It is now August, a dry and hot month in New England. While it may seem early to say the Hummingbirds are leaving anyone that photographs them can see the decline in numbers already.
Many of the males have moved on already. In any given group of birds you might find a single male.
The flowers here have gone by or are starting to. The woods still have the small wild flowers, however Hummingbirds burn food so fast they often eat 1.5 to 3 times their body weight in food per day! In order to gather enough nectar, they must visit hundreds of flowers every day.
When they leave New England they keep going south until they hit Mexico or Central America. With a trip like that they probably should have left some time ago.