February 27, 2008
 |
Dr.
David Aborn |
Dear Students:
Here in southeast Tennessee we got a dusting of snow last night, but signs of spring are around. In January, bluebirds were checking out some of the next boxes I have in my yard. Last week, I heard the first cardinals singing. The most exciting sign of spring, however, is that migration is underway!
Bird
Migration Depends on Right Weather
This spring, I will teach you how to read a weather map to
try to predict areas of the country that might see large numbers of
migrants landing. Just like airplane pilots (and passengers, for that
matter!), birds like clear skies for finding their way, and tail
winds to help push them along. Therefore,
when they have southerly winds, birds can fly a lot farther. When the
winds come from the north, or when bad weather comes up, birds will
be forced to land. Since north winds follow cold fronts, birds
will be forced to land immediately following the passage of a cold front.
After the high pressure
area bringing
those winds has moved east, usually a day or two later, the birds have
tailwinds and take off again.
First:
How to Read a Weather Map
You can get
a clear understanding of the words I used above with this lesson on how
to read a weather map. The reward is that you'll learn how you can use
that information to forecast bird migration!
Early
Migrants Starting to Arrive!
Prior to
the front that moved through yesterday, the temperatures had been
very mild (50's-60's), thanks to southerly winds. That allowed some
of the very early migrants to make their way from the tropics to North
America. Birders
in Florida reported their first Purple Martins, Georgia reported Yellow-throated
Warblers along the coast, and someone along the Alabama coast saw the first
Parula Warbler of the year.
With the change in winds, migration has been stopped in its tracks ... much to the benefit of those of us in Tennessee! We have our first martins, as well as some Tree Swallows. This is just a small sample of what will be coming over the next several weeks.
What to Expect This Week
So what about this
week? Take a look at today's weather map for clues. No fronts
are on the horizon, so once this high pressure area moves
east,
winds
will
shift
around to the south (tail winds), allowing birds
that are hear to continue north, and a new influx of birds from the
tropics
to
arrive:
 |
It is too early
to see a large number of birds arriving, but I expect there will
be an increase in the number of swallows, martins, and some of
the early warblers. Dust off your binoculars and start practicing!
Take Care.
David Aborn
North
Chickamauga Creek Conservancy
Chattanooga, TN
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