[texbirds] Monitoring spring bird migration using NEXRAD weather radar
- From: "John Arvin" <jarvin@xxxxxxxx>
- To: "New Texbirds" <texbirds@xxxxxxxxxxxxx>, "TX-Ornithology" <TX-ORNITHOLOGY@xxxxxxxxxxxxxxx>, "LABIRD-L" <LABIRD-L@xxxxxxxxxxxxxxxx>
- Date: Sun, 7 Apr 2013 13:35:39 -0500
Upper winds are 30 kts. due south at Brownsville and Corpus. Brownsville
was showing a nice halo signature indication the reflective objects were
passing over the station and continuing northward. Corpus of course is
down. To the northeast Lake Charles has ESE winds at 22 and New Orleans
east at 12. The problem with Brownsville's halo is that objects are moving
only a little faster than posted wind speeds. I like 10 kt. differential to
be sure that birds are involved. However this does follow a common pattern
with birds arriving at Brownsville early, spreading to stations on the
northern Gulf coast later in the day. There is 5 degrees of latitude
difference between Brownsville and northern Gulf stations so arriving
migrants may well be several hours earlier there. There is also the effect,
discovered by Sid Gauthreaux and Carol Belser, of migrants arriving in
extreme southern Texas/northeastern Mexico and then continuing NE over
water toward the upper Texas and southwestern Louisiana coasts - like a
bank shot in a pool game.
Later, at 1:30 p.m. migrants are approaching Houston from the SE through W
and approaching Lake Charles from the SE. No activity was evident at New
Orleans yet. Whether these birds are coming from a touch-down on the South
Texas/NE Mexico coast or are migrants coming straight across the central
Gulf I can't say, but the timing seems right for the former, and at
Brownsville the flight has dwindled.
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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