Collapse of a desert bird community over the past century driven by climate change

R. M, Mukherjee S, Robin VV. Playback-Aided Surveys and Acoustic Monitoring in the Detection of the Endangered Forest Owlet Athene blewitti

Monitoring rare and endangered species over the long term is challenging due to limited historical data and comparable methods. Climate and landscape changes can significantly impact species distributions, driving some to extinction. The Forest Owlet is an endangered bird considered extinct but rediscovered after 113 years in 1997. Since its rediscovery, followed by the description of its calls, there have been regular recent sightings of the species from newer locations, leading to its downlisting in the IUCN Red List from critically endangered to endangered. In the Dang region in Gujarat, India, there have been no historical records despite previous systematic ornithological studies over three decades, but have multiple sightings over the last few years. Although we now know a little more about the broad association of the species occurrence with habitat and climate variables, a major focus of this study is to estimate the reasons for the "appearance" of the Forest Owlet in Dangs. We revisited locations of past surveys to determine if the species is currently found in the study sites where it was previously unrecorded. We also examine whether new survey methods using playback of its call could enhance its detection. During resurveys, we located the Forest Owlet at new, previously unrecorded locations. Analyses of satellite imagery products revealed significant changes in the broader Dang landscape, including the loss of native forests, increased agriculture, and shifts in mean maximum temperature and rainfall. Our research suggests playback can enhance detection, although its effectiveness varies across landscapes. A detection strategy for long-term monitoring was developed using different acoustic detectors. An effective detection distance of 300 m within the habitat was achieved using automated recording units (ARUs). Although the species responds to climate and habitat change, the cause of the increased reports of this endangered species remains undetermined. However, we found increased detections using newer survey techniques involving bioacoustics. We recommend using these techniques carefully for future baseline studies, which are urgently required.

Modeling Population Growth under Climate Stressors Using Age-Structured Matrix Models

Climate resilience, a focus of many recent studies, has been examined from ecological, physiological, and evolutionary perspectives. However, sampling biases toward adults, males, and certain species have made establishing the link between environmental change and population-level change problematic. Here, we used data from four laboratory studies, in which we administered pre- and postnatal stressors, such as suboptimal incubation temperature, heat stress, and food restriction, to zebra finches. We then quantified hatching success, posthatch survival, and reproductive success, to parameterize age-structured population dynamics models with the goal of estimating the effect of the stressors on relative population growth rates. Using the same model structure, we tested the hypothesis that early life stages influence population growth rate more than later life stages. Our models suggested that stressful events during embryonic development, such as suboptimal incubation temperatures and reduced gas exchange for the embryos, have a greater total impact on population growth than posthatch stressors, such as heat stress and food restriction. However, among life history traits, differences in hatching success and sex ratio of offspring in response to stressors changed population growth rates more than differences in any other demographic rate estimates. These results suggest that when predicting population resilience against climate change, it is critical to account for effects of climate change on all life stages, including early stages of life, and to incorporate individuals' physiology and stress tolerance that likely influence future stress responses, reproduction, and survival.

Large carpenter bees show high dispersal in a tropical semi-arid region susceptible to desertification

Desertification is a major threat to biodiversity in arid areas of the world, partly because many organisms in these regions already exist at or near the limits of their movement and physiology. Here, we used molecular data to investigate patterns of persistence and dispersal in an ecologically and economically important carpenter bee (Xylocopa grisescens Lepeletier) found throughout the semiarid Caatinga region of Brazil. We used a genome-wide approach (double digest restriction-site associated DNA, ddRAD) to gather genetic data from bees sampled from eight sites within a semiarid region subject to desertification in Northeastern Brazil. Across all populations, we observed a consistent heterozygosity and effective population size deficit along with low genetic differentiation. We did not find strong evidence of dispersal limitations caused by desertification in this study system despite data collection from sites up to 300 km distant. Thus, our data suggest that human-mediated changes in the Caatinga, such as habitat loss, have impacted the population genetic patterns of X. grisescens. However, these impacts have also been softened by the species' biological characteristics, such as its relatively high capacity for movement. This study provides insights into how habitat changes might impact the long-term survival of large solitary bees.

Arctos: Community-driven innovations for managing natural and cultural history collections

More than tools for managing physical and digital objects, museum collection management systems (CMS) serve as platforms for structuring, integrating, and making accessible the rich data embodied by natural history collections. Here we describe Arctos, a scalable community solution for managing and publishing global biological, geological, and cultural collections data for research and education. Specific goals are to: (1) Describe the core features and implementation of Arctos for a broad audience with respect to the biodiversity informatics principles that enable high quality research; (2) Highlight the unique aspects of Arctos; (3) Illustrate Arctos as a model for supporting and enhancing the Digital Extended Specimen concept; and (4) Emphasize the role of the Arctos community for improving data discovery and enabling cross-disciplinary, integrative studies within a sustainable governance model. In addition to detailing Arctos as both a community of museum professionals and a collection database platform, we discuss how Arctos achieves its richly annotated data by creating a web of knowledge with deep connections between catalog records and derived or associated data. We also highlight the value of Arctos as an educational resource. Finally, we present the financial model of fiscal sponsorship by a nonprofit organization, implemented in 2022, to ensure the long-term success and sustainability of Arctos.

Variation in water utilization by mammal diversity in Khao Phaeng Ma Non-hunting area, Thailand

Access to suitable water sources is important for mammals. This study aimed to compared mammal diversity and water use among water springs, standard artificial ponds, and water pans within the Khao Phaeng Ma Non-Hunting Area in 2020 and 2021. Two camera traps were installed at each water sources for 749 nights with a total of 12 camera traps of 6 water sources. A total of 19,467 photographs were recorded comprising 13,777 photographs of gaur (Bos gaurus, vulnerable and the most important species in the area), and 5690 photographs of other mammals. In the wet season, relative use was highest at standard artificial pond number 2, which is established in the forest plantation area (4 × 4 m spacing, 12-20 m height, and 60%-80 % crown cover) and has a high volume of water, and at water pan number 1, which mimics a natural water spring in the man-made grassland and can supply water to mammals throughout the year. In the dry seasons, relative use was highest at water pan numbers 1 and 2; at the same time, other water sources dried up. During the study period, the number of mammal species was highest at water pan number 1 (10 species, diversity index [H'] = 1.38), and water pan number 2 (11 species, H' = 1.75). Grazers and browsers, including gaur, sambar deer (Rusa unicolor), northern red muntjac (Muntiacus vaginalis), omnivores (e.g. wild boar, Sus scrofa), and Asian black bear (Ursus thibetanus), used the water pan in the artificial grassland and standard artificial pond in the forest plantation rather than the water spring in the dry evergreen forest. Beside forest types, the use of water springs was associated with water period (months), while the use of standard artificial pond and water pans was associated with water surface area, water depth, altitude, species diversity, and species richness, and number of mammals photographed. The results show that water pans were more suitable for utilization by mammals than are other water sources.

State-dependent movement choices of desert lizards: The role of behavioural thermoregulation during summer and winter

Environmental temperatures are increasing worldwide, threatening desert ectotherms already living at their thermal limits. Organisms with flexible thermoregulatory behaviours may be able to mitigate the effects of extreme temperatures by moving among microhabitats, yet little work has tracked movement patterns of desert ectotherms in the wild over diurnal scales or compared behaviour among seasons. Here, we used camera traps to track the thermoregulatory behaviour and microhabitat choices of 30 desert lizards (Messalina bahaldini) in custom, outdoor arenas that provided access to open, rock, and bush microhabitats. We found that in the summer, lizards preferred to move to the shaded microhabitats and remain there under warmer conditions. During winter, however, lizards' activity was not related to temperature, and lizards mostly chose to remain in the open habitat. Interestingly, in both seasons, lizards tended to remain in their current microhabitat and moved infrequently between certain combinations of microhabitats. Our study shows that thermoregulation (shade-seeking behaviour) is a major factor during summer, helping lizards to avoid extreme temperatures, but not during winter, and shows a novel effect of current microhabitat on movement, suggesting that other biotic or abiotic factors may also drive microhabitat choice. Understanding the complex factors at play in microhabitat choice is critical for developing conservation programs that effectively mitigate the negative impacts of climate change on desert animals.

The geographic extent of bird populations affected by renewable-energy development

Bird populations are declining globally. Wind and solar energy can reduce emissions of fossil fuels that drive anthropogenic climate change, yet renewable-energy production represents a potential threat to bird species. Surveys to assess potential effects at renewable-energy facilities are exclusively local, and the geographic extent encompassed by birds killed at these facilities is largely unknown, which creates challenges for minimizing and mitigating the population-level and cumulative effects of these fatalities. We performed geospatial analyses of stable hydrogen isotope data obtained from feathers of 871 individuals of 24 bird species found dead at solar- and wind-energy facilities in California (USA). Most species had individuals with a mix of origins, ranging from 23% to 98% nonlocal. Mean minimum distances to areas of likely origin for nonlocal individuals were as close as 97 to >1250 km, and these minimum distances were larger for species found at solar-energy facilities in deserts than at wind-energy facilities in grasslands (Cohen's d = 6.5). Fatalities were drawn from an estimated 30-100% of species' desingated ranges, and this percentage was significantly smaller for species with large ranges found at wind facilities (Pearson's r = -0.67). Temporal patterns in the geographic origin of fatalities suggested that migratory movements and nonmigratory movements, such as dispersal and nomadism, influence exposure to fatality risk for these birds. Our results illustrate the power of using stable isotope data to assess the geographic extent of renewable-energy fatalities on birds. As the buildout of renewable-energy facilities continues, accurate assessment of the geographic footprint of wildlife fatalities can be used to inform compensatory mitigation for their population-level and cumulative effects.

Potential extinction cascades in a desert ecosystem: Linking food web interactions to community viability

Desert communities are threatened with species loss due to climate change, and their resistance to such losses is unknown. We constructed a food web of the Mojave Desert terrestrial community (300 nodes, 4080 edges) to empirically examine the potential cascading effects of bird extinctions on this desert network, compared to losses of mammals and lizards. We focused on birds because they are already disappearing from the Mojave, and their relative thermal vulnerabilities are known. We quantified bottom-up secondary extinctions and evaluated the relative resistance of the community to losses of each vertebrate group. The impact of random bird species loss was relatively low compared to the consequences of mammal (causing the greatest number of cascading losses) or reptile loss, and birds were relatively less likely to be in trophic positions that could drive top-down effects in apparent competition and tri-tropic cascade motifs. An avian extinction cascade with year-long resident birds caused more secondary extinctions than the cascade involving all bird species for randomized ordered extinctions. Notably, we also found that relatively high interconnectivity among avian species has formed a subweb, enhancing network resistance to bird losses.

Assessing the global vulnerability of dryland birds to heatwaves

As global average surface temperature increases, extreme climatic events such as heatwaves are becoming more frequent and intense, which can drive biodiversity responses such as rapid population declines and/or shifts in species distributions and even local extirpations. However, the impacts of extreme climatic events are largely ignored in conservation plans. Birds are known to be susceptible to heatwaves, especially in dryland ecosystems. Understanding which birds are most vulnerable to heatwaves, and where these birds occur, can offer a scientific basis for adaptive management and conservation. We assessed the relative vulnerability of 1196 dryland bird species to heatwaves using a trait-based approach. Among them, 888 bird species are estimated to be vulnerable to heatwaves (170 highly vulnerable, eight extremely vulnerable), of which ~91% are currently considered non-threatened by the IUCN, which suggests that many species will likely become newly threatened with intensifying climate change. We identified the top three hotspot areas of heatwave-vulnerable species in Australia (208 species), Southern Africa (125 species) and Eastern Africa (99 species). Populations of vulnerable species recorded in the Living Planet Database were found to be declining significantly faster than those of non-vulnerable species (p = .048) after heatwaves occurred. In contrast, no significant difference in population trends between vulnerable and non-vulnerable species was detected when no heatwave occurred (p = .34). This suggests that our vulnerability framework correctly identified vulnerable species and that heatwaves are already impacting the population trends of these species. Our findings will help prioritize heatwave-vulnerable birds in dryland ecosystems in risk mitigation and adaptation management as the frequency of heatwaves accelerates in the coming decades.

A cloudy forecast for species distribution models: Predictive uncertainties abound for California birds after a century of climate and land-use change

Correlative species distribution models are widely used to quantify past shifts in ranges or communities, and to predict future outcomes under ongoing global change. Practitioners confront a wide range of potentially plausible models for ecological dynamics, but most specific applications only consider a narrow set. Here, we clarify that certain model structures can embed restrictive assumptions about key sources of forecast uncertainty into an analysis. To evaluate forecast uncertainties and our ability to explain community change, we fit and compared 39 candidate multi- or joint species occupancy models to avian incidence data collected at 320 sites across California during the early 20th century and resurveyed a century later. We found massive (>20,000 LOOIC) differences in within-time information criterion across models. Poorer fitting models omitting multivariate random effects predicted less variation in species richness changes and smaller contemporary communities, with considerable variation in predicted spatial patterns in richness changes across models. The top models suggested avian environmental associations changed across time, contemporary avian occupancy was influenced by previous site-specific occupancy states, and that both latent site variables and species associations with these variables also varied over time. Collectively, our results recapitulate that simplified model assumptions not only impact predictive fit but may mask important sources of forecast uncertainty and mischaracterize the current state of system understanding when seeking to describe or project community responses to global change. We recommend that researchers seeking to make long-term forecasts prioritize characterizing forecast uncertainty over seeking to present a single best guess. To do so reliably, we urge practitioners to employ models capable of characterizing the key sources of forecast uncertainty, where predictors, parameters and random effects may vary over time or further interact with previous occurrence states.

Protected area coverage of vulnerable regions to conserve functional diversity of birds

Global-change drivers are increasing the rates of species extinction worldwide, posing a serious threat to ecosystem functioning. Preserving the functional diversity of species is currently a priority to mitigate abrupt biodiversity loss in the coming decades. Therefore, understanding what factors better predict functional diversity loss in bird assemblages at a global scale and how existing protected areas cover the most vulnerable regions is of key importance for conservation. We examined the environmental factors associated with the risk of functional diversity loss under 3 scenarios of bird species extinction based on species distribution range size, generation length, and International Union for the Conservation of Nature conservation status. Then, we identified regions that deserve special conservation focus. We also assessed how efficiently extant terrestrial protected areas preserve particularly vulnerable bird assemblages based on predicted scenarios of extinction risk. The vulnerability of bird functional diversity increased as net primary productivity, land-use diversity, mean annual temperature, and elevation decreased. Low values for these environmental factors were associated with a higher risk of functional diversity loss worldwide through two mechanisms: one independent of species richness that affects assemblages with low levels of niche packing and high functional dissimilarity among species, and the other that affects assemblages with low species richness and high rates of extinction. Existing protected areas ineffectively safeguarded regions with a high risk of losing functional diversity in the next decades. The global predictors and the underlying mechanisms of functional vulnerability in bird assemblages we identified can inform strategies aimed at preserving bird-driven ecological functions worldwide.

Experimental nest cooling reveals dramatic effects of heatwaves on reproduction in a Mediterranean bird of prey

Future climatic scenarios forecast increases in average temperatures as well as in the frequency, duration, and intensity of extreme events, such as heatwaves. Whereas behavioral adjustments can buffer direct physiological and fitness costs of exposure to excessive temperature in wild animals, these may prove more difficult during specific life stages when vagility is reduced (e.g., early developmental stages). By means of a nest cooling experiment, we tested the effects of extreme temperatures on different stages of reproduction in a cavity-nesting Mediterranean bird of prey, the lesser kestrel (Falco naumanni), facing a recent increase in the frequency of heatwaves during its breeding season. Nest temperature in a group of nest boxes placed on roof terraces was reduced by shading them from direct sunlight in 2 consecutive years (2021 and 2022). We then compared hatching failure, mortality, and nestling morphology between shaded and non-shaded (control) nest boxes. Nest temperature in control nest boxes was on average 3.9°C higher than in shaded ones during heatwaves, that is, spells of extreme air temperature (>37°C for ≥2 consecutive days) which hit the study area during the nestling-rearing phase in both years. Hatching failure markedly increased with increasing nest temperature, rising above 50% when maximum nest temperatures exceeded 44°C. Nestlings from control nest boxes showed higher mortality during heatwaves (55% vs. 10% in shaded nest boxes) and those that survived further showed impaired morphological growth (body mass and skeletal size). Hence, heatwaves occurring during the breeding period can have both strong lethal and sublethal impacts on different components of avian reproduction, from egg hatching to nestling growth. More broadly, these findings suggest that the projected future increases of summer temperatures and heatwave frequency in the Mediterranean basin and elsewhere in temperate areas may threaten the local persistence of even relatively warm-adapted species.

Mapping suitable habitats for globally endangered raptors in Kenya: Integrating climate factors and conservation planning

Raptors face global threats like electrocution, collisions, and habitat fragmentation. Many species remain understudied, and their distribution patterns are unknown. Understanding their current and future distribution is crucial for conservation. Protecting these top predators requires knowledge of their spatial distribution and environmental influences. This study addresses knowledge gaps in raptor habitats and distributions in Kenya, considering current and future climate changes. Using species distribution models and occurrence data from the Global Biodiversity Information Facility, we evaluated suitable habitats for four endangered Kenyan raptor species: Martial eagle, Secretarybird, Bateleur, and Steppe Eagle. We assessed the impact of climatic predictors on their distribution, considering two climate change scenarios for 2020-2040. Our findings reveal that raptor distribution in Kenya is predominantly concentrated in the southwestern region, extending into the central region of the country. The most significant predictors of raptor species distribution varied for each species, with Steppe eagle and Secretarybird being highly influenced by precipitation during the warmest quarter, Martial eagle being influenced by mean temperature during the driest quarter, and Bateleur being primarily influenced by precipitation during the coldest quarter. When projecting our model into the climate change scenarios for 2020-2040, all species except the Bateleur exhibited a negative range shift. The results of our study suggest that climate change may have adverse impacts on the raptor species examined. In light of these findings, we recommend implementing targeted monitoring and conducting surveys in accordance with our current model predictions. Specifically, our focus should be on monitoring areas that exhibit the highest climate suitability, as these areas are likely to undergo significant shifts in the near future. By conducting regular monitoring and engaging in further research, we can enhance our understanding of these raptor species and gather valuable data to improve the accuracy and reliability of our model predictions.

Time to Step Up Conservation: Climate Change Will Further Reduce the Suitable Habitats for the Vulnerable Species Marbled Polecat (Vormela peregusna)

Habitat loss and human threats are putting the marbled polecat (Vormela peregusna) on the brink of extinction. Numerous recent studies have found that climate change will further deteriorate the living environment of endangered species, leading to their eventual extinction. In this study, we used the results of infrared camera surveys in China and worldwide distribution data to construct an ensemble model consisting of 10 commonly used ecological niche models to specify potential suitable habitat areas for V. peregusna under current conditions with similar environments to the sighting record sites. Changes in the suitable habitat for V. peregusna under future climate change scenarios were simulated using mid-century (2050s) and the end of the century (2090s) climate scenarios provided by the Coupled Model Intercomparison Project Phase 6 (CMIP6). We evaluated the accuracy of the model to obtain the environmental probability values (cutoff) of the V. peregusna distribution, the current distribution of suitable habitats, and future changes in moderately and highly suitable habitat areas. The results showed that the general linear model (GLM) was the best single model for predicting suitable habitats for V. peregusna, and the kappa coefficient, area under the curve (AUC), and true skill statistic (TSS) of the ensemble model all exceeded 0.9, reflecting greater accuracy and stability than single models. Under the current conditions, the area of suitable habitat for V. peregusna reached 3935.92 × 10⁴ km², suggesting a wide distribution range. In the future, climate change is predicted to severely affect the distribution of V. peregusna and substantially reduce the area of suitable habitats for the species, with 11.91 to 33.55% of moderately and highly suitable habitat areas no longer suitable for the survival of V. peregusna. This shift poses an extremely serious challenge to the conservation of this species. We suggest that attention be given to this problem in Europe, especially the countries surrounding the Black Sea, Asia, China, and Mongolia, and that measures be taken, such as regular monitoring and designating protected areas for the conservation of vulnerable animals.

Interactive effects of rising temperatures and urbanisation on birds across different climate zones: A mechanistic perspective

Climate change and urbanisation are among the most pervasive and rapidly growing threats to biodiversity worldwide. However, their impacts are usually considered in isolation, and interactions are rarely examined. Predicting species' responses to the combined effects of climate change and urbanisation, therefore, represents a pressing challenge in global change biology. Birds are important model taxa for exploring the impacts of both climate change and urbanisation, and their behaviour and physiology have been well studied in urban and non-urban systems. This understanding should allow interactive effects of rising temperatures and urbanisation to be inferred, yet considerations of these interactions are almost entirely lacking from empirical research. Here, we synthesise our current understanding of the potential mechanisms that could affect how species respond to the combined effects of rising temperatures and urbanisation, with a focus on avian taxa. We discuss potential interactive effects to motivate future in-depth research on this critically important, yet overlooked, aspect of global change biology. Increased temperatures are a pronounced consequence of both urbanisation (through the urban heat island effect) and climate change. The biological impact of this warming in urban and non-urban systems will likely differ in magnitude and direction when interacting with other factors that typically vary between these habitats, such as resource availability (e.g. water, food and microsites) and pollution levels. Furthermore, the nature of such interactions may differ for cities situated in different climate types, for example, tropical, arid, temperate, continental and polar. Within this article, we highlight the potential for interactive effects of climate and urban drivers on the mechanistic responses of birds, identify knowledge gaps and propose promising future research avenues. A deeper understanding of the behavioural and physiological mechanisms mediating species' responses to urbanisation and rising temperatures will provide novel insights into ecology and evolution under global change and may help better predict future population responses.

Short- and long-term consequences of heat exposure on mitochondrial metabolism in zebra finches (Taeniopygia castanotis)

Understanding the consequences of heat exposure on mitochondrial function is crucial as mitochondria lie at the core of metabolic processes, also affecting population dynamics. In adults, mitochondrial metabolism varies with temperature but can also depend on thermal conditions experienced during development. We exposed zebra finches to two alternative heat treatments during early development: "constant", maintained birds at ambient 35 °C from parental pair formation to fledglings' independence, while "periodic" heated broods at 40 °C, 6 h daily at nestling stage. Two years later, we acclimated birds from both experiments at 25 °C for 21 days, before exposing them to artificial heat (40 °C, 5 h daily for 10 days). After both conditions, we measured red blood cells' mitochondrial metabolism using a high-resolution respirometer. We found significantly decreased mitochondrial metabolism for Routine, Oxidative Phosphorylation (OxPhos) and Electron Transport System maximum capacity (ETS) after the heat treatments. In addition, the birds exposed to "constant" heat in early life showed lower oxygen consumption at the Proton Leak (Leak) stage after the heat treatment as adults. Females showed higher mitochondrial respiration for Routine, ETS and Leak independent of the treatments, while this pattern was reversed for OxPhos coupling efficiency (OxCE). Our results show that short-term acclimation involved reduced mitochondrial respiration, and that the reaction of adult birds to heat depends on the intensity, pattern and duration of temperature conditions experienced at early-life stages. Our study provides insight into the complexity underlying variation in mitochondrial metabolism and raises questions on the adaptive value of long-lasting physiological adjustments triggered by the early-life thermal environment.

Concordant and opposing effects of climate and land-use change on avian assemblages in California's most transformed landscapes

Climate and land-use change could exhibit concordant effects that favor or disfavor the same species, which would amplify their impacts, or species may respond to each threat in a divergent manner, causing opposing effects that moderate their impacts in isolation. We used early 20th century surveys of birds conducted by Joseph Grinnell paired with modern resurveys and land-use change reconstructed from historic maps to examine avian change in Los Angeles and California's Central Valley (and their surrounding foothills). Occupancy and species richness declined greatly in Los Angeles from urbanization, strong warming (+1.8°C), and drying (-77.2 millimeters) but remained stable in the Central Valley, despite large-scale agricultural development, average warming (+0.9°C), and increased precipitation (+11.2 millimeters). While climate was the main driver of species distributions a century ago, the combined impacts of land-use and climate change drove temporal changes in occupancy, with similar numbers of species experiencing concordant and opposing effects.

Consequences of arthropod community structure for an at-risk insectivorous bird

Global declines in bird and arthropod abundance highlights the importance of understanding the role of food limitation and arthropod community composition for the performance of insectivorous birds. In this study, we link data on nestling diet, arthropod availability and nesting performance for the Coastal Cactus Wren (Campylorhynchus brunneicapillus sandiegensis), an at-risk insectivorous bird native to coastal southern California and Baja Mexico. We used DNA metabarcoding to characterize nestling diets and monitored 8 bird territories over two years to assess the relationship between arthropod and vegetation community composition and bird reproductive success. We document a discordance between consumed prey and arthropod biomass within nesting territories, in which Diptera and Lepidoptera were the most frequently consumed prey taxa but were relatively rare in the environment. In contrast other Orders (e.g., Hemiptera, Hymenoptera)were abundant in the environment but were absent from nestling diets. Accordingly, variation in bird reproductive success among territories was positively related to the relative abundance of Lepidoptera (but not Diptera), which were most abundant on 2 shrub species (Eriogonum fasciculatum, Sambucus nigra) of the 9 habitat elements characterized (8 dominant plant species and bare ground). Bird reproductive success was in turn negatively related to two invasive arthropods whose abundance was not associated with preferred bird prey, but instead possibly acted through harassment (Linepithema humile; Argentine ants) and parasite transmission or low nutritional quality (Armadillidium vulgare; "pill-bug"). These results demonstrate how multiple aspects of arthropod community structure can influence bird performance through complementary mechanisms, and the importance of managing for arthropods in bird conservation efforts.

Climate Change and Wetlands in the Southern Great Plains: How Are Managers Dealing with an Uncertain Future?

Little guidance is available to assist wetland managers in developing climate adaptation plans. To facilitate development of recommendations for adaptation strategies, it is essential to first determine if or how wetland managers are addressing these challenges. We used an online survey to solicit feedback from wetland managers and biologists in the Southern Great Plains of North America to gain information on perceptions of wetland managers regarding climate change; assess how the effects of climate change are being addressed through management; and identify barriers to implementing climate change adaptation. The majority of wetland managers (63%) agreed they are currently experiencing effects of climate change in wetlands, and most respondents (76%) reported that changes in the timing of water availability throughout the year was the most likely impact. Managers reported using a diversity of approaches in managing for changing precipitation, with management of native and invasive plant species being the two most common practices. Lack of funding and personnel were the most commonly identified factors limiting manager's response to changing precipitation patterns. In addition, >50% of managers indicated uncertainty about the effects of climate change on wetlands as a barrier to management, which may relate to limited access to peer-reviewed science. While most of the management practices reported were short-term measures and may not reflect long-term adaptation for climate change, the fact that many managers are considering climate change in their management suggests that there is considerable opportunities to continue developing capacity for climate change adaptation in the region.

Biased assessment of thermal properties of birds from estimated body density

Parameter approximation is often necessary when calculating species thermal properties, and researchers historically have assumed animals are spherical when estimating volume and density. We hypothesized that a spherical model would result in significantly biased measures of density for birds, which are generally longer than they are tall or wide, and that these inaccuracies would significantly alter the outputs of thermal models. We calculated the densities of 154 bird species using sphere and ellipsoid volume equations and compared these estimates to one another and to published bird densities measured using more exact volume displacement methods. We also calculated evaporative water loss as a percentage of body mass per hour, a variable known to be critical for bird survival, twice for each species, once with the sphere-based density and once with the ellipsoid-based density. We found that volume and density estimates were statistically similar between published densities and those estimated using the ellipsoid volume equation, suggesting that this method is suitable for approximating bird volume and calculating density. In contrast, the spherical model overestimated body volume and therefore underestimated body densities. This resulted in the spherical approach consistently overestimating evaporative water loss as a percent of mass lost per hour than the ellipsoid approach. This outcome would result in mischaracterizing thermal conditions as lethal for a given species, including overestimating vulnerability to increased temperatures due to climate change.

Challenges and solutions to biodiversity conservation in arid lands

The strategic goals of the United Nations and the Aichi Targets for biodiversity conservation have not been met. Instead, biodiversity has continued to rapidly decrease, especially in developing countries. Setting a new global biodiversity framework requires clarifying future priorities and strategies to bridge challenges and provide representative solutions. Hyper-arid, arid, and semi-arid lands (herein, arid lands) form about one third of the Earth's terrestrial surface. Arid lands contain unique biological and cultural diversity, and biodiversity loss in arid lands can have a disproportionate impact on these ecosystems due to low redundancy and a high risk of trophic cascades. They contain unique biological and cultural diversity and host many endemic species, including wild relatives of key crop plants. Yet extensive agriculture, unsustainable use, and global climate change are causing an irrecoverable damage to arid lands, with far-reaching consequences to the species, ground-water resources, ecosystem productivity, and ultimately the communities' dependant on these systems. However, adequate research and effective policies to protect arid land biodiversity and sustainability are lacking because a large proportion of arid areas are in developing countries, and the unique diversity in these systems is frequently overlooked. Developing new priorities for global arid lands and mechanisms to prevent unsustainable development must become part of public discourse and form the basis for conservation efforts. The current situation demands the combined efforts of researchers, practitioners, policymakers, and local communities to adopt a socio-ecological approach for achieving sustainable development (SDGs) in arid lands. Applying these initiatives globally is imperative to conserve arid lands biodiversity and the critical ecological services they provide for future generations. This perspective provides a framework for conserving biodiversity in arid lands for all stakeholders that will have a tangible impact on sustainable development, nature, and human well-being.

Global patterns of climate change impacts on desert bird communities

The world's warm deserts are predicted to experience disproportionately large temperature increases due to climate change, yet the impacts on global desert biodiversity remain poorly understood. Because species in warm deserts live close to their physiological limits, additional warming may induce local extinctions. Here, we combine climate change projections with biophysical models and species distributions to predict physiological impacts of climate change on desert birds globally. Our results show heterogeneous impacts between and within warm deserts. Moreover, spatial patterns of physiological impacts do not simply mirror air temperature changes. Climate change refugia, defined as warm desert areas with high avian diversity and low predicted physiological impacts, are predicted to persist in varying extents in different desert realms. Only a small proportion (<20%) of refugia fall within existing protected areas. Our analysis highlights the need to increase protection of refugial areas within the world's warm deserts to protect species from climate change.

Climate Change and Dispersal Ability Jointly Affects the Future Distribution of Crocodile Lizards

Crocodile lizards (Shinisaurus crocodilurus) are an endangered, 'living fossil' reptile from a monophyletic family and therefore, a high priority for conservation. We constructed climatic models to evaluate the potential impact of climate change on the distribution of crocodile lizards for the period 2000 to 2100 and determined the key environmental factors that affect the dispersal of this endangered species. For the construction of climatic models, we used 985 presence-only data points and 6 predictor variables which showed excellent performance (AUC = 0.974). The three top-ranked factors predicting crocodile lizard distribution were precipitation of the wettest month (bio13, 37.1%), precipitation of the coldest quarter (bio19, 17.9%), and temperature seasonality (bio4, 14.3%). Crocodile lizards were, just as they are now, widely distributed in the north of Guangdong Province in China and Quảng Ninh Province in Vietnam at the last glacial maximum (LGM). Since the LGM, there has been an increase in suitable habitats, particularly in east-central Guangxi Province, China. Under future global warming scenarios, the potential habitat for crocodile lizards is expected to decrease significantly in the next 100 years. Under the most optimistic scenario, only 7.35% to 6.54% of suitable habitat will remain, and under the worst climatic scenario, only 8.34% to 0.86% of suitable habitat will remain. Models for no dispersal and limited dispersal showed that all crocodile lizards would lose habitat as temperatures increase. Our work contributes to an increased understanding of the current and future spatial distribution of the species, supporting practical management and conservation plans.

Environmental conditions lead to shifts in individual communication, which can cause cascading effects on soundscape composition

Climate change is increasing aridity in grassland and desert habitats across the southwestern United States, reducing available resources and drastically changing the breeding habitat of many bird species. Increases in aridity reduce sound propagation distances, potentially impacting habitat soundscapes, and could lead to a breakdown of the avian soundscapes in the form of loss of vocal culture, reduced mating opportunities, and local population extinctions. We developed an agent-based model to examine how changes in aridity will affect both sound propagation and the ability of territorial birds to audibly contact their neighbors. We simulated vocal signal attenuation under a variety of environmental scenarios for the south, central semi-arid prairies of the United States, ranging from contemporary weather conditions to predicted droughts under climate change. We also simulated how changes in physiological conditions, mainly evaporative water loss (EWL), would affect singing behavior. Under contemporary and climate change-induced drought conditions, we found that significantly fewer individuals successfully contacted all adjacent neighbors than did individuals in either the contemporary or predicted climate change conditions. We also found that at higher sound frequencies and higher EWL, fewer individuals were able to successfully contact all their neighbors, particularly in drought and climate change drought conditions. These results indicate that climate change-mediated aridification may alter the avian soundscape, such that vocal communication no longer effectively functions for mate attraction or territorial defense. As climate change progresses, increased aridity in current grasslands may favor shifts toward low-frequency songs, colonial resource use, and altered songbird community compositions.

Long-term changes in avian biomass and functional diversity within disturbed and undisturbed Amazonian rainforest

Recent long-term studies in protected areas have revealed the loss of biodiversity, yet the ramifications for ecosystem health and resilience remain unknown. Here, we investigate how the loss of understory birds, in the lowest stratum of the forest, affects avian biomass and functional diversity in the Amazon rainforest. Across approximately 30 years in the Biological Dynamics of Forest Fragments Project, we used a historical baseline of avian communities to contrast the avian communities in today's primary forest with those in modern disturbed habitat. We found that in primary rainforest, the reduced abundance of insectivorous species led to reduced functional diversity, but no reduction of biomass, indicating that species with similar functional traits are less likely to coexist in modern primary forests. Because today's forests contain fewer functionally redundant species-those with similar traits-we argue that avian communities in modern primary Amazonian rainforests are less resilient, which may ultimately disrupt the ecosystem in dynamic and unforeseen ways.

Was Henry David Thoreau a Good Naturalist? An Approach for Assessing Data from Historical Natural History Records

Ecologists are increasingly combining historical observations made by naturalists with modern observations to detect the ecological effects of climate change. This use of historical observations raises the following question: How do we know that historical data are appropriate to use to answer current ecological questions? In the present article, we address this question for environmental philosopher Henry David Thoreau, author of Walden. Should we trust his observations? We qualitatively and quantitatively evaluate Thoreau's observations using a three-step framework: We assess the rigor, accuracy, and utility of his observations to investigate changes in plants and animals over time. We conclude that Thoreau was an accurate observer of nature and a reliable scientist. More importantly, we describe how this simple three-step approach could be used to assess the accuracy of other scientists and naturalists.

Host species and environment drivers of ectoparasite community of rodents in a Mojave Desert wetlands

Drivers of patterns of ectoparasitism in rodents in patchy Mojave Desert wetlands were investigated. A total of 1,571 ectoparasites in Mesostigmata, Trombidiformes, Siphonaptera and Ixodida were collected from 341 rodents (Microtus californicus scirpensis, Mus musculus, Reithrodontomys megalotis, Peromyscus eremicus, and Neotoma lepida) at eleven marshes. Trombiculids accounted for 82.5% of mites, followed by the mesostigmatid Ornithonyssus bacoti (17.5%), with chiggers predominating on voles and harvest mice. There were at least three genera of chiggers (Eutrombicula alfreddugesi, Euschoengastia sp. novel, and Blankaartia sp. novel). Fleas included Orchopeas leucopus (90.3% of all fleas) and O. sexdentatus (9.7%), and ticks were the novel endemic Ixodes mojavensis (82.1% of ticks) and Dermacentor similis (17.9%). On all hosts and at all marshes, coverage-based rarefaction sampling was over 96%, indicating coverage sufficient for analysis. Dissimilarities in ectoparasite community structure were driven mainly by chiggers, I. mojavensis and O. leucopus. Northern marshes were dominated by chiggers; central marshes by I. mojavensis; and southern marshes by O. leucopus. Primary determinants of ectoparasite community structure were host species, patch size, and parasite interspecific interactions. Host species richness and environmental factors such as patch distance and water and plant availability were not significantly associated with patterns of ectoparasitism. There were nine (60%) significant negative pairwise associations between ectoparasite taxa and no significant positive relationships. Ixodes mojavensis had the highest number of negative associations (with five other species), followed by chiggers and O. bacoti with two negative associations each. The study area is among the most arid in North America and supports numerous rare and endemic species in increasingly isolated wetland habitat patches; knowledge of ectoparasite ecology in this region identifies potential ectoparasite vectors, and provides information needed to design and implement programs to manage vector-borne diseases for purposes of wildlife conservation.

Collapse of Breeding Success in Desert-Dwelling Hornbills Evident Within a Single Decade

Rapid anthropogenic climate change potentially severely reduces avian breeding success. While the consequences of high temperatures and drought are reasonably well-studied within single breeding seasons, their impacts over decadal time scales are less clear. We assessed the effects of air temperature (Tair) and drought on the breeding output of southern yellow-billed hornbills (Tockus leucomelas; hornbills) in the Kalahari Desert over a decade (2008–2019). We aimed to document trends in breeding performance in an arid-zone bird during a time of rapid global warming and identify potential drivers of variation in breeding performance. The breeding output of our study population collapsed during the monitoring period. Comparing the first three seasons (2008–2011) of monitoring to the last three seasons (2016–2019), the mean percentage of nest boxes that were occupied declined from 52% to 12%, nest success from 58% to 17%, and mean fledglings produced per breeding attempt from 1.1 to 0.4. Breeding output was negatively correlated with increasing days on which Tmax (mean maximum daily Tair) exceeded the threshold Tair at which male hornbills show a 50% likelihood of engaging in heat dissipation behavior [i.e., panting (Tthresh; Tair = 34.5°C)] and the occurrence of drought within the breeding season, as well as later dates for entry into the nest cavity (i.e., nest initiation) and fewer days post-hatch, spent incarcerated in the nest by the female parent. The apparent effects of high Tair were present even in non-drought years; of the 115 breeding attempts that were recorded, all 18 attempts that had ≥ 72% days during the attempt on which Tmax &gt; Tthresh failed (equivalent to Tmax during the attempt ≥ 35.7°C). This suggests that global warming was likely the primary driver of the recent, rapid breeding success collapse. Based on current warming trends, the Tmax threshold of 35.7°C, above which no successful breeding attempts were recorded, will be exceeded during the entire hornbill breeding season by approximately 2027 at our study site. Therefore, our findings support the prediction that climate change may drive rapid declines and cause local extinctions despite the absence of direct lethal effects of extreme heat events.

Vulnerability of avian populations to renewable energy production

Renewable energy production can kill individual birds, but little is known about how it affects avian populations. We assessed the vulnerability of populations for 23 priority bird species killed at wind and solar facilities in California, USA. Bayesian hierarchical models suggested that 48% of these species were vulnerable to population-level effects from added fatalities caused by renewables and other sources. Effects of renewables extended far beyond the location of energy production to impact bird populations in distant regions across continental migration networks. Populations of species associated with grasslands where turbines were located were most vulnerable to wind. Populations of nocturnal migrant species were most vulnerable to solar, despite not typically being associated with deserts where the solar facilities we evaluated were located. Our findings indicate that addressing declines of North American bird populations requires consideration of the effects of renewables and other anthropogenic threats on both nearby and distant populations of vulnerable species.

Combined climatic and anthropogenic stress threaten resilience of important wetland sites in an arid region

Climate change and anthropogenic perturbation threaten resilience of wetlands globally, particularly in regions where environmental conditions are already hot and dry, and human impacts are rapidly intensifying and expanding. Here we assess the vulnerability of Ramsar wetlands of six North African countries (Western Sahara, Morocco, Algeria, Tunisia, Libya, and Egypt) by asking three questions: (1) what are the recent anthropogenic changes that the wetlands experienced? (2) what are the projected future climatic changes? (3) how wetlands with different conservation priorities and globally threatened species are impacted by anthropogenic pressures? We used climatic data (historical and future projections) from WorldClim 2, drought index (SPEI), and human footprint index (HFI for 2000 and 2019) to estimate anthropogenic pressures, as well as waterbird conservation value (WCV: a metric indicating conservation priority of sites) and the breeding distribution of three threatened waterbird species (Aythya nyroca, Marmaronetta angustirostris, and Oxyura leucocephala) to understand how biodiversity is impacted by anthropogenic pressure. We found that temperature, precipitation, drought, and human footprint index (HFI) increased during earlier decades. Interestingly, areas with high HFI are projected to encounter lower warming but more severe drought. We also found that WCV was positively correlated with the magnitude of current HFI, indicating that sites of high conservation value for waterbirds encounter higher levels of anthropogenic pressure. The breeding range of the three threatened species of waterbirds showed a marked increase in HFI and is projected to experience a severe increase in temperature by 2081-2100, especially under the high emission scenario (SSP8.5) where environmental temperature becomes closer to the species critical maximum. Our results highlight the importance of integrating new conservation measures that increase the resilience of North African protected wetlands to reduce extinction risk to biodiversity.

Automatic variable selection in ecological niche modeling: A case study using Cassin's Sparrow (Peucaea cassinii)

MERRA/Max provides a feature selection approach to dimensionality reduction that enables direct use of global climate model outputs in ecological niche modeling. The system accomplishes this reduction through a Monte Carlo optimization in which many independent MaxEnt runs, operating on a species occurrence file and a small set of randomly selected variables in a large collection of variables, converge on an estimate of the top contributing predictors in the larger collection. These top predictors can be viewed as potential candidates in the variable selection step of the ecological niche modeling process. MERRA/Max's Monte Carlo algorithm operates on files stored in the underlying filesystem, making it scalable to large data sets. Its software components can run as parallel processes in a high-performance cloud computing environment to yield near real-time performance. In tests using Cassin's Sparrow (Peucaea cassinii) as the target species, MERRA/Max selected a set of predictors from Worldclim's Bioclim collection of 19 environmental variables that have been shown to be important determinants of the species' bioclimatic niche. It also selected biologically and ecologically plausible predictors from a more diverse set of 86 environmental variables derived from NASA's Modern-Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2) reanalysis, an output product of the Goddard Earth Observing System Version 5 (GEOS-5) modeling system. We believe these results point to a technological approach that could expand the use global climate model outputs in ecological niche modeling, foster exploratory experimentation with otherwise difficult-to-use climate data sets, streamline the modeling process, and, eventually, enable automated bioclimatic modeling as a practical, readily accessible, low-cost, commercial cloud service.

RAD Adaptive Management for Transforming Ecosystems

Intensifying global change is propelling many ecosystems toward irreversible transformations. Natural resource managers face the complex task of conserving these important resources under unprecedented conditions and expanding uncertainty. As once familiar ecological conditions disappear, traditional management approaches that assume the future will reflect the past are becoming increasingly untenable. In the present article, we place adaptive management within the resist–accept–direct (RAD) framework to assist informed risk taking for transforming ecosystems. This approach empowers managers to use familiar techniques associated with adaptive management in the unfamiliar territory of ecosystem transformation. By providing a common lexicon, it gives decision makers agency to revisit objectives, consider new system trajectories, and discuss RAD strategies in relation to current system state and direction of change. Operationalizing RAD adaptive management requires periodic review and update of management actions and objectives; monitoring, experimentation, and pilot studies; and bet hedging to better identify and tolerate associated risks.

Disentangling climatic and nest predator impact on reproductive output reveals adverse high-temperature effects regardless of helper number in an arid-region cooperative bird

Climate exerts a major influence on reproductive processes, and an understanding of the mechanisms involved and which factors might mitigate adverse weather is fundamental under the ongoing climate change. Here, we study how weather and nest predation influence reproductive output in a social species, and examine whether larger group sizes can mitigate the adverse effects of these factors. We used a 7‐year nest predator‐exclusion experiment on an arid‐region cooperatively breeding bird, the sociable weaver. We found that dry and, especially, hot weather were major drivers of nestling mortality through their influence on nest predation. However, when we experimentally excluded nest predators, these conditions were still strongly associated with nestling mortality. Group size was unimportant against nest predation and, although positively associated with reproductive success, it did not mitigate the effects of adverse weather. Hence, cooperative breeding might have a limited capacity to mitigate extreme weather effects.

Integrative Physiological Responses to Acute Dehydration in the Rufous-Collared Sparrow: Metabolic, Enzymatic, and Oxidative Traits

Predictions indicate that birds worldwide will be affected by global warming and extreme climatic events which is especially relevant for passerines because the diurnal habits, small body size, and high mass-adjusted metabolic rates of this group make it particularly susceptible to increases in temperature and aridity. Some bird species respond to conditions that stress osmoregulation by increasing their rates of energy expenditure, nevertheless, the effect of dehydration on metabolic rates in birds has produced contrasting results. It also remains unknown whether hydration state may cause shifts in tissue-specific metabolic rates or modify tissue oxidative status. We used the rufous-collared sparrow (Zonotrichia capensis), to experimentally test the effect of dehydration on metabolic enzymes in erythrocytes, tissue oxidative status, basal metabolic rate (BMR), and total evaporative water loss. We found a significant increase in mass-adjusted BMR in water restricted (WR) birds compared to control birds (CT). Activity of cytochrome-c-oxidase (COX) in red blood cells (RBCs) was also significantly higher in the WR group relative to the CT group and this activity was positively correlated with mass-adjusted BMR. We found a moderate effect of water restriction on membrane damage of skeletal muscle. In a second set of individuals subjected to the same experimental conditions, lean mass and total water were tightly correlated and decreased by 10 and 12%, respectively, in birds in the WR group relative to the CT group. Decreases in total water and lean mass leads to an increase in mass-adjusted BMR in WR Z. capensis, suggesting that birds may simultaneously increase protein catabolism and production of metabolic water through oxidation. The significant positive relationship between BMR and COX in RBCs is a finding that requires additional research to determine whether erythrocyte metabolism is affected by dehydration per se and or it more generally reflects rates of energy expenditure in birds.

Climate change effects on desert ecosystems: A case study on the keystone species of the Namib Desert Welwitschia mirabilis

Deserts have been predicted to be one of the most responsive ecosystems to global climate change. In this study, we examine the spatial and demographic response of a keystone endemic plant of the Namib Desert (Welwitschia mirabilis), for which displacement and reduction of suitable climate has been foreseen under future conditions. The main aim is to assess the association between ongoing climate change and geographical patterns of welwitschia health, reproductive status, and size. We collected data on welwitschia distribution, health condition, reproductive status, and plant size in northern Namibia. We used ecological niche models to predict the expected geographic shift of suitability under climate change scenarios. For each variable, we compared our field measurements with the expected ongoing change in climate suitability. Finally, we tested the presence of simple geographical gradients in the observed patterns. The historically realized thermal niche of welwitschia will be almost completely unavailable in the next 30 years in northern Namibia. Expected reductions of climatic suitability in our study sites were strongly associated with indicators of negative population conditions, namely lower plant health, reduced recruitment and increased adult mortality. Population condition does not follow simple latitudinal or altitudinal gradients. The observed pattern of population traits is consistent with climate change trends and projections. This makes welwitschia a suitable bioindicator (i.e. a 'sentinel') for climate change effect in the Namib Desert ecosystems. Our spatially explicit approach, combining suitability modeling with geographic combinations of population conditions measured in the field, could be extensively adopted to identify sentinel species, and detect population responses to climate change in other regions and ecosystems.

Desert Related Death

Introduction: Desert death is defined as any death that occurs in the desert and could be attributed to a list of causes including environmental, animal related, undetermined, and other causes. Death in the desert seems to be obscure and little discussed in the field of forensic medicine, despite its importance, and there is only limited literature available on this broad topic. This narrative review aims to identify the most common causes of desert death and its medicolegal implications. Desert death causes: Environmental causes of death could be a result of temperature and lightening-related causes. Moreover, a variety of animals found in deserts are considered to be threatening and fatal, in addition to other and undetermined causes. Medicolegal implications of desert death: Likely to arise from the difficulties faced in finding the cause of death are the identification of the victim and the postmortem injuries that occur. Conclusion: Desert death is a broad topic with great medicolegal significance. More information and case reports need to be added in the literature. Guidelines for people about the danger of going to deserts in specific weather conditions should be implemented. Safety regulations must be taken into account at all times.

Factors influencing distributional shifts and abundance at the range core of a climate-sensitive mammal

Species are frequently responding to contemporary climate change by shifting to higher elevations and poleward to track suitable climate space. However, depending on local conditions and species' sensitivity, the nature of these shifts can be highly variable and difficult to predict. Here, we examine how the American pika (Ochotona princeps), a philopatric, montane lagomorph, responds to climatic gradients at three spatial scales. Using mixed-effects modeling in an information-theoretic approach, we evaluated a priori model suites regarding predictors of site occupancy, relative abundance, and elevational-range retraction across 760 talus patches, nested within 64 watersheds across the Northern Rocky Mountains of North America, during 2017-2020. The top environmental predictors differed across these response metrics. Warmer temperatures in summer and winter were associated with lower occupancy, lower relative abundances, and greater elevational retraction across watersheds. Occupancy was also strongly influenced by habitat patch size, but only when combined with climate metrics such as actual evapotranspiration. Using a second analytical approach, acute heat stress and summer precipitation best explained retraction residuals (i.e., the relative extent of retraction given the original elevational range of occupancy). Despite the study domain occurring near the species' geographic-range center, where populations might have higher abundances and be at lower risk of climate-related stress, 33.9% of patches showed evidence of recent extirpations. Pika-extirpated sites averaged 1.44℃ warmer in summer than did occupied sites. Additionally, the minimum elevation of pika occupancy has retracted upslope in 69% of watersheds (mean: 281 m). Our results emphasize the nuance associated with evaluating species' range dynamics in response to climate gradients, variability, and temperature exceedances, especially in regions where species occupy gradients of conditions that may constitute multiple range edges. Furthermore, this study highlights the importance of evaluating diverse drivers across response metrics to improve the predictive accuracy of widely used, correlative models.

Triple Oxygen Isotope Measurements (Δ'17O) of Body Water Reflect Water Intake, Metabolism, and δ18O of Ingested Water in Passerines

Understanding physiological traits and ecological conditions that influence a species reliance on metabolic water is critical to creating accurate physiological models that can assess their ability to adapt to environmental perturbations (e.g., drought) that impact water availability. However, relatively few studies have examined variation in the sources of water animals use to maintain water balance, and even fewer have focused on the role of metabolic water. A key reason is methodological limitations. Here, we applied a new method that measures the triple oxygen isotopic composition of a single blood sample to estimate the contribution of metabolic water to the body water pool of three passerine species. This approach relies on Δ'¹⁷O, defined as the residual from the tight linear correlation that naturally exists between δ¹⁷O and δ¹⁸O values. Importantly, Δ'17O is relatively insensitive to key fractionation processes, such as Rayleigh distillation in the water cycle that have hindered previous isotope-based assessments of animal water balance. We evaluated the effects of changes in metabolic rate and water intake on Δ'¹⁷O values of captive rufous-collared sparrows (Zonotrichia capensis) and two invertivorous passerine species in the genus Cinclodes from the field. As predicted, colder acclimation temperatures induced increases in metabolic rate, decreases in water intake, and increases in the contribution of metabolic water to the body water pool of Z. capensis, causing a consistent change in Δ'¹⁷O. Measurement of Δ'¹⁷O also provides an estimate of the δ¹⁸O composition of ingested pre-formed (drinking/food) water. Estimated δ¹⁸O values of drinking/food water for captive Z. capensis were ~ −11‰, which is consistent with that of tap water in Santiago, Chile. In contrast, δ¹⁸O values of drinking/food water ingested by wild-caught Cinclodes were similar to that of seawater, which is consistent with their reliance on marine resources. Our results confirm the utility of this method for quantifying the relative contribution of metabolic versus pre-formed drinking/food water to the body water pool in birds.

Landscape Attributes Best Explain the Population Trend of Wintering Greater White-Fronted Goose (Anser albifrons) in the Yangtze River Floodplain

Biodiversity in the Middle and Lower Yangtze Floodplain has critically decreased during the last several decades, driven by numerous determinants. Hence, identification of primary drivers of animal population decline is a priority for conservation. Analyzing long time-series data is a powerful way to assess drivers of declines, but the data are often missing, hampering effective conservation policymaking. In this study, based on twenty-four years (from 1996 to 2019) of annual maximal count data, we investigated the effects of climate and landscape changes on the increasing population trend of the Greater White-Fronted Goose (Anser albifrons) at a Ramsar site in the Middle and Lower Yangtze Floodplain, China. Our results showed that the availability of a suitable habitat and landscape attributes are the key driving forces affecting the population trend, while the effects of climate factors are weak. Specifically, increasing the area of suitable habitat and alleviating habitat fragmentation through a fishing ban policy may have provided a more suitable habitat to the geese, contributing to the increasing population trend. However, we also observed that the grazing prohibition policy implemented in 2017 at Shengjin Lake may have potentially negatively affected geese abundance, as grazing by larger herbivores may favor smaller geese species by modifying the vegetation community and structure. Based on our results, we suggest several practical countermeasures to improve the habitat suitability for herbivorous goose species wintering in this region.

Community Bioacoustics: Studying Acoustic Community Structure for Ecological and Conservation Insights

The diversity of animal acoustic signals has evolved due to multiple ecological processes, both biotic and abiotic. At the level of communities of signaling animals, these processes may lead to diverse outcomes, including partitioning of acoustic signals along multiple axes (divergent signal parameters, signaling locations, and timing). Acoustic data provides information on the organization, diversity and dynamics of an acoustic community, and thus enables study of ecological change and turnover in a non-intrusive way. In this review, we lay out how community bioacoustics (the study of acoustic community structure and dynamics), has value in ecological monitoring and conservation of diverse landscapes and taxa. First, we review the concepts of signal space, signal partitioning and their effects on the structure of acoustic communities. Next, we highlight how spatiotemporal ecological change is reflected in acoustic community structure, and the potential this presents in monitoring and conservation. As passive acoustic monitoring gains popularity worldwide, we propose that the analytical framework of community bioacoustics has promise in studying the response of entire suites of species (from insects to large whales) to rapid anthropogenic change.

Direct and indirect effects of high temperatures on fledging in a cooperatively breeding bird

High temperatures and low rainfall consistently constrain reproduction in arid-zone bird species. Understanding the mechanisms underlying this pattern is critical for predicting how climate change will influence population persistence and to inform conservation and management. In this study, we analyzed Southern Pied Babbler Turdoides bicolor nestling survival, daily growth rate and adult investment behavior during the nestling period over three austral summer breeding seasons. High temperatures were associated with lower body mass, shorter tarsi, and reduced daily growth rates of nestlings. Our piecewise structural equation models suggested that direct impacts of temperature had the strongest influence on nestling size and daily growth rates for both 5-day-old and 11-day-old nestlings, followed by temperature-related adjustments to provisioning rates by adults. Rainfall and group size influenced the behavior of provisioning adults but did not influence nestling growth or survival. Adjustments to adult provisioning strategies did not compensate for direct negative effects of high air temperatures on nestling size or daily growth rates. Detailed mechanistic data like these allow us to model the pathways by which high temperature causes nest failure. In turn, this could allow us to design targeted conservation action to effectively mitigate climate effects.

Migration dynamics of polar bears (Ursus maritimus) in western Hudson Bay

Migration is predicted to change both spatially and temporally as climate change alters seasonal resource availability. Species in extreme environments are especially susceptible to climate change; hence, it is important to determine environmental and biological variables that influence their migration. Polar bears (Ursus maritimus) are an Arctic apex carnivore whose migration phenology has been affected by climate change and is vulnerable to future changes. Here, we used satellite-linked telemetry collar data from adult female polar bears in western Hudson Bay from 2004 to 2016 and multivariate response regression models to demonstrate that 1) spatial and temporal migration metrics are correlated, 2) ice concentration and wind are important environmental variables that influence polar bear migration in seasonal ice areas, and 3) migration did not vary across the years of our study, highlighting the importance of continued monitoring. Specifically, we found that ice concentration, wind speed, and wind direction affected polar bear migration onto ice during freeze-up and ice concentration and wind direction affected migration onto land during breakup. Bears departed from land earlier with increased wind speed and the effect of wind direction on migration may be linked to prey searching and ice drift. Low ice concentration was associated with higher movement during freeze-up and breakup. Our findings suggest that migration movement may increase in response to climate change as ice concentration and access to prey declines, potentially increasing nutritional stress on bears.