BlogArchive-11/06
Harveys Knob Blog
This site is for matters related to the Harveys Knob Hawkwatch which has been a hawk migration datapoint since 1977. The emphasis is on the study of the behavior of hawks in migration. And other things as they come up.
Monday, November 27, 2006
More .......
Bijam wrote:
Seen this?
>
http://www.ideasbypaul.ca/research_5d.pdf
>
Thermals.....
All of that sounds good, but does it take into consideration that thermal activity cannot be accurately forecast and that the hawkwatcher is limited to a two mile radius purview? Naturally, there are more hawks found where thermals are strongest but does that mean that the hawks found represent the maximum that could be found? What are the counts three or four miles away and what is the thermal strength there?
And how much money does each hawkwatching site have to donate in order to acquire the precious instruments that would help forecast this thermal activity?
We hawkwatchers are sort of fixed into our site parameters and we have to know which meteorological conditions coupled with the topography of the site will produce the maximum number of hawks. And, we do not need to know this ahead of time but after the flight has passed. For, we volunteer, amateur, hawkwatchers are not really studying the true numbers of migrating hawks but rather the study of the behavior of hawks in migration.
The BLIP maps would be good for the study of the behavior of hawks in migration but they would not be good for predicting a good site for the study of the behavior of hawks in migration for various reasons. Nor
would they be good for predicting when to go to study the behavior of hawks in migration.
DJ
Posted by Blogknobber at 9:29 AM 0 comments
Saturday, November 25, 2006
Dr. Holt Responds
In my continuing and seemingly futile effort to find a variable that brings hawks to our site, I continually analyze counts and weather data and send speculation to our resident raptoclimactomigratologist who indulges my general thickheadedness for no apparent reason. The last post reflects this speculation and I followed this up with some more data from that day which I thought reflected a ‘lift event’. Here is his response to that data:
Bijam wrote:
See anything in these graphs?
I don’t see anything in these graphs for the simple reason I don’t know what to look for. I do not believe that the daily or hourly variations in the weather have any influence on the hawk migration. I will have to see a mountain of evidence before I change this admittedly biased opinion.
Try to think like a hawk which is not thinking at all. It is feeling and reacting without any conceptualizing. For instance: A hawk rises in the valley to proceed south and it feels strong NW winds. It knows from experience, or from the genes, that now is the time to move to the highest point in view, nothing more and nothing less. Once it reaches the highest point it will find the ridge lift that will expedite its southward journey. If the highest point becomes a long ridge stretched out over a large expanse of land from NE to SW it will provide a collection point for all those hawks rising that same morning. A hawkwatcher stationed on that ridge will enjoy a good day. The hawk felt and reacted and the hawkwatcher was there because he knew the hawk would only feel and react.
Otherwise, the hawkwatcher would have been at WRNC [Woodpecker Ridge Nature Center - a valley floor observation point]. Or take the southern Michigan site into consideration. We both know that there is no high point in this territory, so the hawk does not move anywhere but to the southwest even when the winds are very strong northwest. This is because the hawk has it built into him to migrate to the southwest regardless of the conditions and it helps that the hawk presents a flying object that exhibits near zero drag coefficient to the wind. This is why they can migrate under strong winds in flat terrain and why some species can hover motionless in the face of strong winds while searching for prey. And, the reason for the southwest determination is in the genes.
When the migration is flying on thermals the hawk has no plan to fly on thermals, as it cannot plan. It finds a thermal when it rises by observing other flying creatures or by accident. When it finds a thermal and begins to soar it will find other hawks that found that thermal in precisely the same manner. Then they break out of the thermal and they spread out over a large piece of terrain in what we hawkwatchers call a stream. The width of that stream helps them to locate the next thermal and the process repeats itself. Sense and react, and sense and react only.
No migrating hawk ever watches the Weather Channel nor does it have a topographical map of the terrain over which it is to travel. It knows only to fly to the south and to utilize any condition that facilitates that flight that it senses during that flight. Its southerly flight may be influenced by its sensing the earth’s magnetic field which causes its flight to be more southwesterly than southerly. The genes say south and the conditions say southwesterly. It is all sense and reaction.
It is interesting to speculate upon the sky conditions when the highest counts of migrants have passed the lookout. Cloud forms and winds are important. But, is the altitude of the flight important? I am speaking of the flight that everyone assumes is too high to see that goes past the lookout undetected. It is quite possible for the human eye to detect a Broad-winged hawk at ¾ of a mile distance with the naked eye. I think I can safely estimate that 90% of the hawks seen at any lookout are within the purview of the human eye. Is there any reason to believe that there is a massive flight of migrating hawks flying beyond the purview of the human eye?
I think not. Three quarters of a mile is equal to 3960 feet. The naked eye migrant at Harvey’s Knob is flying 6484 feet above sea level. Most solar induced thermals have cap clouds in the 6000 to 8000 feet above
sea level range. In some places even lower altitudes are encountered. And, most of the migrants are seen within that range. None are seen above that range for the simple reason that the cap clouds obscure visibility. It is easy to speculate on migrating hawks flying into towering cumulus clouds in order to gain altitude as well as to evade the hawkwatcher’s scrutiny. But, will the migrant expose himself to the turbulence and wind sheer of a towering cumulus in order to gain an altitude it does not need or to evade the hawkwatcher’s scrutiny it knows nothing of.
If the hawks are flying too high to be detected by the hawkwatcher and if they always do this on days when the hawkwatcher has nothing to report, then what is the purpose of reporting what the hawkwatcher has seen. If the hawks fly too high to be detected then the hawkwatching reports cannot possibly measure the population density of the hawks. The only purpose of reported hawkwatches are to provide an alibi for each hawkwatch rather than a piece of evidence that may someday have an effect on the art of hawkwatching. Resolve this contradiction and you have made an important step toward elevating the art of hawkwatching to the science of hawkwatching.
In the meantime, I prefer to remain close to the ground. I prefer to remain in that realm where the most hawks migrate, that realm where most of us hawkwatchers can see. I prefer to concentrate my mental efforts into what I can see or otherwise experience. That realm consists of solar induced thermals and ridge lift. Other systems of rising air are inferior because they are spread out over too wide an area of land. An upper air disturbance creates a low pressure cell which causes air to rise over a very large area of land. Any opportunistic migrant will take advantage of this rising air but it will not mean anything to the not so oppurtunistic migrant.
I have seen Broad-winged hawk migrating on weak rising air because the Broadwings are in a hurry. But, the Red-tailed hawk is not in such a hurry and I have never seen Redtails migrate on puny rising air. We know that Redtails migrate in large numbers when the conditions are conducive to their migration and we must realize that ten to twenty Redtail migrants mean nothing insofar as the science of migration is concerned. Probably, half of those Redtails are locals that will be in the area all winter. There is no-way to distinguish between local Redtails and migrant Redtails in late November.
I hope I have touched on all your questions in this diatribe as I do not have anything more to say, and if I did I don’t have the energy to do so.
Posted by Blogknobber at 10:06 AM 1 comments
Wednesday, November 22, 2006
11/19/06 Migrants of another color
Tad was on the watch today and it was an unusual day. Hawks were slow in the morning, some accipiters and redtails, and then suddenly a group of 4 ravens went over high, heading northward. Then some Red Shouldereds came up from the valley and then Redtails were high and moving. Then we had a string of these:
Another Loon stream came later, but spread out like the above. Then, along came a small group of these:
Quite a surprise to see Canadas on the mountain.
To complete the unusual day we had a V of these:
Swans, no less.
Unusual day!
I heard on the news later that there was an upper level disturbance that caused some “lift”.
What’s that about?
Posted by Blogknobber at 11:32 AM 2 comments
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