At the tail-end of the Common Nighthawk migration, birders in Wisconsin can still catch these birds through mid-October, though with waning numbers. The true peak nighthawk season is late August in Wisconsin, depicted in the eBird abundance animation which you can see below, dated August 31.
Common Nighthawk abundance on August 31, 2022
My observations match with the more general statewide average. This year, I saw dozens of nighthawks in their abrupt, banking flight over Interstate 94. I also saw large congregations flying south over the Crawfish River in early September.
The Common Nighthawk flight is nearly unmistakable—I’m shocked they’re even able to fly anywhere, let alone the Amazon Rainforest over winter, since their meandering flight indicates a ceaseless wave of insects to catch on the wing. In this way, the nighthawks resemble a curious naturalist: a birder or botanist mile can probably quintuple the time it takes a brisk mile long walk. But even with their preoccupation with the feeding frenzy in the air, nighthawks are a joy to watch, and pretty easy to identify because of their unique flight pattern and white wing bars.
Common Nighthawk with clear white bars on its underwings. Photo by Andy Reago & Chrissy McClarren
Common Nighthawks prefer sandy and gravelly oak barrens, sand prairies, and gravel urban rooftops for nesting. Many of the confirmations from Wisconsin’s Breeding Bird Atlas II came from urban areas in southern Wisconsin. The birds have seen steep declines according to the North American Breeding Bird Survey, with declines of at least 60% since the 1960’s. Possible causes of this decline include habitat loss, forest fragmentation and mesification, and pesticides that can reduce insect populations.
One study in Wisconsin found that urban nighthawks populations correlate with larger urban areas, with more and larger gravel rooftops, and with high Chimney Swift populations. In addition, these metropolitan nighthawks also had a negative correlation with agricultural area. If you’re out watching for Chimney Swifts in the evening, keep an eye out for nighthawks as well.
Common Nighthawk perched on a branch in day. Photo by Kelly Colgan Azar
You can find nighthawks in migration at Faville Grove, with peaks in May and late August. Common Nighthawks have stuck around through the summer in certain years, and may be breeding in the area. With a number of sand prairie and oak savanna restorations, more and more habitat may be suitable at Faville Grove. The Lake Mills Ledge, a quartzite barrens with scattered oak trees, might entice nighthawks to nest on the open bedrock glades.
Written by Drew Harry, Faville Grove Sanctuary land steward
Cover photo by Putneypics FCC
