I just returned from a visit to the Purple Martin roost at the South Shore terminus of the Causeway Bridge. The martin roost usually peaks about this date.
There were approximately 2500 martins coming to roost this evening. As usual, maximum numbers were not visible in the sky until after sunset. As is typical, they swarmed into the roost sites in waves, now and again bursting back out, until they were settled (though still restless when I left in the failing light). They were clinging to the extreme east and west outer faces of the bridge, as well as both faces of interior gap between the northbound and southbound lanes (one can sneak under the bridge on foot to view this area). They were also on at least four of the cement struts that run lengthwise underneath the northbound span.
I approached as closely as ~10 yards from the near edge of the clinging birds, without them flushing.
As last year, I saw no adult males. I wonder where they go?
Online radar shows a much larger echo at the roost site at the Mandeville end of the Causeway, but this site probably does not afford a rewarding birding opportunity, not being accessible on foot, being farther out over the water. Here is the echo from it dispersing on June 30 in the early AM, viewed from the Mobile, AL radar. The donut shape on the north shore of Lake Pontchartrain is distinctive of roost dispersal. Note that the roost at the south end of the Causeway is not even visible- presumably 2500 birds is not big enough to show up!