Update: this bird was in the same place when I went back today. The thing that sort of looked like a nest was no longer there, so I'm guessing it wasn't one. A neighbor says it's a Cooper's hawk, but the sound clips I listed to in Merlin did not match the one I recorded with my original post, so a real birder's id would be so helpful. Thank you!
I saved the audio file on my Google Drive, shared the link as "Anyone with link" can view it, and used the link icon in this editor (looks like a paperclip) to link to my file to my post. That way anyone who sees your post here can click on that link to get access to your audio file. Hope this helps!