The acute decline in global biodiversity includes not only the loss of rare species, but also the rapid collapse of common species across many different taxa. The loss of pollinating insects is of particular concern because of the ecological and economic values these species provide. The western bumble bee ( Bombus occidentalis ) was once common in western North America, but this species has become increasingly rare through much of its range. To understand potential mechanisms driving these declines, we used Bayesian occupancy models to investigate the effects of climate and land cover from 1998 to 2020, pesticide use from 2008 to 2014, and projected expected occupancy under three future scenarios. Using 14,457 surveys across 2.8 million km 2 in the western United States, we found strong negative relationships between increasing temperature and drought on occupancy and identified neonicotinoids as the pesticides of greatest negative influence across our study region. The mean predicted occupancy declined by 57% from 1998 to 2020, ranging from 15 to 83% declines across 16 ecoregions. Even under the most optimistic scenario, we found continued declines in nearly half of the ecoregions by the 2050s and mean declines of 93% under the most severe scenario across all ecoregions. This assessment underscores the tenuous future of B. occidentalis and demonstrates the scale of stressors likely contributing to rapid loss of related pollinator species throughout the globe. Scaled-up, international species-monitoring schemes and improved integration of data from formal surveys and community science will substantively improve the understanding of stressors and bumble bee population trends.

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As urbanization continues to transform landscapes, it is imperative to find ways to conserve biodiversity within fragmented habitats. Forest interior dwelling birds are particularly vulnerable to development pressures because they require large tracts of forest to support their life cycles. Although Barred Owls (Strix varia) are frequently described as an obligate mature forest species, they have been found in urbanized landscapes. To determine if certain habitat characteristics, such as mature trees, facilitate the presence of Barred Owls in developed regions, we modeled Barred Owl occupancy probability along a development gradient in the Piedmont region of the southeastern United States. We surveyed for owls by broadcasting conspecific calls to solicit response and by passively recording at survey sites using autonomous recording units. Detection/nondetection data were collected during the breeding season and analyzed within an occupancy framework to investigate patterns of habitat association in our region, while allowing for imperfect detection of owls. Average tree height was the best predictor of Barred Owl occupancy across a development gradient, regardless of forest coverage. We did not find Barred Owl occupancy to decline with increasing impervious surface density. Our research implies that developed landscapes containing mature urban trees can support breeding populations of Barred Owls. Des caractéristiques clés d'habitat facilitent la présence de Chouettes rayées dans les paysages urbanisés RÉSUMÉ. L'urbanisation transformant en continu les paysages, il est impératif de trouver des façons de conserver la biodiversité dans les milieux fragmentés. Les oiseaux qui fréquentent l'intérieur des forêts sont particulièrement vulnérables à l'étalement urbain parce qu'ils ont besoin de grands parterres forestiers durant leur cycle annuel. Bien que les Chouettes rayées (Strix varia) soient souvent décrites comme des espèces de forêts matures strictes, elles ont pourtant aussi été trouvées dans des paysages urbanisés. Afin de déterminer si certaines caractéristiques de l'habitat, tels que les arbres matures, facilitaient la présence de chouettes dans les régions urbanisées, nous avons modélisé la probabilité d'occurrence de cette espèce le long d'un gradient d'urbanisation dans la région du Piedmont dans le sud-est des États-Unis. Nous avons inventorié les chouettes en diffusant des enregistrements de chants de conspécifiques afin de susciter une réponse, et passivement, en enregistrant au moyen d'enregistreurs automatisés à des sites d'inventaire. Les données de détection/non-détection ont été récoltées durant la saison de nidification et analysées dans le contexte d'un modèle d'occurrence pour investiguer les tendances dans l'association espèce-habitat dans la région, tout en tenant compte de la détection incomplète des chouettes. La hauteur moyenne des arbres s'est avérée la variable la meilleure pour prédire la présence des Chouettes rayées le long d'un gradient d'urbanisation, peu importe le couvert forestie...