Angels. That's what meteorologists and defense workers called these then-strange signals showing up on radar at night when it was clear there was no precipitation involved. It was a real national security problem during an era when aerial attacks on the U.S. had happened (Pearl Harbor) and could happen again.
Then, in the 1950's, meterologists and ornithologists figured it out. The angels are birds. The linked article is worth a look.
By 1:00 a.m., any nocturnal migrant bird that is going to migrate this day is in the air, so that's a good time to check the radar. http://weather.rap.ucar.edu/radar/ And migration was on last night, warblers and others in the thousands, and thousands were seen this morning in morning flight at Higbee Beach, Cape May NJ, and other points, e.g. my favorite watch points along the Delaware Bay.
In contrast, above is the 1:00 a.m. radar from the night before last, showing pretty much jack sh. . . .I mean, there wasn't much flying, and instead of the 3500+ warblers I counted this morning, yesterday (Monday October 3) I counted 32.
[Above, nationwide radar last night at 1:00 a.m. EDT. It was rocking in the eastern half of the country on northeast winds, and on the fact that, hey, it's October, we've got to go.]
[Above, my FOS (first of season) Eastern Meadowlark, in the mist of the bayshore this morning.]
[The beloved Yellow-rumped Warbler, above, came in second numbers-wise today. This one shows the yellow crown that gives the bird its scientific species name, coronata.]
Years and years ago, I was birding Cape May with Paul Lehman, and we saw a Yellow-rumped Warbler, and Paul remarked with a bit of sadness in his voice, "The beginning of the end." When the time of Yellow-rumpeds is here, the time of the big, diverse warbler flights is done for the year. But - big flights of short-distance migrants are ahead.
Oh, the smoke signal thing. My phone quit me this morning, which in some ways is quite a relief, but meant that until I got it fixed, I was removed from the bird communication network of Cape May, one of the hallmarks of this great place to watch birds. Had to find 'em on my own for a while, though I did email friends asking for smoke signals if a hot bird appeared.