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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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