Heard several of these birds this past summer in the Flathead National Forest near Kalispell, MT and Glacier National Park. These bird calls became very active starting in the evening and lasted throughout the night until near sunrise. I believe we saw one near Glacier National Park. It may have had a white underside and may have been slightly larger than a swallow. This also might not have been the correct bird though. Time of year was early to mid-June.Best times to hear in the video are at 0:23, 0:27, 0:34, 0:45, and 0:53. The volume will probably need to be turned up.