I have yet to witness the Nighthawk migration in Vermont.  Stowe just doesn’t seem to be on their route.  However, if you want to watch a video of their migration, check out the footage of this year’s passage of these birds over the Florida Keys Hawk Watch.  
They recorded 4275 birds on Sept. 10.
Liz Lackey

4275 Nighthawks! | Florida Keys Hawkwatch