Watch the bow wave for sooty Terns (Long)
Dma3@aol.com
Thu, 27 Aug 1998 18:59:22 EDT
The following probably does not apply to Bonnie at this point, but might be of
interest for the future. The usual scenario for hurricane birding is to find
seabirds trapped in the eye, or ditched on inland lakes and rivers after the
storm has passed, especially east of the eye's track.
I witnessed a different phenomenon during Hurricane Fran. Fran came ashore in
NC on a Thursday night, and charged quickly up the piedmont of VA. Brian
Sullivan (in BIRDING) has described the wonderful fallout of birds he and
other observed at Kerr Reservoir on Friday morning. At noon on Friday I was at
Black Hill (Little Seneca) Reservoir, on the Montgomery CO piedmont. Fran was
still 150-200 miles SW of me in VA. Winds at my location were gusting to
40mph, from the SE, with bands of light rain. I was not really expecting
anything to happen until the remnants of Fran passed by, forecast for about
10PM Friday. I was surprised to see 2 Sooty
Terns come in from the south, drop low as they neared the lake, make a few
quick circles, and drift off to the north. They were at the lake for about two
minutes.
The tern's flight style told the story. There was no frantic struggling or
flailing in the wind. They hung suspended in the storm, pointed towards the
NE, making occasional languid strokes. A few times they turned SE into the
wind and made a few more powerful strokes, before again turning NE to rest.
The flight looked graceful and easy. The combination of the wind blowing NW,
and their flight to the NE, produced a net vector heading of roughly North.
They had probably been over land for at least 12 hours at this point. They
looked like they could go on much longer.
I believe that the terns knew approximately where the ocean was, and were
trying to reach it with a minimum expenditure of energy. They were displaced
ahead of Fran, riding the storm's bow wave.
I envision a band of seabirds riding ahead of the storm beginning about where
the tropical storm force winds begin, say 100-200 miles from the center,
depending on the storm's size. The Weather Channel shows this as an oblong
yellow oval . I think of it as the zone where seabirds are most likely to be
trapped, with most concentrated in the NE quadrant. I saw the Sooty Terns when
the edge of that oval reached Germantown, long before the storm center passed.
Being on a body of water is probably not essential, although my experience,
(and Dave Abbott's in nearby Loudon Co VA), suggests that birds will try to
concentrate at water. The Sooties would have passed over very high, and might
have been missed, if they had not dropped down to check the lake.
I don't think that birds trapped in the yellow zone are necessarily doomed. It
depends on the storm track, and how long they are forced to spend over land
and in the air. Perhaps they can gradually work their way out. Perhaps birds
nearer the center can simply ride counter-clockwise around the eye until they
reach the south
side of the storm, where winds are weaker, and they have a tailwind to the
ocean. Perhaps that is what happens when a storm like Bonnie stalls. Any
thoughts?
Dave Czaplak
dma3@aol.com