As Don noted, I was amazed at the number of birds traveling over Cape May Point at height late this afternoon. I didn't get to the Point until after noon today, but even so, I heard Eastern Bluebirds passing over the entire time I was ogling ducks on Lighthouse Pond, while watching very little in the way of raptor migration from the Hawkwatch platform, and while watching 20 Common Eiders at the jetty off the end of Whilldin Avenue in Cape May Point.
But it wasn't until I was joined at the jetty around 3:30 pm by Tom Reed and Sam Galick that I deigned to pay much specific attention to the flights going over my head. That change was occasioned by a flock of 26 Eastern Bluebirds that flew over us relatively low (relative to the height of the other birds flying over) heading in off the bay and toward the north. That flock moved my focus off the water to the sky and we started noting flocks of blackbirds, some very large flocks of blackbirds, very high coming in off the bay and heading northish. We did have a lower flock of 5 Rusty Blackbirds, but the vast majority of birds way up there were, apparently, Red-winged Blackbirds. Some 3200 Red-winged Blackbirds.
As we could see the blue sky behind the front (and could for most of the day, though it still never advanced on us), I opined that these northbound birds might have been migrating behind the front and caught up with it and passed through it to find themselves over the bay whereupon they headed north to land. Of course, that's just a theory, and one with a few holes, the most obvious being the extreme height at which the birds were passing (I'd suspect that if these birds were trying to reach land after finding themselves over water, they'd be at lower altitudes typical of such birds). Regardless, the phenomenon was thought-provoking.
I then headed to CMBO's Northwood Center and, upon leaving it and opening my car door, I noted that there were A LOT OF BIRDS going over! They were all quite high, but one stream of birds, American Robins, was passing by much lower than were the barely-visible blackbirds. Additionally, the robins were heading south, while the blackbirds were heading (as when viewed from the beach) north. In the 15 minutes that I stood by my car with the door open and with chin somewhere around my navel, I estimated some 4000 American Robins to have passed south. I believe that the robins were in active southbound migration and they may be what's "lighting up" the NEXRAD. The blackbird story is still up in the air (no pun intended, or not much, anyway).
I thought that a better vantage point would give me a better handle on the flight (the parking area at the Northwood Center is just a bit constrained in its skyscape), so headed to the Cape May Migratory Bird Refuge, arriving at 4:45 pm. Unfortunately, either the flight was over (or nearly so) or I was now too far east, as I saw only a shimmering south-bound stream of (presumably) robins at one point shortly after arriving in the parking lot. Despite the lack of passerine flight, I decided to stay and hope for owls getting up. While I did find a Great Horned Owl perched on the Osprey platform, it was the only owl that I saw. I also heard two Virginia Rails, though. At 5:45, I called it a day.