Virus host shifts from managed honey bees, Apis mellifera, are thought to contribute to the decline of wild pollinators. However, data on the impact of such viruses on wild pollinators remain scarce, and how landscape structure may affect virus transmission is poorly understood. We experimentally deployed bumble bee colonies in an agricultural landscape to study changes in the bumble bee virome under varying habitat composition and configuration. The results show a decline in prevalence and viral loads of honey bee associated viruses, while viruses common in Bombus spp. increased during field exposure. Honey bee associated viruses had no effect on colony development, suggesting that immediate impacts are unlikely in the field. Notably, we further demonstrate that increased habitat diversity results in fewer viruses in Bombus colonies. To mitigate the decline of bumble bees and other wild pollinators, we suggest focusing conservation efforts on habitat diversification and restoration.

Body size of individuals is typically increasing towards colder and higher latitudes, as larger body size is known to be a thermoregulatory adaptation to colder circumstances. Here we explored the spatio--temporal changes in wing length and body weight of 24 wintering bird species in Northern Europe and how these relate to annual changes in winter temperature. We show that across all species, body size has decreased since the 1970s, with a negative relationship between wing length and temperature anomalies of previous winters, suggesting carry over effects likely linked with body size--related survival or dispersal. Body weight was negatively related with the temperature anomaly of the same winter, indicating more immediate effects related to reduced fat reserves during mild winters. Our results highlight climate--driven decrease in body size across several species and its' association with annual variation in winter temperature in the high latitudes.