The crickets almost did me in. In August the population of crickets around my house was a tumult of sound. No matter how or where I set the microphone I use for recording the calls of nocturnally migrating birds, the automatic detection software would quickly be overwhelmed and shut down. I would stand outside and hear hundreds of bird calls in an hour amounting to thousands over a night. But the detectors would only record a hundred calls on the best nights.
I tried different microphones, different locations, different pre-amps and cordsâ€”one night I even ran the thrush detector and the warbler/sparrow detector software on two different computers at the same time.
I did pick up some interesting calls on the nights when I was able to get anything at allâ€”Veery, Canada Warblers, Wood Thrushes, and American Redstarts in mid-August, a Dickcissel later in August with Rose-breasted Grosbeaks and Bobolinks.
But to know that there were so many more birds going over than the computer detectors could pick-up because of the din of cricket noise was starting to make me crazy. My own ears could easily filter out the cricket sounds so that the nocturnal bird calls were clear and strident. It’s nice to see sometimes that the human brain is still much better at some things than a computer.
So at the beginning of September I decided to go back to the old-fashioned wayâ€”sitting on the porch with my ears to the sky as I had done for years before my microphone came along. It was very relaxing and enjoyable to sit in the dark and listen for a few minutes or an hour before bed. Of course I still wondered what might be going over in the hours while I was asleep but September was warmer than normal and that meant the cricket chorus had not diminished. I knew that putting up the microphone again would only lead to more disappointment and wasted late nights playing with cords and amps.
And then it came.
A cold front down from Canada with a wonderful bubble of still, cold air that descended on the state like a blanket. Crickets are insects and when insects get cold they slow down. These crickets got so cold that by the middle of the night they stopped chirping entirely. The cold front also ushered in a wave of migrants, probably most of them from the Boreal. This late September night (Sept. 25th to be exact) the calls of birds rained down clear and sharp from the sky. Tonight there was no chatter of crickets echoing across the neighborhood.
I had the microphone set up in a flash. I still wrapped it in foam and put it up on the roof just in case one of the crickets found a warm spot near the foundation. But it was bird calls only that nightâ€”and lots of them. Nearly 700 by dawn with perhaps a hundred or so Swainson’s Thrushes among them and a few Gray-cheeked Thrushes as well. The next night was nearly as good with about 600 calls. Again the thrushes were mostly Swainson’s with a few Gray-cheeks.
Tonight (9/28) as I write this at my kitchen table, I have the speaker set next to me to listen to the calls from the microphone on the roof. The spring peeper like calls of Swainson’s Thrushes ring out into the house. When you consider that the Boreal may support something like 80 million of them, it’s not surprising that they are so abundant in nocturnal migration here. Another person who runs a nocturnal call detector in upstate New York reported a big flight of Swainson’s and Gray-cheeked Thrushes on September 25th when he recorded 224 calls about evenly divided between the two species.
These birds are headed to Central and South America for the winter where they will become integral members of tropical bird communities and ecosystems. Imagine the role that 80 million Swainson’s Thrushes may play in the tropical forests where they feed on fruiting trees and help disperse the seeds of various tree species.
I am headed south myself in a few days for the North American Ornithological Conference in Veracruz, Mexico where we have scheduled a symposium to bring together researchers to talk about the birds of the Boreal and begin to learn more about the connections these birds make across the ecosystems of the Americas. Maybe I’ll see a Swainson’s Thrush while I’m there.