This is the evening song of the Acadian Flycatcher. Perhaps we should start by recognizing how unusual this recording is. First, because, evening song is not used on a daily basis. I have sought it often without success. Second, because insect noise isn't competing for our attention. Typically, when I luck out and encounter this common species singing this uncommon song, insects are also singing, loudly. It is a denizen of swamps, you know. And that's where I found this bird, in the swamp across the Lumber River from the canoe dock at the State Park Campground. This song comes after the other day birds have gone silent, often well into the period we call night. Barred Owls could be hooting while he is singing, as well as another diurnal flycatcher, the Great Crested one, one of which punctuates the Acadian's performance here with his own, in a lower register.
After you have enjoyed the simplicity of this scene, the two birds singing in their flycatcher way and the river quietly flowing by, let's take a look at its understated complexity. The very first note, let's call it A, is repeated several times. The sixth and seventh notes are different. They always occur together, so let's call them, collectively, B. Then comes another string of A's. Were you expecting B again? Well, it's dusk not dawn, and at this time we get something else, a peaked note we'll call C, and then a smaller peaked note followed by a little buzz, which we'll call, collectively, D. The base syntax of the evening song of the Acadian Flycatcher is [[A]AB[A]ACD]. Each bracket signifies possible repetition of the unit inside it, i.e., repeat A, sing AB, repeat A, sing ACD, do it all over again, and again, etc. It's not mechanical, just rule-bound. This bird breaks the rule by repeating the [A]AB sequence at 0:26-0:32, and he repeats CD instead of singing BCD at 0:38. But he's a pretty regular singer.
The evening song of the Acadian Flycatcher is rich with associations for the human student, and probably for every Acadian Flycatcher on the planet. Dawnsong is the same as above, minus the CD phrases, i.e., it's [[A]AB]. Furthermore, the daysong, the one most birders know, is just a squeezed together version of AB. And C, well that's the common call note, which is also heard throughout the day. In other words, the evening song and dawnsong are combinatorial, they're combinations of discrete, smaller units. Other empids have dawnsongs with exactly the same syntax as Acadian's, but none to my knowledge alternates terminal phrases as this bird does in the evening. So, he's the king of complexity for the empids, although equalled in syntactical virtuosity by Say's Phoebe, a close relative. They however, must bow to the little Tufted Flycatcher. Wait until you hear it.