These small swallows are among our most beautiful. Their name comes from the violet on top of the rump and the green on the upper back.
I found this bird building a nest in a large root wad lodged along the bank of the Yellowstone River within Yellowstone National Park, but I've also seen them high in the mountains far from any water.
These are such gorgeous birds. As noted above, this bird was building a nest in a tree root wad that had washed down the river during a high water period. He would perch on this broken off root each time he returned with nesting materials, before dropping down a couple feet to his nest site. On this particular occasion, he came in with these long, flowing grass blades that were streaming in the the stiff breeze. I paused for a couple of seconds then started rapid firing photos hoping to capture him just as he started to fly again. This was the best shot I could have hoped for and is one of my favorite all time shots.