Thrills and Trills: mating dance!

Yesterday around 4 pm I saw my first mating dance of the 2015 season.  I was sitting quietly in the lower garden observing a couple of feeders close to the bluff edge (my slow recovery from pneumonia requires a lot of resting!), when I observed a hummingbird doing his unmistakable "pendulum dance" in and above the wild cherry tree (Prunus serotina) right in front of me. When I realized what was going on I activated the Vixia G30 video camera and pointed it, zoomed out, at the general area of activity. Of course because I have it permanently set up with a 2X digital zoom it cannot capture a very wide field of view, so the video only shows the central, lowest, part of the dance - presumably where the target of the dance, most likely a receptive female, was located. However, I could not spot the female, partly because I, like she, was mesmerised by the dance. The U-shaped arc seemed to go much higher than the tree-top, though I could not follow the complete swing. As he came downward, near the nadir of the dance (close to the presumed female) he emitted a distinct  brief "trilling" sound presumably created by the air rushing through the tail feathers (see http://www.berkeley.edu/news/media/releases/2008/01/30_hummingbird.shtml).  Here's the video followed by my Youtube description:-

This movie shows a hummingbird mating dance, at the Baiting Hollow Hummingbird Sanctuary, shot on may 4 2015. The male arrived a week before and established a breeding territory and the female presumably only on may 4. You have to quite carefully to see the male doing his U-shaped "pendulum" dance, and even more closely to see the perched female near the base of his dance (i.e. the bottom of the U). In fact, it's impossible to spot the female, unless you watch carefully near the end where the male does a final close swing, and then, after a short delay, the female takes off to the lower right. In fact, you have to slowly, frame by frame, rewind the movie so you can see the spot where the female starts her rightward departure. Then you realize that the female was perched at that spot throughout the dance, intently turning to follow the male's dance. The movie was shot with the camera "overcranking" - i.e. it's shot at 60 fps for playback at 30 fps, giving a 2X slow motion effect. Because the male, then the female, are moving very rapidly, they shift position from frame to frame very quickly. Unfortunately I don't think standard Youtube allows you to rewind the movie backwards, frame by frame (see Note below), so you can identify the female's takeoff spot. But I can do this using Quicktime, and it's quite clears she is perched at that spot until the point, near the end, where the male's dance stops and she takes off to the lower right. I also show, below, an excerpt from this movie, at 4X slo mo. My Vixia G30 allows overcranking, but unfortunately in this mode the sound is switched off. However I could clearly here a trilling sound that the male emitted (probably using his tail feathers) as he reached the base of his dance and starts to accelerate upwards. 
Added Note: you can add a frame-by-frame advance/rewind app to Google Chrome (https://chrome.google.com/webstore/de...) that will allow you to rewind the video frame by frame from the moment the female takes off to the lower right, so you can find out where exactly she is perching during the male's dance. You can also make out how she moves her head/body while perched to follow the male's dance. Note that she's just a speck in a quite large tree, and it's essential you use the full 1080P HD setting.

Here's the second, 4X slo-mo, excerpt showing the end of the male's dance followed by the female's departure to the lower right.

This is a short extract from the video "hummingbird mating dance may 4", shot at the Baiting Hollow Hummingbird Sanctuary.  It shows the last part of that movie, at 4X slo-mo. The female is perched at the same spot throughout the longer movie, and is turning to follow, with great interest, the "pendulum" mating dance of the male. Then near the end, as the male finishes his dance, she quickly leaves her perch, flying off to the lower right, presumably to where the male is waiting for her. It's almost impossible to spot where she is perching either in the full movie or in this slowed excerpt. You have to look for moment where she suddenly takes off to the lower right, and then rewind the movie slowly backward from that point. You will see exactly where she takes off from, and then you realise that she's actually at that location (but very hard to spot) throughout the excerpt and, I think throughout the full movie (which shows only the second half of the full mating dance). During the filming I could not actually see the female, she's a tiny almost immobile (other than her rapid head-turning to follow the male) dot on a thin branch, and I did not clearly see her rapid departure either.But I suspected that she must have been there, and quite close to the nadir of the dance. Indeed, in this excerpt you can see that the last swing of the male is actually very close to where the female sits, though previous swings were not quite so close. Use this Chrome app to add frame-by-frame advance/reverse to YouTube: https://chrome.google.com/webstore/detail/frame-by-frame-for-youtub/elkadbdicdciddfkdpmaolomehalghio. You can also see the feeder just below where the female is perching. Note that the female takeoff starts during the 29 second of the movie, and the male's last swing is closest to the perching female during the seond second of the movie (i.e. during the frames marked 1). Thus during 28/4 = 7 seconds the female comes to realize that the male has finished his dance and is waiting for her somewhere below the right bottom of the video.

Note that the pendulum dance is also used by hummmingbirds (I think males only) as an aggression display, eg towards immature hummers. However in my experience this is usually a more fragmentary type of dance. I think that in this case it's more likely to be a true courtship display, given the size of the arc covered, the presence of a hummer (most likely a newly arrived adult female) at the nadir of the dance, and above all the trill. However, I did not see the "shuttle dance" that usually follows the courtship pendulum dance, and preceded actual mating - perhaps because this happened somewhere down on the bluff. Let's hope that this courtship was consummated (off-screen, like an old-fashioned Hollywood movie) and that the female successfully nests nearby.  

I will now try to create annotated versions of these 2 videos, pointing out the key features to look at. 

UPDATE: looking at this vid more carefully I see that the male executes one more swing from right to left, at the 10/(4) sec mark. This swing passes below the female, quite close to the feeder, and he disappears below the bluff, to the left of the frame. This explains the otherwise strange lapse of time between what is the penultimate swing above the female and the female's departure to the lower right. Note that the total actual duration of this movie excerpt is around 7 seconds, so there's a lot happening very fast. Also note that in individual frames the moving hummers are blurred because of the relatively slow shutter speed (not sure what the exact speed is because the camera was in Programmed mode; I will try to shoot more video using a fast (eg 1/1000 speed) but of course this demands intense lighting.