Common Nighthawk
Credit: Tom Vezo

Every year as the hot and humid days of summer ease into the dry warm days of early fall, the nighthawks appear.   In the eastern U.S. at that point in the evening when the setting sun lights up the landscape, there appears in the sky dozens sometimes even hundreds of large silent, dark, knife-winged birds.  They fly quickly and erratically with sudden twists and turns. When one comes close enough you may see the white patch in the wing.

Common Nighthawks have virtually completely disappeared as nesters across the eastern U.S.  and these migrants that pass through in Augusts and early September must certainly be coming from the Boreal.  Although I cannot prove it, I suspect that the timing of the southward migration may be tied to an annual seasonally abundant food source - flying ants.  At this time of year on dry warm days, ant colonies send out their drones and queens for their pioneering attempts to found new ant colonies.  The number of flying ants must be mind boggling across the northeast U.S. through August and September.  I can't really imagine how abundant they must be but you see them everywhere.  The last summer day we went swimming in our favorite lake, the water's surface was covered with millions of them - the fish were going crazy with the feast - that had been blown into the water on their mating flight.  These millions of ants could be the perfect food source for those nighthawks to use to fatten-up and power their long journey to South America where they seemingly disappear into the wilds of the Boreal's sister, the Amazon Basin.

Flying Ant 
Credit: Jeff Wells

Here's a video I found on YouTube of a Common Nighthawk darting around the sky in a similar fashion. You can tell how quick the bird is twisting and turning based on the camera-holder's difficulty in keeping it in the frame!