[texbirds-freelists] [texbirds] NEXRAD radar observations of migrating birds in the western Gulf coast region, 4/9

The consistent run of extremely low upper air velocities is amazing and
unprecedented in my experience of attempting to analyze NEXRAD imagery over
the past 7 spring seasons. Two (that's 2) kt. at Brownsville sounds like a
rare day ever for late August and unheard of in what is still the first
half of spring migration. All stations were single digits except a 10 kt.at
New Orleans at E to N. Even Merida, Yucatan, was in single digits. There's
not much incentive for staging migrants to launch a trans-Gulf flight under
these conditions as it is a long flight if there are no tail winds to add
to the still-air flight speed of passerines. Some (but not many) have been
doing so, however, and successfully. The familiar conveyor belt of stiff S
to SE winds that carries the trans-Gulf migrants each spring appears to
have broken down. Nevertheless "cyber-birding" the listserves shows that
the usual species are arriving at more-or-less the usual dates (some
notably early) if not in great numbers. You would expect that such a
departure from normal spring weather patterns would produce some notable
phenomenon and it has - pleasant spring birding conditions.


Checking the stations at 13:00 shows some raptor-like flocks in northern
Willacy and central Kenedy Counties in South Texas and a sprinkling of
migrants offshore from the Corpus Christi area. I will check later on to
see if things pick up and update if they do.

John C. Arvin
Research Associate
Gulf Coast Bird Observatory
103 West Hwy 332
Lake Jackson, TX 77566
jarvin@xxxxxxxx
www.gcbo.org

Austin, Texas


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