Thursday, April 17, 2014

Bird exodus on radar last night

The recent cold front seemed to put birds down in a rather patchy way.  Last night the winds had switched to have a southerly component, and (as is typically the case) the birds grounded by the front took the opportunity to leave on the tailwind.

Most songbirds migrate at night- the images below are from 8:15 and 8:53 last night, respectively.  Track the green blob as it moves northwest between the two images.  It indicates an apparent concentration of them taking off from the English Turn area (a large wooded patch), and heading NW at what appears to be about 45 mph (~30 miles in 40 minutes, eyeballing it).  The other light blue, starting in the first pic but greatly expanded in the second, is probably also birds taking off in lower densities and heading north, but could include bugs and other "aerial plankton."

The English Turn concentration is interesting, as someone who lives in a nearby part of Algiers reported their lawn being covered in Indigo Buntings- they may have been on the edge of that concentration of migrants.

Out my window right now (noon) are extensive glowering clouds- a widespread rainfall can act like a cold front, forcing migrants coming north across the Gulf to stop in our area, sometimes in impressive numbers.  Oddly, in good weather with a tailwind, they simply by-pass

us and head inland, too high up for us to see (except on radar).   If the rain is gone by nightfall, they leave the same night (often).

Let's see what happens!


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