More time to fly: with a warming climate the Western honey bee (Apis mellifera, Linnaeus) now has more temperature-eligible flight hours than 40 years ago

There have been official NOAA and EPA reports of measurable changes in temperature across the United States over the last several decades with average temperatures increasing in most areas and decreasing in a few others. In order to fly, honey bees need optimal temperatures ranging from 13 degrees C (55 degrees F) to 38 degrees C (100 degrees F), sunlight, low wind, and no rain. This study looks at changes in temperature-eligible flight times of honey bees across the US and Canada. Four decades of weather data from 60 locations in the US and Canada for the period 1980 through 2019 were analyzed. We discovered that honey bee flight hours are increasing almost everywhere, but most dramatically in the northern regions of Canada and Alaska, and also in a few locations in the US south of the border with Canada. Warming temperatures (ignoring all other factors), may lead to more flight time for honey bees; may affect plant bloom times and species distributions; and may change the exposure of honey bee colonies to pests, parasites, and pathogens. Therefore, beekeepers must be prepared to modify management practices to accommodate possible plant-pollinator mismatches and timings for seasonal and pest management. This study highlights that a warming climate will increase temperature-eligible flight hours for honey bees. Further research is needed to consider how other climate change factors, in combination with temperature, will affect actual honey bee flight opportunities and behavior, as well as, overall colony management.