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Tactics and Vectors 98/99 |
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Looking For Monarchs From an UltralightAircraft in Texas School of Higher Learning Thoughts of a white-knuckled zoology professor flying an ultralight aircraft a mere
50 metres above Texas --- as in the hard range of it --- while desperately looking for
migrating monarch butterflies. Apart from asking myself what will happen if my engine
quits, and can I make that hayfield up ahead, my main question is, why can't I see the
butterflies? They were up there this morning when I took off. How can they just vanish
like that?
My obsession with flight took hold one day in 1974 --- before I began studying monarchs. It was one of those pamphlets they hand out in malls that got me, the one claiming that it's easy, fun and affordable to learn to fly gliders. I had nary a question then. By the following May I was a licensed glide pilot. but it quickly became apparent that acquiring the skill to soar with the butterflies was going to take awhile. Other pilots could remain aloft for hours. My flights averaged 15 minutes. By 1977, I managed to extend only a few to over 30 minutes. Then, one September day, I glanced out of my office window to see a monarch soaring in circles as it effortlessly rode a thermal up and over the building. Impressed, I decided to study their flight tactics. After all, I rationalized, as a behavioural ecologist it was within my field of study. Of course, the added bonus was that I might pick up some a few tips on flying. I figured the key to gaining a better understanding of the monarch's flight tactics was to characterize the thermal updrafts they exploited. The solution for that seemed obvious. All I had to do was build a powered ultralight aircraft (to keep me in the sky longer than 15 minutes), add a few extra instruments, then fly in the vicinity of the migrants. Thus I would have my critical data. But it didn't work. It took me another frustrating season of research to understand why I could fly amidst a hoard of migrants and not see them. Of course! All my equipment and theories about air currents could not help me see what amounted to a piece of paper set on edge against the horizon and a camouflaged one at that. Look down, no butterflies. Look ahead and to the side, ditto. I finally realized that I could see them if I looked up, but that isn't a very safe way to fly. Especially at low altitudes. At least I came to understand something about the turbulence that I encountered that morning in Texas. It was a category of wind shear caused by the meteorological phenomenon called nocturnal inversion. the inversion forms at night when the air cools near the ground, then abruptly breaks up in the morning as the air heats up, producing dangerous, rolling, wind shear. the butterflies 'know' about this and had flown up to exploit the abundant lift generated by the breakup. When I blundered into the break, I had nearly flipped over. In the 20 years since that monarch soared past my window, I've spent many hundreds of hours observing their migration and still have only a rudimentary understanding of their complex flight tactics. In matters of of flight, you could say I've always been a slow learner. In retrospect, the monarch's superior skill isn't surprising. I've been at this game for only 23 years. My teachers have been gliding and soaring across the continent for some 12,000 years. The proceeding article appeared in the "Reflections"
section of Seasons, Summer 1997, Vol 37, No. 2, page 46. |