[texbirds] Re: Monitoring spring bird migration using NEXRAD weather radar
- From: Rich Kostecke <rkost73@xxxxxxxxx>
- To: "jarvin@xxxxxxxx" <jarvin@xxxxxxxx>, New Texbirds <texbirds@xxxxxxxxxxxxx>
- Date: Sun, 17 Mar 2013 11:07:04 -0700 (PDT)
Sorry about the empty reply. Didn't mean to reply at all but my cell phone
seems to have a mind of its own at times.
Rich
Richard Kostecke, Ph.D.
The Nature Conservancy
318 Congress Ave., Austin, Texas 78701
Email: rkost73@xxxxxxxxx or rkostecke@xxxxxxx
________________________________
From: Rich Kostecke <rkost73@xxxxxxxxx>
To: jarvin@xxxxxxxx; New Texbirds <texbirds@xxxxxxxxxxxxx>
Sent: Sunday, March 17, 2013 12:47 PM
Subject: [texbirds] Re: Monitoring spring bird migration using NEXRAD weather
radar
Sent from my Verizon Wireless Phone
John Arvin <jarvin@xxxxxxxx> wrote:
>For the last several days we have been having the kind of spring weather
>that figuratively sucks up migrating birds and propels them northward
>toward their breeding grounds in sufficient numbers to use NEXRAD weather
>radar to good effect to monitor this movement. I will not go into the
>technicalities of how NEXRAD works because there are many internet sources,
>mosty university sites, that do a far better job than I could in their
>tutorials. But a couple of simple things need to be said: 1) migrating
>birds almost always move with favorable winds. And the winds I am talking
>about are not surface winds but those at higher levels of the atmosphere
>where most birds move when they are headed long distances. It is only when
>they begin a migration flight on favorable conditions only to have those
>conditions deteriorate en route when they cannot easily cease migrating to
>wait for better conditions that they move against winds. The reason is
>obvious. It takes lots more energy to move against winds when moving with
>winds helps conserve energy to complete the journey. Any bicyclist can tell
>you that.
>Then 2) there are times of the day when monitoring NEXRAD is more
>profitable than others, and this depends whether you are birding the coast
>or birding inland. In the latter case, since most over-land migration is at
>night, then clearly night is the time to study this. However, some birds,
>primarily large bodied, long-winged species like cranes, pelicans, and
>raptors using rising air currents off heated ground to provide them the
>lift they need to move long distances in an energy-efficient manner. Some
>ducks, herons, gulls, terns, and shorebirds also migrate during the day if
>conditions make this a viable strategy, although these groups also migrate
>at night under other conditions. Songbirds migrate from south of the Gulf
>of Mexico to the northern Gulf coast in one necessarily non-stop flight
>(Yes, I know there are several thousand offshore petroleum in mostly the
>near-shore Gulf and I spent 3 months on one studying trans-Gulf migration
>with an LSU 3 year project and I can discuss that at length but for now
>I'll let that slide for a while).
>
>Other songbird species, primarily those that winter north of the Isthmus of
>Tehuantepec in southern Mexico, although there are many exceptions to that
>statement, choose a circus-Gulf path in which they migration over land,
>paralleling the coast. These migrate primarily by night (again there are
>exceptions).
>
>3) Timing of migration seasonally: there is a regular progression of suites
>of songbird species throughout the spring migration season, beginning for
>all practical purposes in January with Purple Martins and continuing
>through March when southern breeders arrive (Ruby-throated Hummingbird,
>Chimney Swift, a few early warblers and Yellow-throated Vireo, etc. and
>peaking in mid April through early May with too many species to list. May
>is diverse early but beginning about the 10th the flycatchers are the bulk
>of songbird migrants, especially the Empidonax and pewee groups. The
>seasonal timing of individual species is remarkably consistent year to year
>and if an Empidonax is reported in March then it's time to take a second
>look.
>
>As I have over the past 5 or 6 springs I will post bird movements that I
>detect on NEXRAD when there is something significant visible (not every day
>as in the past). One thing needs to be said. NEXRAD is not a panacea that
>can predict where a migratory flight will land. Often on strong south winds
>migrants may take advantage of the boost to move well inland (50 - 100 or
>more miles) before landing. On the other hand if they encounter bad weather
>en route they may land at the first opportunity, often exhausted, a
>situation that has come to be called a "fallout". These events are much
>anticipated by birders. The classic fallouts of the 50s, 60s and 70s may be
>a thing of the past but a weakened version continues.
>
>So read these bulletins if you want to, and if not, the delete key is
>within easy reach. I may post some particularly illustrative radar images
>to the FB Texbirds site from time to time.
>
>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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