Ornithological Sociology (or, Birds On a Wire – In a Snowstorm)

I am privileged to have a regular watering hole where the help treats me with the utmost respect, and (to bring to mind a simpler time) a bit of deference. Said watering hole also gives me a vantage point from several directions to observe the behaviour of one of our species of sparrow.
I write this in the midst of one of the best (or worst, depending) snowfalls we’ve seen in a few years. Mercifully, at least it shall, in part, mitigate the opportunity for wildfires in the area for the upcoming summer.
During my brief visit, I was pleased to watch several individuals of what I will initially call ‘chipping sparrows’, since they resemble greatly individuals of that species with which I became familiar in the flatlands roughly 2500 miles east. They’re a fun, if skittish, bird to watch.
There were roughly twenty individuals, mostly males (as far as I could tell, my eyesight being what it is nowadays). I was on an outdoor patio, watching them congregate (in what I approximate as thirty to thirty-two degree temperatures, with a breeze approximately 10 knots, and intermittent snow) in an aspen approximately 25 feet high. After their usual jostling for tree position (a separate topic), they congregated over the period of three minutes on two power lines within my view.
Being able to watch the order of congregation was quite interesting, and I believe I have gleaned at least a small part of the reason (mostly by extrapolation from Richard Dawkins’ Selfish Gene).
I was able to observe (subjectively, of course) that mating pairs (of which I estimated as three) were closest to each other, by comparing their physical distance to that of the other individuals on the two lines. I also noted that where there were pairs, latecomers to the line walk would insinuate themselves next to those I identified as the females in the mating pairs. Those females who received such attention tended to scoot toward the mate which with they had arrived.
I also noted that the endmost individuals had more separation from other individuals than did the mated pairs, or the other prospective suitors. The endmost also seemed to be the least likely to be aggressive toward the mated pairs, or any other females.
Dawkins’ theory of ‘bird census’, in my extrapolation, is also a mating census.
I am also going out on a bit of a limb to say that mated pairs use a version of ‘iris recognition’ to ensure that the nearest individual of the opposite sex is their previously-accepted mate. Since there are no actual sounds coming from any of these birds, there is either a pheromone recognition, or (since they do seem to interact visually) some sort of visual pattern recognition.
I have to determine some way of scientifically distinguishing what visual cues this species uses to discriminate.

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