EasternPurpleMartin_Counting_Balinsky_Andy_AustinTX_8December2022_Reel4137.mp3

Andy Balinsky [00:00:00] It's very difficult to come up with an estimate.

Andy Balinsky [00:00:03] I mean, I've tried various things. So, I mean, the general way to count a flock of birds that's just too numerous to go, "one, two, three, four, five", is to count a patch. You count ten birds, and then you sort of think of, like, if you created a rubber stamp with those ten birds and kind of rubber stamp, rubber stamp that and go, "Okay, one, two, three, three, four, five, six, seven, eight, nine, ten". Okay, that's ten patches of about ten. That's about 100.

Andy Balinsky [00:00:31] And then you repeat that at a bigger scale. So, okay, so that's about, that's about 100 birds in that flock. Then, "One, two, three, four or five". So that's, that's about ... you kind of get an idea of how much space, maybe a thousand birds take up and you rubber stamp that across the sky.

Andy Balinsky [00:00:46] Which would be fine if they were all sitting in one place or, you know, these, they're swirling around and the density isn't uniform. You know, there might be a, it might be thicker over here, and thinner over here. And then a bunch of them land and new ones come in and then something scares them. And they, you know, the ones that were in the trees go swooping up again. So, you know, did I count these already?

Andy Balinsky [00:01:08] And so it's, it's, really, at best, a wild guess. You can probably, probably accurately guess how many zeros there should be. But, as far as what that number at the beginning of it should be, is, is a little difficult.

Andy Balinsky [00:01:21] Another technique I've heard is, and I'm a bit skeptical. I mean, we've had some people from the Purple Martin Conservation Association come down, and I think they've given us some estimates of maybe 100 to 200,000 birds.

Andy Balinsky [00:01:35] There was one Audubon member who had this idea of, like, the martins will come into these roosts from all directions. They tend to go out of the city in the morning, and they feed in these, they feed in the agricultural areas, which tend to have more insects than the city. And then they come back in in the evening. And they'll sort of come in, if you think of the, the directional compass as kind of a clock, you know, you might say, "Okay, so between 12:00 and 1:00, that 1/12 of the sky, if you can count the martins, you can accurately count the martins coming in from that direction by maybe going a few miles out from the roost and count all the martins you can see passing over, because when they're heading to the roost, they're not doing so much swirling. They're, they're generally going one direction. So you can count them once and be done.

Andy Balinsky [00:02:27] You know, so, if you, if you could think, "Well, if I can count all the martins coming from this 1/12 and multiply that by 12, assuming it's they're coming from the same number in all directions, maybe that gives me an estimate."

Andy Balinsky [00:02:39] He observed in one spot and used that to come up with an estimate of 600,000 birds, which I think sounds a bit much. And it's, it's possible that maybe he was looking at a very dense area and maybe other, other wedges of this clock were not quite so dense. And so maybe, you know, maybe multiplying his his wedge by 12. I'm not exactly sure what his technique was, if I'm describing it accurately, but it was, it was that basic idea. I think he came up with a bit of an overestimate.

Andy Balinsky [00:03:09] But, anyway, another thing that people have used sometimes is taking photos and counting after the fact. Just, you know, "Okay, I'm going to take this photo and, you know, take a red pen and mark each of them that way". I know how many birds, but you can't take a 360 fish-eye view at the level of detail that would allow you to snapshot all the martins at one time. So that's also just a way of getting an estimate of one chunk of sky, and then you have to sort of multiply that out.

Andy Balinsky [00:03:41] And then, it's an interesting thing that you see when, you can only really appreciate it when you go to one of these roosts. I mean, you can see what's, what any, any observer would just say, "That has to be tens of thousands of birds just swirling in the sky". And there's, there's multiple layers. Like, you can see what you can see with the naked eye. And, you put your binoculars up and you realize that there are birds higher up that you can't even see with the naked eye. And they're also thick up there.

Andy Balinsky [00:04:07] But, all these birds end up in about seven trees, seven big, seven live oak trees, among probably a few dozen trees at this, well, they have, they've hopped around between several different parking lots lined with oak trees over the years. But they really try to pack into as small a space as possible.

Andy Balinsky [00:04:32] You would think it might be possible to count once they've landed, and they're not moving around, to count them on the trees. And maybe you could, if you could somehow get above them.

Andy Balinsky [00:04:41] But, they're so dense. I mean, they're almost, they're covering almost every surface of it, and there's, there's several layers of them. So I think even that approach would be, would be difficult to count them.

Andy Balinsky [00:04:53] But I think they have, I think they have characteristics like a school of fish, if, if one's ever seen a documentary with this twisting school of fish and the dolphin comes in from the right and the whole school sort of separates around it.

Andy Balinsky [00:05:07] I think what they're trying to do in clustering into so few trees is nobody wants to be the edge bird in case a falcon comes by, or a red-tailed hawk. Everyone wants to be in the middle, so that if danger comes in the night that they're going to grab whoever's on the outside of the pack, the group, the flock.

Andy Balinsky [00:05:27] It makes me wonder. I'm just, I think, I had this thought once or twice before. I don't know if there's any way of weighing a tree, of somehow getting some kind of a, a scale like underneath, like, because that would be inaccurate. I mean, you can figure out how much a martin weighs. So, if you could actually get something under a tree that could sense the amount of weight that gets added to a tree, you might be able to say, "Okay, we've got, you know, 3000 pounds of martin. Each martin weighs a half an ounce. So, therefore this is 250,000 martins."

Andy Balinsky [00:05:58] But I don't know how you get a, I don't know how you get a scale underneath a tree. You might you might have to, you might have to plant an acorn on a scale and wait 30 years. But, but then you have to convince the martins to use that tree.