18 September 2022
If you’re awake one to two hours before dawn on a calm September night, put your ear to the sky and you may hear birds calling overhead in the dark.
Millions of birds migrate at night and call in flight to maintain contact with their fellow travelers. In the one-to-two hours before dawn they begin their descent and are easier to hear but it takes dedication or insomnia to be awake during those prime sleeping hours.
Fortunately with the advent of microphones, recording devices and sonogram technology, ornithologists and amateurs have recorded nocturnal flight calls (NFC) and can identify who’s calling as they fly by. The sonograms are like fingerprints for each species and can be compared at this quick reference website, NocturnalFlightCalls.com, announced this month by Tessa Rhinehart at the University of Pittsburgh’s @KitzesLab.
Many calls, especially those of warblers, are so high-pitched that they are outside my range of hearing so here are three examples of some easily audible nocturnal flight calls.
The Swainson’s thrush (Catharus ustulatus), above, has such a distinctive flight call that you can identify it in the dark by sound. All About Birds describes the call as a hollow peep that resembles the call of a spring peeper frog.
The rose-breasted grosbeak (Pheucticus ludovicianus) repeats a single rough whistle.
Click here for a clearer version of the rose-breasted grosbeak flight call that was “photo-bombed” by a killdeer.
Though it is extremely unlikely to hear a dickcissel (Spiza americana) fly over Pennsylvania, this sound is so distinct that it’s worth a listen.
Leanr more about nocturnal flight calls at Nocturnal Flight Call FAQs from David Brown. He recorded dickcissels during the 2017 irruption over Montoursville, PA.
Make your own NFC recorder using a microphone, a dinner plate, a bucket and a computer. Instructions and information at Nemesis Bird’s Night Flight Call primer. (This article may be as old as 2012.)
Know which nights will be good for listening by checking BirdCast’s migration forecast.
(photos from Wikimedia Commons, Cris Hamilton and Anthony Bruno; recordings embedded from Xeno Canto)