Mississippi River skywatch- no tropical cyclone waifs

After leaving Holy Cross this afternoon, I took a short detour to scan the river from the levee adjacent to Tulane's Hebert Center.  Because a load of frigatebirds had come inland not far from this spot during Cindy in June, and Harvey had made landfall in approximately the same location as Cindy near the Texas border, I figured what can happen once can happen twice.

Winds were strong in my face from the (more or less) south- making whitecaps on the water and causing my pant legs to flap vigorously.   I only had binoculars, but a scope would have been useless.  The weather service reported gusts to 35 mph at nearby Alvin Calendar Field while I was there, but it sure felt more like a sustained 30-35 to me!

For the entire half hour I was there (1:40-2:10 pm) there were a dozen or so Black Vultures kiting at various heights along the shoreline to my east, evidently buoyed by winds blowing up river and deflecting up the levee there, where the river makes its sharp turn.  I kept scanning them thinking a frigatebird might be coaxed into enjoying the same updrafts (I have seen this in storm-waif frigates before), but none appeared.

An Anhinga came northwest across the river fairly high up, scarcely making any effort to do anything but let the wind carry it.  Ten on so Chimney Swifts also came across riding the gale, one seemingly on the verge of losing control as the wind bullied it forward.

Several Barn Swallows fought the wind to cross the river southward.  A buffeted Spotted Sandpiper flew by along the shore.   A handful of Laughing Gulls glided up and downstream.  One Caspian Tern flew downstream.  It was the only surprise of the visit- though only mildly unexpected.

The enigma of species missing south of Lake Pontchartrain

Yesterday, Fox 8 posted this video of a beautiful male American Kestrel on one of their cams:

https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.facebook.com%2FFOX8NOLA%2Fvideos%2F10155849050679610%2F&data=01%7C01%7CPYAUKEY%40UNO.EDU%7C8956ab8c8d14495c605508d4e687fc01%7C31d4dbf540044469bfeedf294a9de150%7C0&sdata=TR3TwqrpUx6V%2Fct%2B%2FP5YU25l1zokjgMXo5lXqA2RbG8%3D&reserved=0


Apart from being a real looker, this bird is also of interest because it is here at a curiously early date-  the species nests on the North Shore, but is normally absent on the South Shore in the nesting season.  Being here before the normal fall migration period suggests it may have wandered down here after it finished breeding.  Such post-breeding dispersal in late summer is pretty widespread in North American birds.

But back up a bit.  Why would Kestrels nest on the north side of Lake Pontchartrain, but not the south side?  Isn't there plenty of acceptable habitat down here?  There does appear to be.  However, fully seventeen other species of North Shore nesters are also absent down here despite apparently suitable habitat:
Bobwhite
Wild Turkey
Swallow-tailed Kite
Broad-winged Hawk
Red-tailed Hawk
Belted Kingfisher
Red-headed Woodpecker
Yellow-throated Vireo
Eastern Wood-Pewee
Wood Thrush
Swainson's Warbler
Kentucky Warbler
American Redstart
Yellow-breasted Chat
Summer Tanager
Eastern Towhee
Blue Grosbeak
This used to be true of Eastern Bluebird and Northern Rough-winged Swallow as well, but they have become more regular nesters on the South Shore in recent years (or so it seems to me).  In reverse, the Bobwhite and Kentucky Warbler were more regular as nesters on the south side decades ago than they are today.

Why aren't all these species on the South Shore?  I and others have pondered this for many years, without a really plausible explanation yet emerging.  A biogeographical mystery under our noses!

Peter