Many Tyranni have special “Dawn” or “Twilight” songs. Often these are more complex than their normal song vocalizations. The Acadian Flycatcher, for example, increases the rate at which it utters it typical song and intersperses a variety of chips and metallic notes during its dawn performance. The Eastern Wood-Pewee also increases its rate of singing and introduces a new phrase in addition to its usual “pee-ah-wee” and “peeeoooo”.
On the morning of June 7, 2010, in the predawn hour, I arrived at the boat landing in Wyalusing State Park, Wisconsin, with the aim of recording the songs of Prothonotary, Kentucky, and Yellow-throated Warblers (all specialties of the park). As I got my bearings and starting listening for my target birds, I heard a particularly vociferous Eastern Phoebe performing an extended bout of Dawn Song. I took advantage of the opportunity and stopped to record a portion of it. At the time I did not notice anything unusual about the performance, other than it did seem a little bit more enthusiastic than I was used to hearing. However, when listening to the recording and viewing the sonogram, I noticed something unusual. Normally Eastern Phoebes will alternate their two song phrases, (1) fee-bee and (2) fee-b-be-bee. These are also sometimes designated as RR1 and Rr2. This bird, however, seems to be introducing a third phrase, or at the very least, a well-defined variant of RR1.
RR1 variant (RR1-v). Notice the extra note at the end.
In the recording sample below, the pattern is: Rr2, RR1-v, Rr2, RR1-v, Rr2, RR1, Rr2, RR1-v, Rr2, RR1, Rr2, RR1, Rr2, RR1, Rr2, RR1, Rr2, RR1, Rr2, RR1-v, Rr2, RR1, Rr2, RR1-v, Rr2
Eastern Phoebe Dawn Song Variation
Tallying up all 92 songs this phoebe sang in the 3:09 minutes that I recorded it, there were 21 RR1, 26 RR1-v, and 45 Rr2.
In the somewhat limited research I have conducted, I have not found any mention of this or a similar phenomenon in the vocal behavior of Eastern Phoebes. Similarly, a somewhat cursory search through xeno-canto, Macaulay Library, and the Borror Laboratory online archives, did not turn up anything either. So I don’t believe there is any way to tell at this point if this is just the behavior of an unusual individual, or if it represents a sample of a wider phenomenon. It is definitely something I will be keeping and eye and ear open for in the future.