[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: Tue, 9 Apr 2013 10:37:09 -0500
Wow! Winds at 4000 ft. this morning are 52 kts. at Brownsville, 56 (!) at
Corpus, 39 at Lake Charles, and I wasn't able to get a reading from New
Orleans but expect it to be a little less than at Lake Charles. With
tailwinds like that the average small passerine adds its own flight speed
and you get up to near 100 miles per hour for a Gulf crossing. That puts
migrants on the northern Gulf coast quite early in the day. These winds are
being sucked up into a deep low pressure area in the southern Great Plains.
A couple of questions come up: there must be a maximum tail wind speed
above which birds cannot control flight and it becomes dangerous for them,
but I have never seen any data, or even speculation on that. And blizzard
conditions are advertised in association with this Low. Are birds in danger
of overshooting the survivable terrain into which they are headed? I expect
the violet weather associated with the Low would put them down before the
blizzard condition set in but that is just my speculation.
By 10:00 nice halo signature images were forming at Corpus (back up),
Houston, Lake Charles, and New Orleans indicating that birds were
overflying the radar stations and continuing inland (no surprise there).
This is earlier in the day than we usually see this but of course it is due
to the extreme upper winds. Today will not be a good day to be on the coast
but after frontal passage tomorrow there should be two or three days of
good migrant birding. On the other hand this afternoon might be interesting
well inland as birds begin to precipitate to the ground. Yesterday's heavy
cloud cover looks to be thinning out by midday so diurnal migrants may be a
feature today as well.
Update late if warranted.
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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