernephroma and Wilms tumour). We describe a case of a male patient with horseshoe kidney, stone disease and adenocarcinoma of the prostate. One carrier of this condition who suffered a transitional cell carcinoma of the prostate was found in a review of the literature.

[Mucosecretor adenocarcinoma of the lung with pleural involvement presenting as a pneumothorax. Presentation of a clinical case]. / Adenocarcinoma mucosecretor de pulmón con diseminación pleural que se manifiesta con neumotórax. Presentación de un caso clínico.

The combination of a pneumothorax and lung cancer is rare and diagnosis is complex. Clinical suspicion of cancer must be based on radiological findings and the existence of risk factors. We discuss the mechanisms involved in the development of pneumothorax in patients with lung cancer, as well as the clinical significance, the recommended diagnostic approach, and therapeutic guidelines.

Understanding and managing conservation conflicts.

Conservation conflicts are increasing and need to be managed to minimise negative impacts on biodiversity, human livelihoods, and human well-being. Here, we explore strategies and case studies that highlight the long-term, dynamic nature of conflicts and the challenges to their management. Conflict management requires parties to recognise problems as shared ones, and engage with clear goals, a transparent evidence base, and an awareness of trade-offs. We hypothesise that conservation outcomes will be less durable when conservationists assert their interests to the detriment of others. Effective conflict management and long-term conservation benefit will be enhanced by better integration of the underpinning social context with the material impacts and evaluation of the efficacy of alternative conflict management approaches.

[Stage IV stenosing sqamous cell carcinoma of the oesopahgus in a 41 year-old woman. A case presentation]. / Carcinoma epidermoide de esófago, estenosante, estadio IV, en mujer de 41 años. Descripción de un caso clínico.

OBJECTIVE: To present a clinical case of a 41 year-old woman, with a stage IV squamous cell carcinoma of the oesophagus. METHODS AND PATIENTS: We present a clinical case of 41 year-old woman with a history of type 2 diabetes mellitus, and resection of a haemosiderin plaque on the tongue. A space occupying lesion (SOL) was studied using ultrasound and Nuclear Magnetic Resonance (NMR), detecting, but unable to differentiate, a gradually increasing haemangioma or hepatocarcinoma. She was seen at the clinic due to dysphagia and loss of weight. In oesophagogastroscopy with biopsy a squamous cell carcinoma of the oesophagus was diagnosed. The Computed Tomography (CT) of the neck, thorax and abdomen showed a stenosing tumour in the oesophagus with metastasis in the lungs and left adrenal gland, and a SOL in the liver compatible with a neo-formative process. The erythrocyte sedimentation rate was 55 mm. She was referred to Surgery and Oncology, who performed a gastrostomy for enteral feeding and started treatment with palliative chemotherapy. CONCLUSIONS: Squamous cell carcinoma of the oesophagus is very frequent. The two most important risk factors are alcoholism and nicotine poisoning. The dysphagia is the most common symptom (96% of the patients). The prognosis is a poor, with high mortality. Surgery is the standard treatment when the tumour is located. Chemotherapy and radiotherapy are palliative treatments, but has not shown to be very effective.

Potential influences of climate and nest structure on spotted owl reproductive success: a biophysical approach.

Many bird species do not make their own nests; therefore, selection of existing sites that provide adequate microclimates is critical. This is particularly true for owls in north temperate climates that often nest early in the year when inclement weather is common. Spotted owls use three main types of nest structures, each of which are structurally distinct and may provide varying levels of protection to the eggs or young. We tested the hypothesis that spotted owl nest configuration influences nest microclimate using both experimental and observational data. We used a wind tunnel to estimate the convective heat transfer coefficient (h(c)) of eggs in 25 potential nest configurations that mimicked 2 nest types (top-cavity and platform nests), at 3 different wind speeds. We then used the estimates of h(c) in a biophysical heat transfer model to estimate how long it would take unattended eggs to cool from incubation temperature (~36 °C) to physiological zero temperature (PZT; ~26 °C) under natural environmental conditions. Our results indicated that the structural configuration of nests influences the cooling time of the eggs inside those nests, and hence, influences the nest microclimate. Estimates of time to PZT ranged from 10.6 minutes to 33.3 minutes. Nest configurations that were most similar to platform nests always had the fastest egg cooling times, suggesting that platform nests were the least protective of those nests we tested. Our field data coupled with our experimental results suggested that nest choice is important for the reproductive success of owls during years of inclement weather or in regions characterized by inclement weather during the nesting season.

Sources of variability in spotted owl population growth rate: testing predictions using long-term mark-recapture data.

For long-lived iteroparous vertebrates that annually produce few young, life history theory predicts that reproductive output (R) and juvenile survival should influence temporal variation in population growth rate (lambda) more than adult survival does. We examined this general prediction using 15 years of mark-recapture data from a population of California spotted owls (Strix occidentalis occidentalis). We found that survival of individuals > or =1 year old (phi) exhibited much less temporal variability (CV = 0.04), where CV is coefficient of variation, than R (CV = 0.83) and that R was strongly influenced by environmental stochasticity. Although lambda was most sensitive (ê; log-transformed sensitivity) to phi (ê = 0.77), and much less sensitive to either R (ê = 0.12) or juvenile survival (survival rate of owls from fledging to 1 year old; ê = 0.12), we estimated that R contributed as much as phi to the observed annual variability in lambda. The contribution of juvenile survival to variability in lambda was proportional to its ê. These results are consistent with the hypothesis that natural selection may have favored the evolution of longevity in spotted owls as a strategy to increase the probability of experiencing favorable years for reproduction. Our finding that annual weather patterns that most affected R (temperature and precipitation during incubation) and phi (conditions during winter related to the Southern Oscillation Index) were equally good at explaining temporal variability in lambda supports the conclusion that R and phi were equally responsible for variability in lambda. Although currently accepted conservation measures for spotted owl populations attempt to enhance survival, our results indicated that conservation measures that target R may be as successful, as long as actions do not reduce phi.