12/05/2007
Flying South
Here’s the latest leafy update from my part of New Jersey. I started this column on Sunday, December 2. At daybreak there were two or three inches of snow on the ground and my outside thermometer registered only 21 degrees Fahrenheit. The snow and cold temperature made the roads very slippery and our Sunday papers weren’t delivered until about three hours past the normal time. In recent columns I’ve been remarking about the leaves on the trees in our area hanging on longer than usual. Even today, December 5, there are still some trees in our neighborhood with a nearly full complement of yellow leaves, even some green ones. However, around our house the leaves are down and I do feel comfortable should our guys come to do their final gutter cleaning and lawn blowing/raking.
Lest you think I’ve been overemphasizing our late leaf demise, Sunday’s Star-Ledger contained an article by Rudy Larini headlined “Never-ending fall plays havoc with leaf collection around state”. Ironically, I think fall ended here on Sunday with a city snowplow making its first visit to our street. The article quotes Mark Vodak, a forestry specialist at Rutgers University, as saying that the reason for the abnormal leaf behavior is due to the late warm weather slowing down the decomposition of chlorophyll. The average temperature in New Jersey in October was 62.4 degrees, over 8 degrees higher than normal! The article notes that, all over the state, public work crews have had to extend their schedules because of the late leaf fall.
With wintry temperatures finally settling in, all those birds favoring warmer climes should certainly have left our area or at least started their flights south. On the next page of Sunday’s Star-Ledger I found a long article by Jeremy Manier of the Chicago Tribune about work being done here in Jersey on songbird migration. The article shows a picture of Princeton professor Martin Wikelski fastening a tiny transmitter weighing less than a paper clip to a white-crowned song sparrow. Wikelski and his colleagues are studying these song sparrows, which spend summers in Alaska. The researchers intercepted a large flock of migrating sparrows during their annual migration south from Alaska through the state of Washington.
Thirty sparrows were captured and brought to New Jersey. In the group of 30, 15 were young sparrows that had never migrated south before. The other 15 were older sparrows that had made the migratory roundtrip at least once before. After being outfitted with their tiny transmitters, the 30 birds were released in New Jersey and their paths followed by tracking the radio signals from a small airplane piloted by Wikelski. The results were surprising.
Both the young and the older groups were obviously confused when first released. However, after a few days and a few dozen miles, both groups figured things out and started heading in a southerly direction. But there was a difference. The youngsters headed directly south, as they were doing when so rudely interrupted in Washington. The older group, however, after their initial confusion, did not go directly south but headed in a southwesterly direction that would take them to their previous winter nesting spots on the Mexico-U.S. border.
The Princeton team was led to a remarkable conclusion. Both the young and older groups have some sort of internal compass that permits them to head in the appropriate direction. However, the older birds not only seem to have the compass but also have acquired what amounts to a “map” of the U.S. They somehow figured out where they were, at least relative to their winter retreat, and what compass heading to use to get there. The younger birds, having no such map, just relied on what may have been a genetically programmed compass heading that simply told them to fly south.
When I visited the Princeton Web site I found an article by Chad Boutin from the Princeton Weekly Bulletin of June 19, 2006 describing how Wikelski and his crew tracked another kind of flying migratory animal, the dragonfly! Wikelsi and his Princeton colleague David Wilcove were down in Cape May, New Jersey watching songbirds migrating when Wilcove pointed out that the birds weren’t the only species migrating overhead. There were the dragonflies, which have been populating Earth for quite a long time, roughly 285 million years. Birds didn’t appear until over a hundred million years later so the possibility exists that the migratory habit was first developed in the insect world.
Wikelski approached Sparrow Systems, a manufacturer of homing devices, to come up with a transmitter that could be attached to a dragonfly and not interfere with its flying capabilities. Sparrow supplied a transmitter weighing about 300 milligrams, only a third the weight of a paper clip. By mixing Superglue with eyelash adhesive, certainly a strange combination, they found they could attach the transmitter to the dragonfly without hurting it. So, in the fall of 2005 they tracked, from the ground and from the air, the flight of a number of migrating dragonflies.
They followed the dragonflies for about two weeks, the life of the batteries in the transmitters, and found a number of similarities shared by both the sparrows and the dragonflies. Both tended to not begin flying until the temperature had dropped two nights in a row. Both would usually fly one day and rest the next. When the dragonflies got to Cape May, they encountered the Delaware Bay, where their straight-line path would take them over a 5-6 mile stretch of water to reach Delaware. After flying over the bay for a short time, they turned back and followed the shoreline until they reached the Delaware River, with a much shorter distance over water to fly. Many songbirds also tend to avoid such major environmental barriers.
As a battery person, I was naturally wondering what battery was used in these mini-transmitters. I tried briefly to find out on the Web but have not as yet succeeded. My guess would be a lithium battery of some sort. I wasn’t surprised when I learned that lithium batteries had flown on various space missions. However, I must admit that I would never have guessed that a lithium battery might fly on a dragonfly!
Allen F. Bortrum
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