Gwenyn Brodorol (Native Bee in Welsh)

This is a large native bee of some kind, but I don’t know what its name is. It’s the same size as a bumblebee, but longer, with a more greenish color. It was really working the sunflower and had pollen on its back instead of its legs. I’m seeing fewer bees as the temps are dropping at night. Leaves are starting to turn yellow and I’ve seen a few dead bumblebees on the ground.