Thanks for all your comments. Next time I'm in Mexico, I will definitely do my best to get some video footage. My recollection of what I saw in October 2005 in Mazatlan is that the various yaws and compensations were easy to see, as you say. I can't remember how long the formations were stable - perhaps generally less than a minute, before the formation would break down (but I'm really just guessing) - but they were long enough to see the dynamics involved. And after the formations broke down, they would often reform again fairly soon.
Regarding Phil's comment that the Mazatlan colonies were possibly just different from the Cancun colonies I will need to investigate that. (Frank - I was in Cancun over Christmas, by the way and the migration habits might be a factor involved in when and why they engage in vee formation - something else to investigate). It seems, though, it is unlikely that a single colony in Mazatlan would have developed the vee formation capacity completely independently of a colony in Cancun, especially when the distance between them is not really that great when we think in terms of bird migratory habits. So far, I still think the wind conditions are more likely what prevented vee formation in Cancun, but of course I will need a bit more evidence to support that. Also, Phil, I would argue that strong leadership is not a factor in vee formations. As we all know, self-organized phenomena arise without leaders to guide the emergent patterns - I can't think of why it would be any different for frigatebirds. The formations must self-organize from some principle of interaction - in the case of organisms that save energy by drafting, it is the coupling between them that occurs because there is a physiological or energetic advantage to their coupling (ie. to their drafting). It could be that frigatebird vee formations are simply derived from their inherent natural behaviours and have no basis in any underlying physical principles, but given the advantages conferred upon other types of organisms that engage in drafting dynamics and formations, it seems reasonable to ask if there is there is a physical principle underlying the formations. Nonetheless, what this all suggests to me that it is an area ripe for further study, and that very little work has been done to establish the universality of the "drafting principle" as I am calling it. I actually think it applies in a lot of other situations as well, from trail formation to aspects of economics, but that's little more than a gut feeling at this point. But I suppose, at the very least, until I can get some good footage of frigatebird formations and some wind speed measurements, we can only speculate as to what is happening with them. I'm not sure when I'll be in Mexico next, but I'll keep everyone posted as to what I see. If anyone else is going, please keep an eye out for the frigatebirds! Pelicans also fly in vees too, but they are more like geese, I think - they fly past at fairly high speed. On the note about the decline of traveling geese, I really can't speculate. I live on the west coast of Canada in British Columbia and I still see vee formations going in all directions. But perhaps global warming is a factor in the distances they need to fly now - maybe they can stay farther north all year round. Hugh Trenchard ----- Original Message ----- From: "Carl Tollander" <[EMAIL PROTECTED]> To: "The Friday Morning Applied Complexity Coffee Group" <friam@redfish.com> Sent: Friday, January 05, 2007 10:16 PM Subject: Re: [FRIAM] observations of complex phenomena while in Mexico > Curious. I was wondering if, since the frigatebirds are aligning into > formations without > flapping, if it would be easier to perceive if there were differences in > the "yaw" of the > bird wing or body relative to its position in the formation. If so, > several hypotheses > about aerodynamics on formation might be arise. If, for example, there > was a pronounced > yaw to the right on the right side of the V due purely to the drafting > aerodynamics of the > V (this is just an example) then the bird in its local frame might be > adjusting its position > relative to the bird in front, which would be somewhat to the left of > where it "should" be, > (given the local aerodynamic properties of the surrounding air > (temperature, pressure, wind speed, etc) > so the bird would work harder to adjust its position so that the bird in > front would be > more in the expected position. At some point the energy advantage gained > by remaining > in the V formation would be lost, and the V would not be supportable. > > Frigatebirds are relatively large, so the idea here is that any drafting > effect would not occur > uniformly on any given bird in a V formation, possibly causing various > local yaws and compensations. > > Carl > > Hugh Trenchard wrote: >> I am a lurker on this listserv and find many of the discussions here >> interesting and valuable. Recently I was in Mexico and noticed a couple >> of >> interesting complex phenomena I thought I would share with this group. >> >> The first relates to frigatebird formations and ties in with observations >> of >> these birds I made last year. Last year, when in Mazatlan, I noticed >> that >> frigatebirds often hover and glide for several minutes at a time without >> flapping and that they tend to glide in disorderd configurations until >> they >> spontaneously undergo a phase change (it seems to me) when they align in >> vee >> formations - still gliding nonetheless. These are fantastic sights to >> see, >> since the birds seem to hang in the air in these vee formations without >> passing across the sky at the relatively high speeds of geese, for >> example. >> >> This year, in Cancun, I noticed frigatebirds gliding in disordered >> configurations and, waiting patiently for the phase change, I was >> disappointed when these changes did not occur. I wondered if I was >> imagining the alignments I saw last year in Mazatlan, but fairly certain >> I >> wasn't, I speculate why the phase changes did not occur among the birds I >> saw in Cancun. Firstly it's possible the frigatebird colonies on the >> Caribbean side of Mexico simply don't undergo these formations, being a >> slightly different sub-species or what have you. Perhaps, but I >> hypothesize >> that the wind speeds are the primary factor in determining whether >> formation >> phase changes occur. >> >> In Mazatlan last year in late Sept/early October, the wind speeds were >> low, >> I recall. In Cancun, wind speeds were significantly higher. I suggest >> that >> gliding in vee formations can only occur between a certain range of wind >> speed - if wind speed is too low, the birds cannot glide at all; if too >> high, they can glide, but they cannot align in vee formations. The >> critical >> range allows frigate birds to draft when gliding behind another while >> maintaining position, but above the range the drafting effect is too high >> and the birds get "sucked" through - or tend to fall, it looked to me - >> the >> low pressure areas and cannot hold their positions. >> >> Drafting ordinarily has the effect of saving energy (a la cyclists in a >> peloton), but if birds are gliding and already saving substantial energy >> by >> not flapping their wings, I wondered whether any significant energy >> savings >> benefit can be derived by aligning in vee formations while gliding. At >> first I thought not, but gliding inevitably requires some energy - small >> muscle coordination and positional adjustments - not as costly as >> flapping >> wings, but some energy is required. When frigatebirds form vees, I >> hypothesize there is in fact significant energy savings for those birds >> in >> drafting positions - small muscle contractions for positional adjustments >> may be reduced, and birds in these formations will expend less energy. >> They >> would not, I suggest, align in these ways if it were not for some energy >> savings benefit. >> >> Because frigatebirds do not generate the higher air pressure behind which >> to >> draft, such as geese do, or cyclists do, or fish in water do by >> propelling >> themselves through the medium (air or water), I suggest this form of >> energy >> savings constitutes a third type of "drafting". The other is energy >> reduction by huddling, such as penguins undergo. So I suggest three >> types >> of drafting occurrences: >> >> I Occurs when system components generate effective air or >> liquid pressure as they propel themselves through the medium; eg. cyclist >> pelotons, fish schools, geese in vees; >> >> II Occurs when system components remain stationery and air >> or >> liquid pressure is generated externally; eg frigatebirds in vees while >> gliding and remaining more or less positionally stable, and possibly some >> types of fish (here I suggest this may occur in fish swimming upstream, >> such >> as salmon, which may hold themselves in a stationery position against the >> flow of the water - I haven't specifically observed any interesting >> drafting >> formations as a result, although I have watched salmon swim upstream and >> speculate drafting formations do occur) >> >> III Occurs when system components remain stationery and >> environment temperature drops; eg. penguin huddles >> >> Type I exhibit phase changes from disordered states to ordered states and >> back again through hysteresis loops. For cyclists, when peloton speeds >> are >> higher than a critical speed/drafting threshold, disorder in the peloton >> occurs. In a peloton, density is generally higher at low speeds and >> density >> decreases as speeds increase. At a relatively high threshold speed, a >> peloton loses cohesiveness entirely. To resume cohesion, peloton speeds >> must fall to a lower threshold to resume cohesive formations (I've >> observed >> and documented this). The loop is clockwise (speed on Y axis, >> density/order >> on X) , but is the inverse of vehicle traffic hysteresis, for example, >> where >> density increases as speed decreases (note that drafting is not a factor >> in >> traffic). >> >> For frigatebirds, because order increases as windspeed increases to a >> threshold range, above which disorder occurs, wind speeds must only drop >> to >> within the critical range for order to occur again. As a result the >> hysteresis loop may not exist or is not as evident. I tentatively >> speculate >> this windspeed range is approximately equivalent to the magnitude of >> drafting benefit derived when birds are in drafting formations; similarly >> the height of the hysteresis loop in drafting cyclists is related to the >> drafting benefit derived (but may not precisely match it). >> >> So drafting parameter seems to represent a constant that manifests itself >> in >> related but different ways. For example, in Type 1 situations, drafting >> parameter indicates the magnitude of the hysteresis loop; in Type II >> where >> there is no hysteresis, drafting parameter indicates the magnitude of the >> critical range of speeds within which certain formations occur. Drafting >> parameter is thus also a general principle underlying the self-organized >> complex behaviour of a number of different systems. >> >> For Type III (penguin huddles), density/order increases as temperature >> drops >> (requiring greater energy output to remain warm, so a decrease in >> temperature is equivalent to an increase in speed in Type I situations); >> density/order decreases as temperature increases to some threshold, after >> which there is no huddle cohesion. Presumably at some very cold >> temperature >> the huddle cannot generate enough heat and disintegrates by penguins >> freezing to death. In the direction of temperature increase, the >> hysteresis >> loop occurs when disorder occurs at a critical temperature, but must fall >> to >> some lower threshold temperature for the huddle to occur again. >> >> In any event there is a lot more analysis to be made, and I have more to >> say >> even now, but here are a few observations. Basically, my point is that >> through my frigatebird observations, I've identified a third type of >> drafting situation. I had already identified the peloton (which is >> obvious >> and well documented) and huddle situations (which is not as obvious and >> not >> well documented). _____________ >> >> The second, slightly less rigourous observation I made when in Cancun was >> a >> clustering effect among cabs. In Cancun, and likely many parts of Mexico, >> all cabs are required to be of the same colors, so they are all easy to >> spot. There are also many, many cabs in Cancun - it appears about one in >> six vehicles is a taxi. >> >> On the roads, it appeared to me that frequently cab clusters, or several >> cabs near each other, would be driving within two degrees of each other, >> often within one degree. One explanation is that they often originate in >> the same location, many waiting at high person-density locations like the >> airport, the bus station, etc. However, I am not sure this explains the >> clustering on the roads, as cabs leaving from high density locations >> would >> not leave simultaneously when fares are widely distributed in time; they >> also do not have the same destinations. So, clustering must be due to >> something else, I think. >> >> Firstly, cab drivers tend to drive faster than the rest of the traffic, >> especially when they have a fare on board. I am wondering if their fast >> driving and deft abilities at weaving in and out of traffic allows them >> to >> agglomerate at stop lights. As traffic approaches stop lights, the >> slower >> driving traffic still leaves enough space for faster traffic further away >> from the light to slip through and make up a few spaces, even as traffic >> closest to the stop lights slow down and increase density. After a few >> such >> lights, faster traffic "sifts" through to the front, and ends up at the >> front. This is just an idea, and no doubt there are a number of problems >> with it (for example if cabs also tend to go through yellow and red >> lights, >> reducing agglomeration). Nonetheless, if the phenomenon is real - and I >> observed it to occur more often than just chance would seem to explain - >> then there must be a reason for it. >> >> In any event, I would be interested in any input others may have about >> both >> of these subjects. >> >> >> >> >> >> >> ============================================================ >> FRIAM Applied Complexity Group listserv >> Meets Fridays 9a-11:30 at cafe at St. John's College >> lectures, archives, unsubscribe, maps at http://www.friam.org >> >> >> >> > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > lectures, archives, unsubscribe, maps at http://www.friam.org ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org
