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Posted by Alex Harper on 10:17:04 04/05/11
Strong south winds out of the Yucatan and Cuba probably prompted a lot of neotropical migrants to make the big step north into the Southeastern U.S. Along the way, most birds heading in a north to northwest vector hit a strong, cold and dense pressure system approaching from the northwest and heading southeast. It appears that on the radar that most winds along the front are shearing towards the northeast, so any birds meeting that front rode that wind perpendicular towards Florida's gulf coast. Where they will end up on the Gulf... I don't know, I'm no Bob Duncan.
Birds typically begin their migration 30-60 minutes after sunset, so birds that left last night probably hit the front in the early morning (it passed through Pensacola at about 11:30 pm EST). Under clear conditions, birds crossing the Gulf reach the coast by around 11:00 a.m EST, but the initial strong south winds and frontal northwest winds add more to consider. If the front that is to pass through Miami would have arrived around midnight last night, Toe would probably be content. I do think the polar region has a few more fronts in store considering it is only April 5. Fingers crossed.
March 31 and April 1 brought birds to the Pensacola area due to a change in wind direction the night of March 30. I was able to tally 13 warbler species on April 1, and although there were fewer migrants on April 2, I found a Nashville Warbler to make 14 species over the weekend. If my Ecology lab does not last the projected four hours a scheduled, I'll head out to Ft. Pickens for some groundtruthing.
And something that I find interesting that I think that is worth sharing: the neotropic migrants we all are seeking out are likely all originated in the diversity-rich tropics. When the Gulf of Mexico was smaller and the glaciers in North America began to recede, species dispersed into North America, colonized, and the cutoff in genetic flow allowed for speciation. When the North American continent continued to warm, more speciation between "our" birds occurred, and as the Gulf widened, the neotropical migrants evolve over time to become for physiologically fit for longer journeys. Lastly, the same south winds in the spring Bermuda or Azore High) aggravating some of us for allowing birds to pass right over (why would they stop when it really is about "survival of the fittest"? The first to arrive get the worm, the territory, and the girl) allows them to make such journeys. That is B.A. Did I miss anything Carlos?
Alex
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