Date: 5/9/26 10:01 am From: Yaukey, Peter via groups.io <pyaukey...> Subject: [ALbirds] thoughts on fallout morning flight
ALBirders:
There was a large fallout reported at Fort Morgan two days ago, with about 2500 transgulf birds arriving, dominated by Swainson’s Thrush, Redstart, and Maggie. Here is the eBird list https://ebird.org/checklist/S334095331 Many of you are probably aware of a massive fallout in rainy conditions at Dauphin Island on 4/27/23 reportedly involving c. 50,000 birds passing from the island to the mainland, viewed as a skywatch, led by 15,000 Red-eyed Vireos. Here is that list https://ebird.org/checklist/S135307185 The fact that the birds in the latter case were moving northward in daylight onto the mainland, begs the question of what situations lead to fallout birds continuing movement, and what we can do to crack that code so that we could witness such events. The weather map for 7am on 4.27.23 is pasted below. Another stalled front situation, apparently. That frontal boundary is along the northern Gulf coast for the three mornings previous to that map, as well.
In New Orleans, we have large morning flights on the south shore of Lake Pontchartrain in FALL, at its east end (South Pt). In fall the best mornings are 20-30,000 migrants in 2-3 hours. We have known about it since 2002. This appears to be a corrective movement, happening after fall cold fronts, with the birds heading back northward in the morning into the wind, apparently attempting to correct for wind drift the night before.
It wasn’t until about 5 years ago that we discovered that spring flights sometimes happen there too, with as many as 9,000 birds in a morning detected so far (that flight was dominated by Indigos and Blue Grosbeaks). We have only seen four or so of those spring flights, but the mechanism seems to be continued diurnal forward movement of birds that had been grounded in a frontal fallout the night before. They continue northward in the morning (against a headwind), low to minimize the wind resistance, and get deflected by the Pontchartrain shoreline until they come to South Pt and launch across the 5 mile water gap (into the wind).
This begs the question of whether any of the other large water indentations along the northern Gulf have similar concentrating effects. Do the birds continuing north want to go due north, or northeast? Those with a NE inclination, do they accumulate into a larger flow along the western shore of Pascagoula River Marsh, or Mobile Bay, or Escambia Bay?
I spend lots of time in Pensacola, and have contemplated the shorelines of Escambia Bay (and connected features) for some time, but have presumed the water crossings were too short to force birds to deflect instead of crossing. However, out of curiosity last fall, I searched the eBird high counts for Santa Rosa County (which forms the southern edge of the Bay), and there is a fall report (Oct 2002) of 1000 Palm Warblers streaming east along the bayshore in the early AM, akin to what South Point birds do in fall in their approach along the Pontchartrain shoreline. Then, last Nov, I tried out a spot at the southeast corner of the bay (the Tom King Bayou Bridge), and had 3000 robins heading northeast around the corner of the bay, also parallel to the Lake Pontchartrain phenomenon. So, continuing the analogy with Lake Pontchartrain, could there be an exodus of spring fallout birds around the eastern end of the Bay as well? I haven’t been able to free up my schedule on the right mornings to go and check yet, but I am itching to do so.
Bob and Lucy, I know you live near the other corner of the bay; if you have insights to bear on this, I would love to hear them.
Apologies for my verbosity folks,
Peter Yaukey
PS- just because birders have not keyed in on morning flights along these Gulf bays before, doesn’t mean they can’t be happening regularly. Indeed, two of the best morning flight locations on the continent were discovered just in the last decade or so in two of our most heavily birded cities, within the actual city limits, somehow undetected previously (Bear Divide, Los Angeles, and Battery Godfrey on the Presidio in San Francisco).
PPS- yes, I apologized for my verbosity, and then promptly added more. *sigh *
