[obol] booming of Common Nighthawks

[pamela johnston]

After being questioned about the "booming" behavior of the Common Nighthawks 
I reported seeing today, I read up on it and now have more questions than 
answers.

What Steve and I saw was a male CONI stooping at another CONI several times 
as they flew. The male was well above the other bird, the sex of which I 
never noted, stooped at and came very near the back of the lower bird, 
booming as it veered off. The other changed course a little with each 
'boom." There was no chasing or other interaction. This was happening while 
three birds were foraging around noon.

Of the references I have on hand, the fullest description of the mating 
display is in The Birder's Handbook; others give only parts of it. The male 
flies around above the intended nest site, calling, then drops nearly to the 
ground and produces the boom with its feathers, "almost crashing near 
mate...Male lands, spreads tail, rocks body, [and makes other body gestures 
while on the ground]. Aerial display and booming continue throughout 
nesting." The authors say courtship occurs "oft at dusk."

So it appears to me that this was an "aerial display" though not the full 
courtship display. It looked more like the harassment of a raptor by a 
smaller bird than any courtship I'm familiar with, so we felt we were seeing 
the male driving off a competitor.

Any thoughts?

Pamela Johnston