Supplemental structured surveys and pre-existing detection models improve fine-scale density and population estimation with opportunistic community science data.

Density and population estimates aid in conservation and stakeholder communication. While free and broadly available community science data can effectively inform species distribution models, they often lack the information necessary to estimate imperfect detection and area sampled, thus limiting their use in fine-scale density modeling. We used structured distance-sampling surveys to model detection probability and calculate survey-specific detection offsets in community science models. We estimated density and population for 16 songbird species under three frameworks: (1) a fixed framework that assumes perfect detection within a specified survey radius, (2) an independent framework that calculates offsets from an independent source, and (3) a calibration framework that calculates offsets from supplemental surveys. Within the calibration framework, we examined the effects of calibration dataset size and data pooling. Estimates of density and population size were consistently biased low in the fixed framework. The independent and calibration frameworks produced reliable estimates for some species, but biased estimates for others, indicating discrepancies in detection probability between structured and community science surveys. The calibration framework produced reliable population estimates with as few as 10 calibration surveys with positive detections. Data pooling dramatically decreased bias. This study provides conservationists and managers with a cost-effective method of estimating density and population.

Isolating the Role of Corticosterone in the Hypothalamic-Pituitary-Gonadal Transcriptomic Stress Response.

Investigation of the negative impacts of stress on reproduction has largely centered around the effects of the adrenal steroid hormone, corticosterone (CORT), and its influence on a system of tissues vital for reproduction-the hypothalamus of the brain, the pituitary gland, and the gonads (the HPG axis). Research on the action of CORT on the HPG axis has predominated the stress and reproductive biology literature, potentially overshadowing other influential mediators. To gain a more complete understanding of how elevated CORT affects transcriptomic activity of the HPG axis, we experimentally examined its role in male and female rock doves (Columba livia). We exogenously administrated CORT to mimic circulating levels during the stress response, specifically 30 min of restraint stress, an experimental paradigm known to increase circulating CORT in vertebrates. We examined all changes in transcription within each level of the HPG axis as compared to both restraint-stressed birds and vehicle-injected controls. We also investigated the differential transcriptomic response to CORT and restraint-stress in each sex. We report causal and sex-specific effects of CORT on the HPG transcriptomic stress response. Restraint stress caused 1567 genes to uniquely differentially express while elevated circulating CORT was responsible for the differential expression of 304 genes. Only 108 genes in females and 8 in males differentially expressed in subjects that underwent restraint stress and those who were given exogenous CORT. In response to elevated CORT and restraint-stress, both sexes shared the differential expression of 5 genes, KCNJ5, CISH, PTGER3, CEBPD, and ZBTB16, all located in the pituitary. The known functions of these genes suggest potential influence of elevated CORT on immune function and prolactin synthesis. Gene expression unique to each sex indicated that elevated CORT affected more gene transcription in females than males (78 genes versus 3 genes, respectively). To our knowledge, this is the first study to isolate the role of CORT in HPG genomic transcription during a stress response. We present an extensive and openly accessible view of the role corticosterone in the HPG transcriptomic stress response. Because the HPG system is well conserved across vertebrates, these data have the potential to inspire new therapeutic strategies for reproductive dysregulation in multiple vertebrate systems, including our own.

The influence of rare birds on observer effort and subsequent rarity discovery in the American birdwatching community.

Birdwatching is a rapidly growing pastime, increasingly involving the pursuit of rare birds as birders build lists of species they encounter. We expected reports of rare bird discoveries to quickly draw birders to locations, and that the increased attention at those locations would decay over time. We hypothesized that magnitude of draw and rates of decay would vary depending on characteristics of the species and the geographic locations where rarities were discovered. Discoveries of additional rarities might affect both the draw and decay, so we also quantified empirical evidence for the Patagonia Picnic Table Effect (PPTE), a social feedback loop where rarity discoveries are presumed to lead to additional rarity discoveries because of the elevated levels of birder activity once an initial rarity is reported. Although commonly invoked, supporting evidence for the PPTE hypothesis is anecdotal. We used 10 years of eBird data (2008-2017) in the United States to (1) understand birding activity when rarities were reported and the factors associated with draw and decay, and (2) assess the frequency at which initial rarity discoveries lead to reports of additional rarities. Across 273 rarity events, birder effort, as indexed by numbers of eBird checklists, increased above the pre-event baseline level, with the magnitude of draw varying geographically. We found no indication that draw was influenced by species identity or rarity-level, but latitude and distance to small airport proved important in drawing additional eBirders to rare bird discoveries. Mean draw of rarities and mean number of checklists from the same locations prior to each rarity discovery grew through the ten years, suggesting an increased influence of eBird on birder behavior in general. Decay rates in birder effort were more gradual in rare bird events with longer durations. Effort declined below baseline-levels after rarities went undetected, suggesting, "location-fatigue" following rarity events. Results did not support the PPTE hypothesis. Controlling for site-specific circumstances, birders had no better chance of finding additional rarities during events than at times outside events. Our results emphasize that eBird checklist quantity at rarity events follows a predictable but variable pattern of draw and decay influenced by location and time since rarity discovery; that birders have statistically similar chances of finding rarities during normal "baseline" birding activities as they do when known rarities are present; and that eBird represents a largely untapped resource for studying factors that influence levels of birding activity.

Building a better baseline to estimate 160 years of avian population change and create historically informed conservation targets.

Globally, anthropogenic land-cover change has been dramatic over the last few centuries and is frequently invoked as a major cause of wildlife population declines. Baseline data currently used to assess population trends, however, began well after major changes to the landscape. In the United States and Canada, breeding bird population trends are assessed by the North American Breeding Bird Survey, which began in the 1960s. Estimates of distribution and abundance prior to major habitat alteration would add historical perspective to contemporary trends and allow for historically based conservation targets. We used a hindcasting framework to estimate change in distribution and abundance of 7 bird species in the Willamette Valley, Oregon (United States). After reconciling classification schemes of current and 1850s reconstructed land cover, we used multiscale species distribution models and hierarchical distance sampling models to predict spatially explicit densities in the modern and historical landscapes. We estimated that since the 1850s, White-breasted Nuthatch (Sitta carolinensis) and Western Meadowlark (Sturnella neglecta) populations, 2 species sensitive to fragmentation of oak woodlands and grasslands, declined by 93% and 97%, respectively. Five other species we estimated nearly stable or increasing populations, despite steep regional declines since the 1960s. Based on these estimates, we developed historically based conservation targets for amount of habitat, population, and density for each species. Hindcasted reconstructions provide historical perspective for assessing contemporary trends and allow for historically based conservation targets that can inform current management.

Construcción de una Mejor Línea Base para Estimar 160 Años de Cambio en la Población de Aves y Crear Objetivos de Conservación Orientados Históricamente Resumen A nivel mundial, el cambio antropogénico en la cobertura del suelo ha sido dramático durante los últimos siglos y frecuentemente se le considera una de las principales causas de las declinaciones en la población de fauna. A pesar de esto, se comenzó a registrar los datos de línea base que se usan actualmente para evaluar las tendencias poblacionales mucho después de cambios importantes en el paisaje. En los Estados Unidos de América y en Canadá, las tendencias poblacionales de las aves reproductoras se evalúan por medio del Censo de Aves Reproductoras, el cual comenzó en la década de 1960. Los estimados de la distribución y abundancia previas a las alteraciones importantes en el hábitat le proporcionarían a este censo una perspectiva histórica de las tendencias contemporáneas y permitirían el establecimiento de objetivos de conservación con fundamentos históricos. Usamos un marco de trabajo de análisis retrospectivo para estimar el cambio en la distribución y abundancia de siete especies de aves en el Valle Willamette en Oregon (E.U.A). Después de reconciliar los esquemas de clasificación de la cobertura de suelo actual y la reconstruida para la década de 1850, usamos modelos multiescala de distribución de especies y modelos de muestreo de distancia jerárquica para predecir las densidades espacialmente explícitas en los paisajes históricos y modernos. Estimamos que las poblaciones de Sitta carolinensis y Sturnella neglecta, dos poblaciones sensibles a la fragmentación de los bosques de roble y de los pastizales, han declinado en un 93% y 97% desde la década de 1850, respectivamente. Otras cinco especies han tenido poblaciones casi estables o en crecimiento, a pesar de las declinaciones abruptas desde la década de 1960. Las reconstrucciones por medio de análisis retrospectivos proporcionan una perspectiva histórica para la evaluación de las tendencias contemporáneas y permiten el establecimiento de objetivos con bases históricas que pueden orientar al manejo que ocurre hoy en día.

Idiosyncratic changes in spring arrival dates of Pacific Northwest migratory birds.

Shifts in the timing of bird migration have been associated with climatic change and species traits. However, climatic change does not affect all species or geographic locations equally. Climate in the Pacific Northwest has shifted during the last century with mean temperatures increasing by 1 °C but little change in total annual precipitation. Few long-term data on migration phenology of birds are available in the Pacific Northwest. We analyzed trends in spring arrival dates from a site in the Oregon Coast Range where nearly daily inventories of birds were conducted in 24 of 29 years. Several species showed statistically significant shifts in timing of first spring arrivals. Six of 18 species occur significantly earlier now than during the initial phase of the study. One species arrives significantly later. Eleven show no significant shifts in timing. We associated trends in spring migration phenology with regional climatic variables, weather (precipitation and temperature), traits of species such as migration strategy, foraging behavior, diet, and habitat use, and regional trends in abundance as indexed by Breeding Bird Survey data. We found no set of variables consistently correlated with avian phenological changes. Post hoc analyses of additional climate variables revealed an association of migratory arrival dates across the 18 species with rainfall totals in northern California, presumably indicating that songbird arrival dates in Oregon are slowed by spring storm systems in California. When only the six species with the most strongly advancing arrival dates were analyzed, winter maximum temperatures in the preceding three winters appeared consistently in top models, suggesting a possible role for food availability early in spring to promote the survival and successful reproduction of the earliest-arriving birds. However, additional data on food availability and avian survival and reproductive success are required to test that hypothesis. Despite the appearance of some climate variables in top models, there remains a mismatch between strongly advancing arrival dates in some songbirds and a lack of clear directional change in those climate variables. We conclude that either some previously unrecognized variable or combination of variables has affected the timing of migration in some species but not others, or the appearance of statistically significant directional changes over time can occur without being driven by consistent environmental or species-specific factors.

Metal-mediated climate susceptibility in a warming world: Larval and latent effects on a model amphibian.

Although sophisticated models predict the effects of future temperatures on ectotherms, few also address how ubiquitous sublethal contaminants alter an organism's response to thermal stress. In ectotherms, higher metabolic rates from warming temperatures can beneficially speed metabolism and development. If compounded by chronic, sublethal pollution, additional resource demands for elimination or detoxification may limit their ability to cope with rising temperatures-the toxicant-induced climate susceptibility hypothesis. In outdoor bioassays, using natural lake water as the background, the authors investigated the development of a model ectotherm in 6 levels of Cd, Cu, and Pb mixtures and 3 thermal regimes of diel temperature fluctuations: ambient, +1.5 °C, and +2.5 °C. Warming had no effect on wild-caught Cope's gray tree frog (Hyla chrysoscelis) until metals concentrations were approximately 10-fold of their bioavailable chronic criterion unit (sums of bioavailable fractions of chronic criteria concentrations). In treatments with ≥10 bioavailable chronic criterion units and +1.5 °C, growth increased. Conversely, in treatments with 28 bioavailable chronic criterion units and maximal +2.5 °C warming, growth declined and the body condition of postmetamorphic juveniles at 20 d was 34% lower than that of juveniles from background conditions (lake water at ambient temperatures). These findings suggest toxicant-induced climate susceptibility with long-term latent effects on the juvenile life stage. Sublethal contaminants can intensify the impact on aquatic ectotherms at the most conservative levels of predicted global warming over the next century. Environ Toxicol Chem 2016;35:1872-1882. © 2015 SETAC.

The deal with diel: Temperature fluctuations, asymmetrical warming, and ubiquitous metals contaminants.

Climate projections over the next century include disproportionately warmer nighttime temperatures ("asymmetrical warming"). Cool nighttime temperatures lower metabolic rates of aquatic ectotherms. In contaminated waters, areas with cool nights may provide thermal refugia from high rates of daytime contaminant uptake. We exposed Cope's gray tree frogs (Hyla chrysoscelis), southern leopard frogs (Lithobates sphenocephalus), and spotted salamanders (Ambystoma maculatum) to five concentrations of a mixture of cadmium, copper, and lead under three to four temperature regimes, representing asymmetrical warming. At concentrations with intermediate toxicosis at test termination (96 h), temperature effects on acute toxicity or escape distance were evident in all study species. Asymmetrical warming (day:night, 22:20 °C; 22:22 °C) doubled or tripled mortality relative to overall cooler temperatures (20:20 °C) or cool nights (22:18 °C). Escape distances were 40-70% shorter under asymmetrical warming. Results suggest potentially grave ecological impacts from unexpected toxicosis under climate change.