In my 30 plus years of living in Des Plaines (1/2 mile from the DP River and close to a city park), I usually enjoy a number of evenings watching 'fall' migrating Common Nighthawks from our patio. The higher numbers usually are the last full week of August, but I do also see them before and after that week of course.
With time to just sit out this afternoon (5 pm off and on until sunset), read the paper and check for nighthawks and other birds, I was pleasantly surprised to see a few flocks of nighthawks heading south, my first of the season. I only saw a rare nighthawk in the spring, so glad I am seeing them already.
I had a few small groups of migrating Chimney Swifts (totalling 12 or more) early in the evening.
Then (6:26pm) I caught glimpse of a decent flock of Nighthawks fairly low over my house and heading west towards the park. From there they circled a bit (likely found a thermal) raised up to pretty much out of sight, and headed south. I counted at least 26 in this group.
Later I did note a group of 3 (6:31pm) and at least 14 over Arndt Park about 6:45. Did not see any while checking off and on until past sunset.
Seeing my first flock a bit earlier than usual this year, and hope to see more in coming nights when the winds (and insects) are favorable for more flights.
Keep your eyes open, and enjoy!
Alan