What are the mystery drones in Colorado up to?

Over the past couple weeks many drones have been spotted over the plains of eastern Colorado at dark until about 10 PM. No one knows who they belong to or what they are doing. I am wondering if the HN community has any ideas.

More info: https://www.msn.com/en-us/news/us/its-creepy-unexplained-drones-are-swarming-by-night-over-colorado/ar-BBYwMD8