Charles and adjacent Fort Polk had much of a show except for the always
entertaining Mexican Freetail Bat emergence on the San Antonio and Del Rio
NEXRAD sites. To view bird or bat liftoffs go to
http://weather.rap.ucar.edu/radar/ about an hour after local sunset. It
opens with a map of the US showing the locations of the NEXRAD sites.
Choose "regional reflectivity" in the first column and then click in the
general vicinity of the area of interest (west of San Antonio, abbreviated
EWX for the bats; around the central Texas coast between Corpus and
Houston for birds). Then skip to column 3 and select 2 hour loop duration.
It will take a minute or two to load the images. When loaced you will get
radar imagery over the previous two hour period. Liftoffs of birds (and
insects and bats) begin just after dark and you can watch the reflectance
blossoming out like flowers.
A word about timing. Trans-Gulf migrants leave the southern shores of the
Gulf of Mexico and northwestern Caribbean Sea at dusk and fly overnight.
They mostly arrive over the northern Gulf coast between mid morning and mid
afternoon the following day depending on the speed of the upper level tail
winds they use to propel them and keep fuel (stored fat) consumption to a
minimum If they encounter poor weather en route their arrival may be
delayed hours, sometimes many hours. Circum-Gulf migrants in the songbird
and near-songbird groups migrate at night over land. Many species of shore
and waterbirds migrate overland or over water in the daytime.
At 11 a.m. a large area of light rain extended from near San Antonio
northward to NC Texas and was slowly moving eastward. South of the rain
kettle-and-glide migrants were headed N from Brownsville to the southern
edge of Kenedy County. Other flocks are noted just S of Alice and generally
west of Corpus. By noon bird echoes were visible approaching shore south of
Galveston and Lake Charles. Whether the approaching rain will cause a
fallout is yet to be seen. It is moving very slowly eastward.
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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