Friday, January 16, 2009

Unity of science and Turkey Vultures

One of the features that makes science fun to do, and to spectate at, is that the pieces of knowledge all fit together. There's this very large interlocking structure of knowledge that we each try to build more on to. If we're luckier, we find an area where the pieces don't fit together so well. Or, if we're very lucky, get to break open a large chunk and replace it with another of our own construction.

My recent personal illustration is the paper "Movement Ecology of Migration in Turkey Vultures" (link here, full citation and abstract below). The way I know about it is that it cites a paper I was involved in. Now, I know just shy of nothing about turkey vultures (though we seem to have a lot of them around here, that's about my extent of knowledge). Nor do I know about ecology to be publishing on that. So how do ecologists studying turkey vultures come to cite something I've done professionally? Turns out, they were relating the migration of turkey vultures to meteorological conditions. Now meteorology, I know something about, and contributed to a large project that they used to understand their turkey vultures.

The authors merely using the results of our work doesn't make so much for the picture of interlocking pieces. If all they do or can do is take our results, then, effectively, they're just accepting whatever shape piece we meteorologists hand them. But, in principle at least, this is not what they're doing. The authors look in to the migration patterns of the turkey vultures, and its dependance on meteorological conditions. If the analysis were wrong in some way that affected the birds, their data would be showing this. If the analysis winds were too calm (apparently the vultures like a turbulent atmosphere) in the analysis, then the tracking data would show vultures in places the analysis said they shouldn't be.

Here's the real fun. The ecologists would then send a note to the meteorologists who did the analysis and say that there was a problem. The meteorologists' data didn't fit the vulture data, so we have to talk and figure out where the problem was. Maybe it's the vulture data, maybe it's the meteorological analysis, maybe it's both. But the pieces have to fit together. In practice, we didn't get that call (I don't think, have to check with our lead author for certainty). Their results fit with our work. So we have a little bit more confidence that we got things right in ours -- and so do any other users of our work.


Movement ecology of migration in turkey vultures
Mandel, J. T.; Bildstein, K. L.; Bohrer, G.; Winkler, D. W.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 105 (49): 19102-19107 DEC 9 2008

Abstract:
We develop individual-based movement ecology models (MEM) to explore turkey vulture (Cathartes aura) migration decisions at both hourly and daily scales. Vulture movements in 10 migration events were recorded with satellite-reporting GPS sensors, and flight behavior was observed visually, aided by on-the-ground VHF radio-tracking. We used the North American Regional Reanalysis dataset to obtain values for wind speed, turbulent kinetic energy (TKE), and cloud height and used a digital elevation model for a measure of terrain ruggedness. A turkey vulture fitted with a heart-rate logger during 124 h of flight during 38 contiguous days showed only a small increase in mean heart rate as distance traveled per day increased, which suggests that, unlike flapping, soaring flight does not lead to greatly increased metabolic costs. Data from 10 migrations for 724 hourly segments and 152 daily segments showed that vultures depended heavily upon high levels of TKE in the atmospheric boundary layer to increase flight distances and maintain preferred bearings at both hourly and daily scales. We suggest how the MEM can be extended to other spatial and temporal scales of avian migration. Our success in relating model-derived atmospheric variables to migration indicates the potential of using regional reanalysis data, as here, and potentially other regional, higher-resolution, atmospheric models in predicting changing movement patterns of soaring birds under various scenarios of climate and land use change.

Reprint Address:
Mandel, JT, Cornell Univ, Dept Ecol & Evolutionary Biol, Corson Hall, Ithaca, NY 14853 USA.

Research Institution addresses:
[Mandel, J. T.; Winkler, D. W.] Cornell Univ, Dept Ecol & Evolutionary Biol, Ithaca, NY 14853 USA; [Mandel, J. T.; Bildstein, K. L.] Acopian Ctr Conservat Learning, Orwigsburg, PA 17961 USA; [Bohrer, G.] Ohio State Univ, Dept Civil & Environm Engn & Geodet Sci, Columbus, OH 43210 USA

3 comments:

EliRabett said...

Excellent point.

The converse of this is the incoherence of denial. Those who are closing their eyes and trying to imagine that humans are not causing the climate to change quote three, or four or five mutually contradictory ideas, papers, or imaginings.

No better example than what happened recently on Marohasy's blog when the top ten papers (denying climate change) were a nest of contradictions.

As a commenter said
"You have missed the point. On this post(by Cohenite) he has used contradictory science to demonstrate that AGW is not real. You cannot use one paper to falsify one aspect, and then another paper to falsify another, when the two papers are mutually exclusive.

He attempted to show that the Greenhouse effect is negligable. He posted a paper he said showed why (Minschwaner), it contradicts earlier an earlier paper he posted (Miskolczi). one claims there is a greenhouse effect due to greenhouse gases, tthe other claims it is due to optical depth. You can’t have it both ways.

Skeptics use a scatter shot approach, using one kind of physics to ‘disprove’ one aspect and an opposing kind of physics to ‘disprove’ another. You need to have an internally consistent argument."

Hank Roberts said...

> the vultures like a
> turbulent atmosphere

So do all gliders, especially those of us who can't flap even if we want to. (I began flying hang gliderers about thirty years ago.)

I'd bet you or they could look up the lapse rate -- the data is provided by the weather service and much used by sailplane pilots among others -- for this.

The monarch butterflies in migration pass over and stop off on my favorite hang gliding mountain; likely tracking them will show the same sort of effect.

Hank Roberts said...

Distinguish weather with a lapse rate, which you could consider 'organized' turbulence -- that's what gets you thermals, gliders of all sorts circling and climbing then heading off toward the horizon to pick up another thermal further along, and go distance.

And there's plain old turbulent weather, "chaotic" weather, which is just messy and treacherous. Smart fliers stay out of it.

With climate discussions, there's the kind where there are differences that are productive.

And there's the kind where folks get together in fellowship who have utterly incompatible beliefs and contradictory facts. They are, all together, in opposition to climate science. As long as they waste time and confuse people, they're winning in their own terms.