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1. Drought influences habitat associations and abundances of birds in California's Central Valley

   https://doi.org/10.1111/ddi.13827  

   Goldstein, Benjamin R. ; Furnas, Brett J. ; Calhoun, Kendall L. ; Larsen, Ashley E. ; Karp, Daniel S. ; de Valpine, Perry ( March 2024 , Diversity and Distributions)

   As climate change increases the frequency and severity of droughts in many regions, conservation during drought is becoming a major challenge for ecologists. Droughts are multidimensional climate events whose impacts may be moderated by changes in temperature, water availability or food availability, or some combination of these. Simultaneously, other stressors such as extensive anthropogenic landscape modification may synergize with drought. Useful observational models for guiding conservation decision‐making during drought require multidimensional, dynamic representations to disentangle possible drought impacts, and consequently, they will require large, highly resolved data sets. In this paper, we develop a two‐stage predictive framework for assessing how drought impacts vary with species, habitats and climate pathways.

   Central Valley, California, USA.

   We used a two‐stage counterfactual analysis combining predictive linear mixed models and N‐mixture models to characterize the multidimensional impacts of drought on 66 bird species. We analysed counts from the eBird participatory science data set between 2010 and 2019 and produced species‐ and habitat‐specific estimates of the impact of drought on relative abundance.

   We found that while fewer than a quarter (16/66) of species experienced abundance declines during drought, nearly half of all species (27/66) changed their habitat associations during drought. Among species that shifted their habitat associations, the use of natural habitats declined during drought while use of developed habitat and perennial agricultural habitat increased.

   Our findings suggest that birds take advantage of agricultural and developed land with artificial irrigation and heat‐buffering microhabitat structure, such as in orchards or parks, to buffer drought impacts. A working lands approach that promotes biodiversity and mitigates stressors across a human‐induced water gradient will be critical for conserving birds during drought.

    

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2. Facilitation alters climate change risk on rocky shores

   https://doi.org/10.1002/ecy.3596  

   Jurgens, Laura J. ; Ashlock, Lauren W. ; Gaylord, Brian ( December 2021 , Ecology)

   A huge fraction of global biodiversity resides within biogenic habitats that ameliorate physical stresses. In most cases, details of how physical conditions within facilitative habitats respond to external climate forcing remain unknown, hampering climate change predictions for many of the world’s species. Using intertidal mussel beds as a model system, we characterize relationships among external climate conditions and within‐microhabitat heat and desiccation conditions. We use these data, along with physiological tolerances of two common inhabitant taxa (the isopodCirolana harfordiand the porcelain crabPetrolisthes cinctipes), to examine the magnitude of climate risk inside and outside biogenic habitat, applying an empirically derived model of evaporation to simulate mortality risk under a high‐emissions climate‐warming scenario. We found that biogenic microhabitat conditions responded so weakly to external climate parameters that mortality risk was largely unaffected by climate warming. In contrast, outside the biogenic habitat, desiccation drove substantial mortality in both species, even at temperatures 4.4–8.6°C below their hydrated thermal tolerances. These findings emphasize the importance of warming‐exacerbated desiccation to climate‐change risk and the role of biogenic habitats in buffering this less‐appreciated stressor. Our results suggest that, when biogenic habitats remain intact, climate warming may have weak direct effects on organisms within them. Instead, risk to such taxa is likely to be indirect and tightly coupled with the fate of habitat‐forming populations. Conserving and restoring biogenic habitats that offer climate refugia could therefore be crucial to supporting biodiversity in the face of climate warming.

    

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3. The functional significance of facultative hyperthermia varies with body size and phylogeny in birds

   https://doi.org/10.1111/1365-2435.13274  

   Gerson, Alexander R. ; McKechnie, Andrew E. ; Smit, Ben ; Whitfield, Maxine C. ; Smith, Eric K. ; Talbot, William A. ; McWhorter, Todd J. ; Wolf, Blair O. ; Williams, ed., Tony ( January 2019 , Functional Ecology)

   Facultative hyperthermia, the elevation of body temperature above normothermic levels, during heat exposure, importantly affects the water economy and heat balance of terrestrial endotherms. We currently lack a mechanistic understanding of the benefits hyperthermia provides for avian taxa.

   Facultative hyperthermia has been proposed to minimize rates of water loss via three distinct mechanisms: M1) by maintaining body temperature (T_b) above environmental temperatures (T_e), heat can be lost non‐evaporatively, saving water; M2) by minimizing the thermal gradient whenT_e>T_b, environmental heat gain and evaporative water loss rates are reduced; and M3) by storing heat via increases inT_bwhich reduces evaporative heat loss demands and conserves water.

   Although individuals may benefit from all three mechanisms during heat exposure, the relative importance of each mechanism has not been quantified among species that differ in their body size, heat tolerance and mechanisms of evaporative heat dissipation.

   We measured resting metabolism, evaporative water loss and real‐timeT_bfrom 33 species of birds representing nine orders ranging in mass from 8 to 300 g and estimated the water savings associated with each proposed mechanism. We show that facultative hyperthermia varies in its benefits among species.

   Small songbirds with comparatively low evaporative cooling capacities benefit most from (M1), and hyperthermia maintains a thermal gradient that allows non‐evaporative heat losses. Other species benefited most from (M2) minimizing evaporative losses via a reduced thermal gradient for heat gain at highT_e. We found that (M3), heat storage, only improved the water economy of the sandgrouse, providing little benefit to other species.

   We propose that differences in the frequency and magnitude of hyperthermia will drive taxon‐specific differences in temperature sensitivity of tissues and enzymes and that the evolution of thermoregulatory mechanisms of evaporative heat dissipation may contribute to differences in basal metabolic rate among avian orders.

   Understanding the mechanistic basis of heat tolerance is essential to advance our understanding of the ecology of birds living in hot environments that are warming rapidly, where extreme heat events are already re‐structuring avian communities.

   Aplain language summaryis available for this article.

    

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4. An inverse latitudinal gradient in infection probability and phylogenetic diversity for Leucocytozoon blood parasites in New World birds

   https://doi.org/10.1111/1365-2656.13117  

   Fecchio, Alan ; Bell, Jeffrey A. ; Bosholn, Mariane ; Vaughan, Jefferson A. ; Tkach, Vasyl V. ; Lutz, Holly L. ; Cueto, Victor R. ; Gorosito, Cristian A. ; González‐Acuña, Daniel ; Stromlund, Chad ; et al ( October 2019 , Journal of Animal Ecology)

   Geographic variation in environmental conditions as well as host traits that promote parasite transmission may impact infection rates and community assembly of vector‐transmitted parasites.

   Identifying the ecological, environmental and historical determinants of parasite distributions and diversity is therefore necessary to understand disease outbreaks under changing environments. Here, we identified the predictors and contributions of infection probability and phylogenetic diversity ofLeucocytozoon(an avian blood parasite) at site and species levels across the New World.

   To explore spatial patterns in infection probability and lineage diversity forLeucocytozoonparasites, we surveyed 69 bird communities from Alaska to Patagonia. Using phylogenetic Bayesian hierarchical models and high‐resolution satellite remote‐sensing data, we determined the relative influence of climate, landscape, geography and host phylogeny on regional parasite community assembly.

   Infection rates and parasite diversity exhibited considerable variation across regions in the Americas. In opposition to the latitudinal gradient hypothesis, both the diversity and prevalence ofLeucocytozoonparasites decreased towards the equator. Host relatedness and traits known to promote vector exposure neither predicted infection probability nor parasite diversity. Instead, the probability of a bird being infected withLeucocytozoonincreased with increasing vegetation cover (NDVI) and moisture levels (NDWI), whereas the diversity of parasite lineages decreased with increasing NDVI. Infection rates and parasite diversity also tended to be higher in cooler regions and higher latitudes.

   Whereas temperature partially constrainsLeucocytozoondiversity and infection rates, landscape features, such as vegetation cover and water body availability, play a significant role in modulating the probability of a bird being infected. This suggests that, forLeucocytozoon, the barriers to host shifting and parasite host range expansion are jointly determined by environmental filtering and landscape, but not by host phylogeny. Our results show that integrating host traits, host ancestry, bioclimatic data and microhabitat characteristics that are important for vector reproduction are imperative to understand and predict infection prevalence and diversity of vector‐transmitted parasites. Unlike other vector‐transmitted diseases, our results show thatLeucocytozoondiversity and prevalence will likely decrease with warming temperatures.

    

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5. Consumer roles of small mammals within fragmented native tallgrass prairie

   https://doi.org/10.1002/ecs2.3441  

   Hope, Andrew G. ; Gragg, Sabrina F. ; Nippert, Jesse B. ; Combe, Fraser J. ( March 2021 , Ecosphere)

   Grassland ecosystems globally are being negatively impacted by changes in climate, disturbance regimes, nutrient flux, and consumer guilds. Changes in the trophic ecology of consumers can substantially influence local resources, contributing to shifting diversity, community turnover, and other processes of ecosystem change. Small mammals are diverse and abundant within grasslands and yet the impact of changing ecosystems on small mammals and the role of these mammals as consumers are still both under‐studied. We assessed small mammal resource use within grassland and woodland vegetation types that have resulted from landscape‐scale experimental disturbance through fire treatments within the tallgrass prairie ecoregion of the North American Great Plains. We predicted that resource use would vary significantly among grassland vs. woodland communities, in turn reducing the role of small mammals in contributing to future maintenance of native prairies. We sampled five dominant species of rodents across three years and multiple habitats. Using stable isotope analysis, we investigated isotopic niche area and overlap to infer variation in diet, both within and among species. Resource use shifted in bivariate isotopic space seasonally but not across years when combining all species and habitats. Inferred spring diet (based on fur samples) was highly diverse and overlapping. Summer isotopic values (based on liver tissue) in woody habitat treatments were narrower and overlapped less than within grassland habitats. Consumers generally shifted from C₄herbivory to C₃herbivory, or greater omnivory, when analyzing grassland, shrubland, and woodland habitats respectively. Within the tallgrass prairie ecosystem, small mammal populations in herbaceous‐dominated habitats use a broader variety of resources than small mammals in proximate woody‐dominated habitats. As native grasslands experience woody encroachment, small mammal assemblages experience turnover of dominant species and associated changes in diet. Ecosystem changes such as cessation of frequent fire resulting in more woody habitats may include reduced roles by native small mammals as consumers/dispersers/propagators of native grassland plants.

    

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