With over half of earth's terrestrial biota living beneath forest canopies, our ability to accurately capture organism–climate relationships in forested ecosystems is imperative for predicting species' vulnerability to future climate change. Assessing the vulnerability of forest dependent species, however, hinges on quantifying microclimates that exist below the forest canopy and might be influenced by varying levels of disturbance in human‐modified landscapes. The goal of our study was to examine the multi‐scaled predictors of subcanopy microclimate variability across a heterogeneous landscape in Midwestern USA during winter, and to further evaluate whether a widely available interpolated climate model accurately captures this variability. By deploying a network of temperature sensors along a fragmentation gradient, we found that forests in more fragmented landscapes with greater amounts of forest edge and increasing distances between forest patches, experienced colder minimum and average daily temperatures throughout the winter than forests in less fragmented landscapes. We found that greater tree densities and higher elevations led to warmer microclimates while increasing distances from urban centers led to colder microclimates. The negative effect of forest edge on minimum temperatures was lessened by the effect of increasing basal area, highlighting the importance of local‐ and landscape‐scale features on microclimate heterogeneity. Temperature discrepancies between subcanopy microclimates and climate interpolations were influenced by many of the same features, and could be of a similar magnitude as those predicted by future climate change scenarios. Using a biological threshold based on metabolic and demographic constraints for winter birds, we found that the variability in microclimates along our forest fragmentation gradient (50 km) was comparable to the magnitude captured by weather stations across a latitudinal gradient spanning more than 650 km. Our results suggest that biophysical properties of landscapes can alter spatial gradients of microclimates and should be considered when assessing species' vulnerabilities to future climate change.

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Agricultural intensification is a leading threat to bird conservation. Highly diversified farming systems that integrate livestock and crop production might promote a diversity of habitats useful to native birds foraging across otherwise‐simplified landscapes. At the same time, these features might be attractive to nonnative birds linked to a broad range of disservices to both crop and livestock production. We evaluated the influence of crop–livestock integration on wild bird richness and density along a north‐south transect spanning the U.S. West Coast. We surveyed birds on 52 farms that grew primarily mixed vegetables and fruits alone or integrated livestock into production. Crop–livestock systems harbored higher native bird density and richness relative to crop‐only farms, a benefit more pronounced on farms embedded in nonnatural landscapes. Crop–livestock systems bolstered native insectivores linked to the suppression of agricultural pest insects but did not bolster native granivores that may be more likely to damage crops. Crop–livestock systems also significantly increased the density of nonnative birds, primarily European Starlings (Sturnus vulgaris) and House Sparrows (Passer domesticus) that may compete with native birds for resources. Models supported a small, positive correlation between nonnative density and overall native bird density as well as between nonnative density and native granivore density. Relative to crop‐only farms, on average, crop–livestock systems exhibited 1.5 times higher patch richness, 2.4 times higher density of farm structures, 7.3 times smaller field sizes, 2.4 times greater integration of woody crops, and 5.3 times greater integration of pasture/hay habitat on farm. Wild birds may have responded to this habitat diversity and/or associated food resources. Individual farm factors had significantly lower predictive power than farming system alone (change in C statistic information criterion (ΔCIC) = 80.2), suggesting crop–livestock systems may impact wild birds through a suite of factors that change with system conversion. Collectively, our findings suggest that farms that integrate livestock and crop production can attract robust native bird communities, especially within landscapes devoted to intensified food production. However, additional work is needed to demonstrate persistent farm bird communities through time, ecophysiological benefits to birds foraging on these farms, and net effects of both native and nonnative wild birds in agroecosystems.

Understanding how individual differences in physiological performance modify behavioral responses to environmental variability and its fitness consequences is key to predicting the vulnerability of species and populations to environmental change. For many species, summit metabolic rate (MSUM; the upper limit to heat production) and basal metabolic rate (BMR; the lower limit related to energy acquisition and processing) often constrain aspects of physiological performance and behavioral activity. We examined the relationship between metabolic phenotypes, foraging behavior, and survival in overwintering black‐capped chickadees Poecile atricapillus inhabiting contiguous and fragmented forested landscapes. We found that birds with lower summit metabolic rates were generally more sensitive to winter weather and increased their use of supplemental feeding stations as ambient temperatures decreased. In highly fragmented forests, this relationship may have incurred strong survival consequences, as birds with lower summit metabolic rates were less likely to survive the winter season. Additionally, we found that chickadee populations persisting in fragmented landscapes were characterized by slightly higher thermogenic capacity (MSUM) and lower maintenance metabolic costs (BMR). We suggest that habitat loss and fragmentation present unique selection pressures that alter the relationships between environmental variability, behavior and physiology, and result in context‐specific fitness consequences.

Projected increases in the variability of both temperature and precipitation will result in the greater likelihood and magnitude of extreme weather (e.g., cold snaps, droughts, heat waves) with potential implications for animal populations. Despite the ecological consequences of extreme weather, there are several challenges in identifying extreme events and measuring their influence on key demographic processes in free‐living animals. First, there is often a mismatch between the spatial and/or temporal resolution of biological and climate data that could hinder our ability to draw accurate inferences about how species and populations respond to extreme events. Second, there are multiple approaches for identifying an extreme event ranging from statistical definitions (e.g., standardized deviates) to species‐specific biological thresholds. Lastly, the impacts of extreme weather on species can vary as a function of differences in exposure and intrinsic sensitivity to climate variability. In the Northern Hemisphere, rapid warming has contributed to a “wobblier” jet stream that promotes the higher likelihood of cold Arctic air moving southward and leading to more extreme winter conditions. Due to these conditions, the Upper Midwest experienced two of the coldest winters in the past 35 yr during 2014 and 2015. We combined radiofrequency identification technologies with fine‐scale weather data and standard capture–mark–recapture analyses to estimate weekly and overwinter survival rates of a common winter passerine, the Black‐capped Chickadee (Poecile atricapillus), in a near continuous fashion. Using both statistical and biological definitions of weather extremes, we found that declining ambient temperatures reduced survival (despite the presence of favorable microclimates), and that biologically defined thresholds of extreme weather were better at explaining variation in survival than statistical ones. Moreover, habitat fragmentation interacted with temperature to modify the exposure of birds to extreme weather with survival consequences, but sensitivity, as measured by body condition, did not appear to play a significant role. These results provide a novel contribution to the understanding of how extreme weather may interact with local‐ and landscape features to influence the demography of species and populations, and suggest potential opportunities for climate‐change adaptation in human‐dominated landscapes.