Hola Tim,
Of course, you were the observer on the scene, so your observations would hold sway over any picture of one moment in time, and we both know how easily one photo can deceive. We apparently don't disagree about photos 10 and 16, that are clearly Violet-green Swallows.
You claim that photos 9 and 12 are Black Swifts, and I respect your call - you were there. I only said that they "appear to be White-throated Swifts," knowing that foreshortening and angle of view can change how the shape of the wings and the cleft of the tail appear in the photograph. In those photographs, they looked too narrow-winged and with a too-deeply cleft tail for Black Swift, but that could easily be just and artifact of those single photographs. Thank you for clarifying.
As for photograph 15, I respectfully have to take issue - again, realizing that you were the observer on the scene, and I can only judge from that single photo. In that photo, none of the birds clearly shows the shape well. The one at the bottom of the photo appears like it could be a swift, but the angles are too distorted to know. The one in the middle (I presume the one that you claim has wings that are too long) looks to me like it's wings are too short, triangular shaped, too bent at the wrist and too wide at the base for a swift. But the one that really swayed me was the one on the upper left, that looks very much like it's wings are folded. I look at that bird and have a hard time seeing how it could be any other way. Now we both know that swifts don't fold their wings in flight, but that swallows frequently do. I have a really hard time imagining how that particular bird could be a swift. But you were there, I wasn't. I'm just commenting on what the photographs look like.
With regards to "the expert," I'm sure you're correct that Ken Rosenberg knows what a Black Swift looks like, but please take a look at the e-Bird reports before taking Bryant to task for questioning the report from someone we all agree is an expert birder. During the time of the ABA convention, there are apparently three major reports of Black Swift, all from the unlikely lower Little Cottonwood Canyon area - no where near the falls where we see them. At that location, clearly you're talking about swifts that are very high-flying. The three reports are of 24, 40, and 65 individuals. The reports from Mr. Rosenberg are of 40 and 65 individuals.
Do you really think there could be a sighting of 65 Black Swifts in Utah? Do you think there are even 65 individuals in the whole state combined? Except for those three ABA convention reports, I can't find a single report in Utah of over 6 individuals. In fact, there aren't any of even close to that number in Colorado - very, very few double digit reports from there, and none anywhere close to 65, or even 40. To make it even more remarkable, I can't find a single report from anywhere in the U.S. of that number. The biggest number I can find was a fall migration sighting at Hawk Hill in Marin Co. California of 43 birds, and a sighting at a known migrant-funnel on the coast of Washington, of 36 individuals, also during fall migration.
So, as far as I can tell, that report of Ken Rosenberg's (and a few other observers) of 65 individuals (at the end of the breeding season) represents the largest number ever reported in the U.S. or Canada. Do you really think it's true?
I do know one thing, the ABA conventions are populated by lots of birders who, frankly, tend to over-rate their own abilities and experience. They also are heavily infected with "hopeful birder syndrome." Even an experienced birder can easily get swept into a hopeful birder euphoria over the sighting of a "life bird" when in the company of a large group of birders desperately wanting to see a bird.
Do I believe that Ken Rosenberg saw at least one or a few Black Swifts? Probably. Did he actually see the most ever reported in the U.S. at the mouth of Little Cottonwood Canyon? Highly doubtful.
Remember, the only real difference between an expert and a beginning birder is that the expert has misidentified many, many more birds than the beginner. As someone who has misidentified many more birds than most folks, I am highly skeptical of the number of Black Swifts reported at the time of the ABA convention, expertise of the observers notwithstanding.
Enjoy the swifts (both the numerous White-throated and the rare Black) up there. In the meantime, I'll wait here for your birds, or ones from the mountains here to come down to the coast, where I did see a flock of about 75 Black Swifts flying low over the palms behind the beach one fall afternoon. Maybe it'll happen again this year.
Mark