The Chimney Swifts have finally arrived in Fort Peck. A couple of days ago I found a few foraging over a pond near the Missouri River and yesterday I found a couple of them back at the chimney at the old school building across the street from my Mom and Dad's house. Tonight there were a bunch of them flying in courtship formations around the house.
The website Chimney Swifts.Org has a map of first observations of the year for the North American continent as well as a pile of information on Chimney Swifts, including a information on building a Chimney Swift tower. You can see the progression of the northward migration here.
I like this photo because you can see the tail spines fairly well. A few years ago I had the opportunity to band a Chimney Swift and I was impressed and surprised with the spines on the ends of the tail feathers.