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Bob,
 
Of course sheer conjecture here, but Dr. Evans has shown some pretty interesting data from the surveys of nocturnally migrating Dickcissels in the Rio Grande Valley of Texas. Using detections of nocturnal calls picked up across the entire valley here is strong evidence suggesting these birds will circle areas of light pollution. His data showed that all of the more rural data collection sights across the broad front sampled had the same rates of detection and peak timing of detections were the same. Yet over the large population centers (e.g. well lit cities) detections were far greater. At any rate, assuming there is something to this what if the birds were drawn to the bright beacon and circled it over the otherwise dark gulf (much like moths to a flame literally) and just perished out there simply because they ran out of energy?!?...
 
It's a long shot and a stretch I know, and like you said we'll never know. These incidents have occurred annually without any exploding oil rigs as well, but it's always interesting to consider possibilities.
 
Best,
 
Jeff Bouton
Port Charlotte, FL
[log in to unmask]
  

--- On Mon, 4/26/10, Lucy and Bob Duncan <[log in to unmask]> wrote:


From: Lucy and Bob Duncan <[log in to unmask]>
Subject: [FLBIRDS] bird casualties
To: [log in to unmask]
Date: Monday, April 26, 2010, 4:54 PM


Hi all,

    Lucy and I checked the beaches at Ft. Pickens, Escambia Co., extreme NW FL. this morning and found no dead birds. A fisherman who fished the outer beachs there every day last week said he saw none.

    Checking the infrared satellite images last week (thanks to folks who put me on the site) I found nothing that would indicate severe weather in the Gulf. There was some disturbed weather off the west coast of the peninsula but nothing to account for the deaths of pelagic birds that spend most of their lives at sea including facing the severe weather of the southern oceans. They would not be brought down by a strong thunderstorm. Perhaps these deaths, pelagics and passerines, are not related. Maybe the necropsy (by Florida FWC) will show a cause for the pelagic. Furthermore, I monitored land radar stations along the northern Gulf Coast all last week (radar reaching out 120 miles) for possible fallout conditions. There simply were none. It was great weather, with fairly light and variable winds in the northern Gulf. In summary, I do not think this was a weather-related phenomenon.

    If the two are related, pelagics and passerines, then it had to be trauma that reached from the surface to 3000 - 5000 ft, the altitude at which migrants approach the coast. Since the birds washed up on a very strong SE wind, their origin, at least for one day or more, had to be to the SE of the kill. Unless currents brought them to that point earlier from elsewhere. Since the Eglin AFB Test Range extends well out into the Gulf south of Okaloosa and Walton Counties, an explosion or concussion might cause such an event, but I find that unlikely since it's never happened before and would probably be detected on land. 

    That leaves the oil rig explosion. Unless birds were loafing on the rig at the time (and passerines do this on their journey across the Gulf) and pelagics were feeding around the rig, it is highly unlikely that was the source. Were there any signs of burns on the carcasses? Oil? That was not reported. It's also well to the SW of the wash-up. Surely, the birds would have drifted to the LA. coast, not NW FL.

    There is one other possibility. Some migrants originate their journey from South America and southern Central America, making the journey in hops, with stops in the Greater Antilles and Yucatan. Birds have been known to overshoot their destinations. It is possible the casualties overshot Yucatan overnight and found themselves in mid-Gulf, with light winds, no tail winds to assist them on, they simply used their fat reserves and crashed. Did anyone check for fat content on these birds?

    I think this is a mystery which will never be solved.

Bob Duncan
Gulf Breeze, in the western Panhandle


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