Much of the recent changes in North American climate have occurred during the winter months, and as result, overwintering birds represent important sentinels of anthropogenic climate change. While there is mounting evidence that bird populations are responding to a warming climate (e.g., poleward shifts) questions remain as to whether these species-specific responses are resulting in community-wide changes. Here, we test the hypothesis that a changing winter climate should favor the formation of winter bird communities dominated by warm-adapted species. To do this, we quantified changes in community composition using a functional index--the Community Temperature Index (CTI)--which measures the balance between low- and high-temperature dwelling species in a community. Using data from Project FeederWatch, an international citizen science program, we quantified spatiotemporal changes in winter bird communities (n = 38 bird species) across eastern North America and tested the influence of changes in winter minimum temperature over a 22-year period. We implemented a jackknife analysis to identify those species most influential in driving changes at the community level and the population dynamics (e.g., extinction or colonization) responsible for these community changes. Since 1990, we found that the winter bird community structure has changed with communities increasingly composed of warm-adapted species. This reshuffling of winter bird communities was strongest in southerly latitudes and driven primarily by local increases in abundance and regional patterns of colonization by southerly birds. CTI tracked patterns of changing winter temperature at different temporal scales ranging from 1 to 35 years. We conclude that a shifting winter climate has provided an opportunity for smaller, southerly distributed species to colonize new regions and promote the formation of unique winter bird assemblages throughout eastern North America.

The spatial tracking of climatic shifts is frequently reported as a biodiversity response to climatic change. However, species' range shifts are often idiosyncratic and inconsistent with climatic shift predictions. At the community scale, this discrepancy can be measured by comparing the spatial shift in the relative composition of cold- vs. warm-adapted species in a local assemblage [the community temperature index (CTI)] with the spatial shift in temperature isotherms. While the local distribution of climate change velocity is a promising approach to downscaling climate change pressure and responses, CTI velocity has only been investigated on a continental or national scale. In this study, we coupled French Breeding Bird Survey data, collected from 2133 sites monitored between 2001 and 2012, with climatic data in order to estimate the local magnitude and direction of breeding season temperature shift, CTI shift, and their spatiotemporal divergence - the local climatic debt. We also tested whether landscape characteristics that are known to affect climate velocity and spatial tracking of climate change mediated the climatic debt on the local scale. We found a clear spatial structure, together with heterogeneity in both temperature and CTI spatial shifts. Local climatic debt decreased as the elevation, habitat diversity, and the naturalness of the landscape increased. These results suggest the complementary effects of the local topographic patterns sheltering more diverse microclimates and the increasing permeability of natural and diversified landscape. Our findings suggest that a more nuanced evaluation of spatial variability in climatic and biotic shifts is necessary in order to properly describe biodiversity responses to climate change rather than the oversimplified descriptions of uniform poleward shifts.

Protected areas (PAs) are the cornerstones of global biodiversity conservation efforts, but to fulfil this role they must be effective at conserving the ecosystems and species that occur within their boundaries. Adequate monitoring datasets that allow comparing biodiversity between protected and unprotected sites are lacking in tropical regions. Here we use the largest citizen science biodiversity dataset – eBird – to quantify the extent to which protected areas in eight tropical forest biodiversity hotspots are effective at retaining bird diversity. We find generally positive effects of protection on the diversity of bird species that are forest-dependent, endemic to the hotspots, or threatened or Near Threatened, but not on overall bird species richness. Furthermore, we show that in most of the hotspots examined this benefit is driven by protected areas preventing both forest loss and degradation. Our results provide evidence that, on average, protected areas contribute measurably to conserving bird species in some of the world’s most diverse and threatened terrestrial ecosystems.

Global changes are modifying the structure of species assemblages, but the generality of resulting diversity patterns and of their drivers is poorly understood. Any such changes can be detected and explained by comparing temporal trends in taxonomic and functional diversity over broad spatial extents. In this study, we addressed three complementary questions: How did bird taxonomic and functional diversity change over the past 40 years in the conterminous United States? Are these trends non-linear? Can temporal variations in functional diversity be explained by broad-scale changes in climate and vegetation productivity? We quantified changes in taxonomic and functional diversity for 807 bird assemblages over the past four decades (1970-2011) considering a suite of 16 ecological traits for 435 species. We found increases in local bird species richness and taxonomic equitability that plateaued in the early 2000's while total abundance declined over the whole period. Functional richness, the total range of traits in an assemblage, increased due to the rising prevalence of species with atypical life-history strategies and under-represented habitat or trophic preferences. However, these species did not trigger major changes in the functional composition of bird assemblages. Inter-annual variations in climate and primary productivity explained the richness of bird life-history traits in local assemblages, suggesting that these traits are influenced by broad-scale environmental factors, while others respond more to more local drivers. Our results highlight that a comparative analysis of the multiple facets of functional diversity can raise novel insights on processes underlying temporal trends in biodiversity.

The Near Threatened Eurasian black vulture Aegypius monachus is considered highly threatened in Europe, and the species was reintroduced in France between 1992 and 2004. A total of 53 individuals were released, using two methods: immatures were released from large aviaries at the reintroduction site after a stay of several months (the aviary method), whereas juveniles were placed on artificial nests until fledging (the hacking method). The survival rates of released birds were compared to the survival of wild-born offspring through a multi-event capture–recapture analysis accounting for tag loss. Survival rates were higher in adults than in juveniles and immatures (0.98 ± SE 0.02 vs 0.85 ± SE 0.03) and were constant over time. Overall there were no differences in post-release survival between the two release methods: immatures released by the aviary method had a similar survival to juveniles released by the hacking method or born in the wild. Immatures can breed before juveniles, so releasing immatures by the aviary method could accelerate reintroduction settlement and increase population viability. Accurate estimates of post-release survival are essential to improve the reliability of viability analysis of reintroduced populations and the management of such populations.

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By monitoring biodiversity through citizen science programs, volunteers help scientists gather data at unprecedented temporal and geographical scales, and increase their knowledge and awareness of the surrounding biodiversity. While scientific outcomes of such programs may in the long run improve the state of biodiversity by informing environmental policies, direct benefits to biodiversity could arise locally if such experience of nature lead to biodiversity-friendly behaviors in volunteers. However, whether engagement into naturebased CS programs promotes individual behavioral changes remains poorly known. Here, we explored whether sustained participation in a nature-based citizen science program, called the French Butterfly citizen science project, is associated with changes in individual gardening practices. Specifically, using information provided by volunteers (n = 2362, from 2006 to 2013), we quantified gardening practices that directly affect butterflies, through two different indices: provision of nectar resources, and pesticide use. We found quantitative evidence that individual gardening practices shifted with multiyear participation, towards increased provision of nectar resources and decreased use of pesticides. However, the reduction in pesticide use was weakened if the backyard was used to grow fruits or vegetables. Other variables such as the size of the backyard affected gardening practices. This study reveals that participation in a nature-based citizen science program can prompt biodiversity-friendly behaviors, and highlights citizen science not only as a way to collect ecologically sound data but also as a direct conservation tool. Yet, future interdisciplinary research remains critical to overcome factors limiting firm adoption of probiodiversity behaviors.