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Understanding the demographic drivers of range contractions is important for predicting species' responses to climate change; however, few studies have examined the effects of climate change on survival and recruitment across species' ranges. We show that climate change can drive trailing edge range contractions through the effects on apparent survival, and potentially recruitment, in a migratory songbird. We assessed the demographic drivers of trailing edge range contractions using a long‐term demography dataset for the black‐throated blue warbler (Setophaga caerulescens) collected across elevational climate gradients at the trailing edge and core of the breeding range. We used a Bayesian hierarchical model to estimate the effect of climate change on apparent survival and recruitment and to forecast population viability at study plots through 2040. The trailing edge population at the low‐elevation plot became locally extinct by 2017. The local population at the mid‐elevation plot at the trailing edge gradually declined and is predicted to become extirpated by 2040. Population declines were associated with warming temperatures at the mid‐elevation plot, although results were more equivocal at the low‐elevation plot where we had fewer years of data. Population density was stable or increasing at the range core, although warming temperatures are predicted to cause population declines by 2040 at the low‐elevation plot. This result suggests that even populations within the geographic core of the range are vulnerable to climate change. The demographic drivers of local population declines varied between study plots, but warming temperatures were frequently associated with declining rates of population growth and apparent survival. Declining apparent survival in our study system is likely to be associated with increased adult emigration away from poor‐quality habitats. Our results suggest that demographic responses to warming temperatures are complex and dependent on local conditions and geographic range position, but spatial variation in population declines is consistent with the climate‐mediated range shift hypothesis. Local populations of black‐throated blue warblers near the warm‐edge range boundary at low latitudes and low elevations are likely to be the most vulnerable to climate change, potentially leading to local extirpation and range contractions. [ABSTRACT FROM AUTHOR]

Although long-distance migratory songbirds are widely believed to be at risk from warming temperature trends, species capable of attempting more than one brood in a breeding season could benefit from extended breeding seasons in warmer springs. To evaluate local and global factors affecting population dynamics of the black-throated blue warbler ( Setophaga caerulescens), a double-brooded long-distance migrant, we used Pradel models to analyze 25 years of mark-recapture data collected in New Hampshire, USA. We assessed the effects of spring temperature (local weather) and the El Niño Southern Oscillation index (a global climate cycle), as well as predator abundance, insect biomass, and local conspecific density on population growth in the subsequent year. Local and global climatic conditions affected warbler populations in different ways. We found that warbler population growth was lower following El Niño years (which have been linked to poor survival in the wintering grounds and low fledging weights in the breeding grounds) than La Niña years. At a local scale, populations increased following years with warm springs and abundant late-season food, but were unaffected by spring temperature following years when food was scarce. These results indicate that the warming temperature trends might have a positive effect on recruitment and population growth of black-throated blue warblers if food abundance is sustained in breeding areas. In contrast, potential intensification of future El Niño events could negatively impact vital rates and populations of this species. [ABSTRACT FROM AUTHOR]

We review the observed and potential effects of climate change on native fauna of forests in northeastern North America by focusing on mammals, birds, amphibians, and insects. Our assessment is placed in the context of recent regional-scale climate projections. Climate change, particularly in recent decades, has affected the distribution and abundance of numerous wildlife species. Warming temperatures, alterations to precipitation regimes, seasonality, and climatic extremes are projected to affect species directly or indirectly in each of the focal taxa. Greatest climate change will occur during winter, and the survival of winter-active species as well as the survival, distribution, and abundance of hibernating mammals, amphibians, resident birds, and diapausing insects may be altered. Even under low emissions scenarios, effects on native fauna may be profound, affecting iconic species, endangered species, and species that provide economically valuable services, such as pollination and regulation of insect populations. However, much research that is essential to assessing the effects of climate change on the native fauna of northeastern forests remains to be done. Research that reveals causal mechanisms and relates these findings to population and community level processes will be most valuable. [ABSTRACT FROM AUTHOR]

Insect abundances are declining in many areas around the world, but the causes of those declines are seldom clear. Here we report a dramatic decline in the abundance and diversity of Coleoptera (beetle) taxa in a large tract of intact northern hardwood forest during the last 45 years, and provide evidence supporting winter warming as the primary cause. Beetles were sampled using the same method (window traps) and in the same locations within the Hubbard Brook Experimental Forest, New Hampshire, in 1973–1977 and again in 2015–2017. The mean (±SE) number of beetles captured per 48-h fell from 23.2 (±3.89) to 3.9 (±1.19), a decline of 83% over this 45-year period. The number of beetle taxa captured decreased by 39%, with 19 beetle families disappearing entirely. Beetle capture rate was least when and where climate was warmest. Capture rate was significantly lower in the 2010s when mean daily temperature was about 1.8 °C warmer, and sampling during 2016–2017 at low, mid and high elevations (320, 540, and 810 m asl, respectively) revealed lowest beetle captures at low elevation where climate was warmest. Most importantly, beetle capture rate was significantly lower after winters with less snow cover during the previous winter, indicating that snow cover in northern hardwood forest is essential for sustaining the beetle community. These results imply that additional climate warming might further reduce the abundance and diversity of beetles and other arthropods inhabiting the forest-floor, potentially affecting critical ecosystem processes such as decomposition and carbon storage. • Coleoptera abundance and diversity dropped steeply between mid 1970s and mid 2010s. • Beetle abundance, all taxa combined, declined by 83% between the sampling periods. • The number of taxa detected was 39% less in 2015–2017 compared to mid 1970s. • Predaceous beetles declined the most. • Reduced snow depth and duration were identified as the major causes of the declines. [ABSTRACT FROM AUTHOR]