Having kept track of the passage of Nighthawks over the northeast edge of Columbus Int'l Airport for the past 4 evenings, the final scorecard reads:
Weds 8-24    12 birds
Thurs 8-25  166 birds
Fri 8-26     52 birds
Sat 8-27      4 birds

This likely represents the classic 'first wave' of Nighthawk migrants through central & southern Ohio.  This pulse almost always falls between Aug 24 - 30, with the peak slightly different in different places.  It seems to have several features:
1. It's fairly compressed, with the peak movement often only over 2-3 days. If I had only birded Weds & Sat night, I would never have noticed it this year.
2. The routes favor long blocks of trees.  Around here, that most likely means river and creek riparian strips, but any large blocks of trees will do.  The birds eventually roost in trees when it gets too dark, and perhaps they feel more secure when flying over trees.
3. The birds are silent.  They mostly fly high, until fading light forces them down lower to look for roost limbs.

Now things will quiet down until the Second Wave hits around the 2nd week of September.  With their languid migration pace (only flying during the evening, eating along the way), it's tempting to speculate that the two pluses represent U.S. and Canadian birds, with the delay between them due to the latter's circumnavigation of Lakes Erie or Ontario.  Does anyone know when Nighthawks pass through Pt. Pelee or Holiday Beach?

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