Million Bird March
Tis the season for many birds to get the hell out of Dodge (Dodge being the high latitudes) and book to warmer climes to sip mai-tais and fruity drinks in tropical locations (mai-tais and fruity drinks being insects and fruits that don’t die in the winter). There’s a lot we don’t know or are just finding out about migration, one thing being the calls bird make while moving. Cornell is doing some interesting research to that end. Here’s a recent article from the New York Times that gives a layman’s explanation on just what they’re doing.
It’s a interesting read and I encourage you to check it out, but one quote in particular struck me. From the article:
“Last night,” Miyoko Chu, director of publications at the [Cornell Lab of Ornithology], told me on Sept. 10, “a million Swainson’s thrushes” flew over central New York.
A million? Doesn’t that seem like a lot? That has to be just an estimate because how could they count that? When I first read it I thought she meant the city of New York, but now I’m not so sure it’s the state. But it’s not like Cornell has a reputation for exaggerating evidence or anything. It sounds like she estimated the total population of Swainson’s Thrushes and divided by an arbitrary migratory time frame. Or maybe she counted calls for a certain time period (ignoring that the same bird could call more than once) and multiplied by 8 hours. Or maybe the newspaper just misquoted her and she meant “possibly” a million of “nearly” a million. Reporters have a tendency to misquote bird people. Ultimately it’s just picking nits, I’m sure a lot of Swainson’s Thrushes flew over New York (city and state) that night, and many individual birds are never seen by humans in their entire life so it’s difficult to accurately gauge large populations like that. Still though, a million? In one night? Get outta here…
In other news, the newest I and the Bird is up at The Nightjar. Go look at it, and read it too if you’re so inclined. I don’t have anything super exciting in the hopper this weekend, at least not compared to the last two, but I’ll be out looking for a few of those million Swainson’s Thrushes around here with hopefully enough to report on next week. Have a birdy weekend.
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I’m pretty sure Cornell has a station in central New York for monitoring nocturnal flight calls. So by measuring their density over a period of time, they can probably come up with a good estimate of what is passing overhead.
That would explain where they got the data, but I still wonder a bit about interpretation. In that are they counting every individual call note as an individual bird? Even if half the birds call twice that effects the total significantly.
It’s nit-picking really, there are likely lots and lots of Swainson’s Thrushes passing overhead. But I can’t help but wonder whether a million is legit or dramatic effect for a newspaper article. If it’s real it’s pretty incredible.
Also, let’s say that you are monitoring nocturnal flight calls and know the birds flying over are largely Swainson’s Thrushes. Then you look at the Doppler radar and notice a very high concentration of birds on radar at the exact same time. Putting two plus two together….you get a million Swainson’s Thrushes. I think it’s possible that the data could be fairly accurate.
Also, you can’t make a blanket statement about all Cornell ornithologists either. Sure they have made a sizeable mistake as you have addressed very well in previous posts, but you know as well as I do that there is a lot of very reliable and important ornithological data coming out of that university.
Even looking at Doppler you’d only see birds, not individuals. And it still doesn’t take into account if birds call more than once. Say the birds called twice, that means only 500,000 individuals. That’s still enough to show up on Doppler and certainly no small number of birds, but not a million.
The crack about the IBWO wasn’t meant as a slight to all Cornell ornithologists, just a good-natured ribbing, which is fair as long as the organization stands as a united front behind their terrible woodpecker data. Of course they do good work otherwise.